NorthStar AGM battery charging and sulfation woes with Optima® Digital 1200 Battery Charger.

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Apr 25, 2017
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I have two vehicles and I don't drive either one of them very much. One is inside a garage and the other is outside. The one inside the garage I leave on an Optima® Digital 1200 Battery Charger all the time. The other one I put on an Optima® Digital 1200 Battery Charger approximately once per week. Both vehicles have NorthStar AGM batteries in them. Both batteries are approximately two years old. Normally the Optima® Digital 1200 Battery Chargers sit at 75% for some long time and then they rapidly complete charging of the battery. With the vehicle I leave outside it takes much longer to charge the battery, which makes sense because I charge it less frequently (only once per week). The aspect which concerns me, however, is that now the battery won't go above 75% after more than two days of charging. The battery is only two years old and it was fully charged the previous week. I'm assuming the Optima® Digital 1200 Battery Charger is working properly (I have two of them.) so I am wondering whether the battery is failing already? One would hope that a new $300 NorthStar AGM battery that was charged weekly would last much longer than this. (It has a 5-year, free-replacement, warranty.) I try to buy good equipment so that I am less likely to have a failure, but my current strategy doesn't seem to be working very well. Waiting 10 hours to have the battery charge was frustrating, but at least it always charged fully eventually. Now I have waited more than 20 hours over two days and it still hasn't budged from 75%. Then, I put that same battery on a different charger (NOCO® Genius® PRO 25) and, in fifteen minutes, it showed full. I put the Optima® Digital 1200 Battery Charger back on and it still hangs at 75%. As I said above, I assume the battery charger is functioning correctly, so my only alternative is that the NorthStar AGM battery has prematurely failed. Has anybody else had these sorts of desulfation problems?
 
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Trying to judge the health of a battery by what some charger is doing, or not doing, is not wise.

Do you know how much amperage the battery is accepting at the voltage the charging source is holding it at?
Do you know how much voltage the battery is able to maintain when starting the overnight cold engine?

If the charging source is holding the battery at 14.4 to 14.8v, and the amperage tapers to very low levels, like 0.3 or less amps, then the battery can be considered in the 99%+ charged range. If it is still accepting one amp at 14.7v it will likely require being held at 14.7v for another 45 minutes minimum before 99%+ can be assumed.

An AGM cannot be tested for state of charge at lesser voltages than 14.4v. One needs to know how much amperage it accepts at absorption voltage( 14.4 to 14.8v, not 13.6v.

If the battery, when measuring voltage at the battery terminals sampling voltage at least 2 times a second can maintain 11+ volts when starting the overnight cold engine, it is still healthy.

Northstar AGMS, in my experience, get a bit lazy and petulant when they are not worked hard, and just kept at higher states of charge. Mine, when living the easy life, just engine starting and slight self discharge between starts, then asked to work a bit harder say powering a laptop for 10 hours, do not hold the voltage I expect considering the load or the duration I apply it.

When I take the battery to 12.2v under load over 6 to 10 hours, which is in the 50% charged range, and then high amp recharge, using 35+ amps until voltage hits 14.7v, then i hold the battery at 14.7v until amps taper to less than 0.4, all immediate subsequent discharges it is able to hold higher voltage for longer and it also spins the engine quicker as it holds higher voltage during engine cranking as well.

From 50% to 100% is basically no less than 6 hours, and that assumes the charging source has 20+ amps available initially, to raise voltage to 14.7v within the first hour.

I use an adjustable voltage power supply with a voltmeter, ammeter, and amp hour counter on the DC output.
When I put such meters on a smart charger, I am always disappointed as the charging is always 'smart' terminated too quickly, well before the battery is 100%.

From 80% charged to 100% charged takes no less than 3.5 hours with lead acid batteries, and that assumes a healthy battery being held at 14.4 to 14.8v for that entire time.
Lesser voltages and less healthy batteries can increase that time exponentially.

If you do not know how much amperage the battery is accepting at the voltage the charger is holding, you do not know the state of charge.

If you do not know how much electrical pressure( voltage) the battery can maintain when spinning the starter, or a similarly large but short lived load, like a carbon pile load tester, you do not know its remaining health of the battery.

To know the true remaining amp/hour capacity of a battery. one would need to fully charge the 100 amp hour battery, apply an exact 5 amp load, and if it can power that load for 20 hours before voltage falls to 10.5v, then it still has 100 amp hours of capacity. The battery also needs to be held at 77f. This test is more applicable to a deep cycle battery. the carbon pile load test is a better way to judge whether a starting battery is still healthy enough for its task.

The Northstar AGM is a deep cycle AND starting battery. How much voltage it maintains powering a starter for 3 seconds is a bit different than powering a 5 amp load for 10 hours. If one does not need the ability to intentionally cycle deeper, and also does not have the ability to truly fully recharge, their money is largely wasted on a TPPL AGM like Northstar/Odyssey.

These high $$ AGM batteries are not immune to chronic undercharging, and those who intentionally deep cycle AGMS know that they are more petulant and live shorter lifespans than their cheaper flooded deep cycle counterparts, unless they are truly fully charged regularly.

Trying to guess at the remaining health of your battery, by what the smart charger is proclaiming, is a lesson in deranged futility.
It's like trying to understand an hysterical woman. You can spend weeks guessing, trying to find patterns, postulating logical hypothesis', and still always be wrong, and more wrong each time.

A DC clamp on ammeter showing how much amperage the battery is accepting at the charge voltage reaching the battery terminals, will yield a million times more information as to state of health and state of charge, without the induced insanity.
 
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ABSORBED GLASS MATT, AGM, is like toilet paper, that's what a Factory rep once told me. they are so different and quite easy to blow hole in the Matt with too much charge current.
 
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I considered the Northstar AGM for my boat. After much research, I concluded it was not a good choice for an application like yours where it sits for long periods, is lightly used, never drawn down and never charged at high amp rates. They simply do not do well in an easy application, and certainly are not a value in that application.
 

jmegas

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Apr 25, 2017
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I've used this Optima® Digital 1200 Battery Charger for a few years and it has always seemed to work well. I did run a 4-hour "Repair Cycle" on the battery with the NOCO® Genius® PRO 25 (I just bought this charger.) and it completed "successfully." I guess I am going to have to start monitoring some technical internal aspects of the battery itself, but I am not all that technical. I do have a Foxwell BT-715 Battery Analyzer which I will have to learn how to use. I have no doubt that the battery is now "charged," the question is whether it is also desulfated? The Optima® Digital 1200 Battery Charger was telling me no and the NOCO® Genius® PRO 25 said yes. They could both be correct, but this is still confusing. Is the Optima® Digital 1200 Battery Charger really not useful? It was a well-rated battery charger. I called Optima® and they said they think the NorthStar battery is at fault.
 
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jmegas

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Apr 25, 2017
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Trying to judge the health of a battery by what some charger is doing, or not doing, is not wise.

Do you know how much amperage the battery is accepting at the voltage the charging source is holding it at?
Do you know how much voltage the battery is able to maintain when starting the overnight cold engine?

If the charging source is holding the battery at 14.4 to 14.8v, and the amperage tapers to very low levels, like 0.3 or less amps, then the battery can be considered in the 99%+ charged range. If it is still accepting one amp at 14.7v it will likely require being held at 14.7v for another 45 minutes minimum before 99%+ can be assumed.

An AGM cannot be tested for state of charge at lesser voltages than 14.4v. One needs to know how much amperage it accepts at absorption voltage( 14.4 to 14.8v, not 13.6v.

If the battery, when measuring voltage at the battery terminals sampling voltage at least 2 times a second can maintain 11+ volts when starting the overnight cold engine, it is still healthy.

Northstar AGMS, in my experience, get a bit lazy and petulant when they are not worked hard, and just kept at higher states of charge. Mine, when living the easy life, just engine starting and slight self discharge between starts, then asked to work a bit harder say powering a laptop for 10 hours, do not hold the voltage I expect considering the load or the duration I apply it.

When I take the battery to 12.2v under load over 6 to 10 hours, which is in the 50% charged range, and then high amp recharge, using 35+ amps until voltage hits 14.7v, then i hold the battery at 14.7v until amps taper to less than 0.4, all immediate subsequent discharges it is able to hold higher voltage for longer and it also spins the engine quicker as it holds higher voltage during engine cranking as well.

From 50% to 100% is basically no less than 6 hours, and that assumes the charging source has 20+ amps available initially, to raise voltage to 14.7v within the first hour.

I use an adjustable voltage power supply with a voltmeter, ammeter, and amp hour counter on the DC output.
When I put such meters on a smart charger, I am always disappointed as the charging is always 'smart' terminated too quickly, well before the battery is 100%.

From 80% charged to 100% charged takes no less than 3.5 hours with lead acid batteries, and that assumes a healthy battery being held at 14.4 to 14.8v for that entire time.
Lesser voltages and less healthy batteries can increase that time exponentially.

If you do not know how much amperage the battery is accepting at the voltage the charger is holding, you do not know the state of charge.

If you do not know how much electrical pressure( voltage) the battery can maintain when spinning the starter, or a similarly large but short lived load, like a carbon pile load tester, you do not know its remaining health of the battery.

To know the true remaining amp/hour capacity of a battery. one would need to fully charge the 100 amp hour battery, apply an exact 5 amp load, and if it can power that load for 20 hours before voltage falls to 10.5v, then it still has 100 amp hours of capacity. The battery also needs to be held at 77f. This test is more applicable to a deep cycle battery. the carbon pile load test is a better way to judge whether a starting battery is still healthy enough for its task.

The Northstar AGM is a deep cycle AND starting battery. How much voltage it maintains powering a starter for 3 seconds is a bit different than powering a 5 amp load for 10 hours. If one does not need the ability to intentionally cycle deeper, and also does not have the ability to truly fully recharge, their money is largely wasted on a TPPL AGM like Northstar/Odyssey.

These high $$ AGM batteries are not immune to chronic undercharging, and those who intentionally deep cycle AGMS know that they are more petulant and live shorter lifespans than their cheaper flooded deep cycle counterparts, unless they are truly fully charged regularly.

Trying to guess at the remaining health of your battery, by what the smart charger is proclaiming, is a lesson in deranged futility.
It's like trying to understand an hysterical woman. You can spend weeks guessing, trying to find patterns, postulating logical hypothesis', and still always be wrong, and more wrong each time.

A DC clamp on ammeter showing how much amperage the battery is accepting at the charge voltage reaching the battery terminals, will yield a million times more information as to state of health and state of charge, without the induced insanity.
Thank you for this long, and I'm confident, very accurate, response. You obviously know far more about both batteries and electricity than do I. I think, from your response, I'm going to need more help in accurately diagnosing the problem because, although I have the equipment, I lack the brains to figure out what is going on. Thank you again!
 
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There is no proof that there is anything wrong with your battery(s).

Smart chargers are not really smart. They largely follow a one size fits all algorithm, and the rest of the effort is expended in extra special marketing claiming how great they are.

On this forum, like many products, they are given godlike status with no proof whatsoever that they do what they claim to do.

The lead acid battery lives it longest life when it is truly fully charged and kept cool.

There is a huge difference between good enough/charged enough to start the engine, and truly fully charged.

TPPL Agms like Northstar and Odyssey are impressive batteries, huge CCA numbers and can gobble up as much amperage as you likely can muster,/ throw at them, just limit the voltage to 14.8v and reduce this voltage the hotter the battery is over 77f/25c.

TPPL AGMs can also be deeply cycled, but when deeply cycled, they need the high amp recharge from their most depleted state, perhaps not each and every deep cycle, but at least once every 6 or 7 deep cycles. If they do not get this they will lose their ability to perform, and without the true full recharge this loss of capacity and performance only increases its rate. It is unlikely this lost performance can be recovered, but by all means try, just don't expect stage 8 super fellate smart charger's ' reconditioning cycle' means the battery is actually improved, especially if one does not know how high the voltage got, how much amperage the battery accepted at those voltages, and how long the elevated voltages were held.

By and large a smart chargers green light only means the battery is charged enough to start he vehicle and or that the battery charger has stopped charging at voltages above float. it does not mean the battery is truly fully charged.

I've fed my group 31 northstar (103ah capacity) as much as 134 amps when it was depleted to ~40% state of charge.

Lesser, cheaper AGMS will say to limit charge amperage to 27 to 33 amps per 100 amp hours of capacity.

The Deka Intimidator is likely the most rebranded AGM battery available, and a Bitog favorite. It will say to limit charging current to C/3, which is 1/3 the amp hour capacity rating or 33 amps for an ~ 100 amp hour group 27.
It could be a perfectly good AGm for dedicated engine starting, with the rare deep cycle here and there, but in deep cycle usage it falls well short of the other higher $$ agms in performance retainment, even when promptly and properly recharged.

The Deka intimidator says to limit to 30 amps per 100Ah of capacity. I have a 5 year old pair of Deka intimidator golf cart batteries at 190 amp hours capacity.
According to Deka, do not charge them at more than 57 amps. yet They will still easily accept 120 amps when discharged to the 50% range, and do not heat excessively when I do this, and they still perform well.

Odyssey AGM outright states no less than a 0.4C charge rate in deep cycle use, meaning no less than 40 amps for their 100 amp hour group 31.
Lifeline AGM, which is pretty much top dog deep cycle AGM also states the more charging amperage, the better, page 20 in the link below.

I've found Northstar documantation to be lacking, and always followed Odyssey recommendations.

When I spoke to an odyssey engineer a while back he was adamant that if the long term float voltage applied from a float or maintenance charger was not 13.6v, at 77f, then it should not be floated long term. Lots of so called 'maintenance' charger will float at 13.2, even on the AGM setting. Floating at too low a voltage for a long time is not a good thing, but especially when there is a significant parasitic load on the DC system.
Floating too high a voltage is overcharging and causes positive plate degradation and flooded batteries will use a lot more water.

On my own system:
If I float my Northstar at 13.6v exactly in the 70f temp range, then crank voltage to 14.8, amps quickly taper to 0.5 or less, usually much less, indicating this float voltage kept the battery truly fully charged.

If I float it at 13.5v in the same temp range, for a day or 2, then crank voltage upto 14.8v, amps will go up above 5 and over 25 minutes taper to the 0.5 range and take another half hour to taper to 0.2. This indicates the 0.1v float voltage difference, allowed the battery to discharge slightly, also proving just how important the float voltage be right for the specific battery.

Note than some AGMs say 13.2 to 13.4 float, others are 13.6 and I think I even saw one was 13.8v all at 77f/25c degrees.
So even if a smart charger has a specific setting for AGM, if the float voltage it holds is too low, the battery can very slowly discharge, even if this float voltage is well above its natural full charge open circuit resting voltage, which on a Northstar is 13.06 in my experience, My Dekas AGMs are about 12.84v.

By and large the smart chargers are given an efficacy rating by users reviewers, that they do not deserve, by those with little to no ability to actually make any judgements as to performance/ efficacy of the charger.

Ideal lead acid battery recharging can be taken to ridiculous extremes. The deeper the battery is cycled, the more important the charging regimen becomes, and the 95% charged battery needing a top up, is far different than teh same battery cycled 6 nights a week to 50% range but only recharged to 95%, and then on day 6 tries for 100%, as on Day 6 it will take many many hours longer.

Not being familiar with your charger, I will guess that it is expecting the amperage it is feeding the battery at absorption voltage, is not tapering to low levels. A new healthy Northstar held at 14.7v, will have amperage eventually taper to 0.05 or less. When my Group 27 Northstar was obviously at near end of life, the amps would not taper to 0.4 @ 14.7, but would stop tapering, then start rising again as the battery started heating. At first the bottom bounce was 0.5 amps, and over 5 months it would only taper to 1.1 amps before amperage started rising again. Voltage was also falling lower and lower each engine start even when fully charged, and when it was falling to 7.73, it would actually stop cranking for a bit, then keep going at which point the engine would catch. This is bad for the starter.


If a smart charger was waiting for amps to taper to say 0.5, but the worn out, or perhaps sulfated ( from chronic undercharging) battery, but amps never tapered to this level, it might just say 75% and never go higher and even might just shut off.

Remember, the smart charger's job is ultimately, max profit. A huge part of that is to not overcharge a battery, which can be unsafe due to excessive offgassing or thermal runaway. It is much safer to undercharge a battery, and indeed truly fully charging a battery requires more than a simple one size fits enough algorithm. Easiest of all is a bright green light and extra special marketing, and hope the consumer does not have the ability to actually determine true full charge.

If you wanted to test the performance of your vehicle, you'd want to know 0 to 60 times, and similar.
Equate this to the battery's ability to maintain voltage when powering the starter. The cold cranking amp rating. Turn the key and the starter draws ~ 180 amps. A healthy battery will be able to maintain 11+ volts powering this for a few seconds. A weaker, nearer end of life battery will be falling below 9 volts powering this same load for the same duration.

If you wanted to test the remaining capacity of a battery, this can be equated to the size of the size of the gas tank of the vehicle.
When new, the gas tank might be able to hold 20 gallons giving one a 500 mile range on the interstate, but when the battery is older and sulfated the 'gas' tank will still look like it holds 20 gallons, but is actually partially filled with acquarium gravel( sulfated) , and only able to store 12 gallons, and the vehicle range is now only ~ 280 miles all factors being equal.

So in order to check ones 0 to 60 times( remaining CCA), measure how much voltage the battery is able to maintain when starting the cold engine. Or use a carbon pile load tester.

To measure how far one can actually drive on a tankful, one needs to fill their tank, drive a steady speed and see how far it goes.

The 100 amp hour battery, when newish, healthy and fully charged, should be able to power a 5 amp load for 20 hours before the voltage falls to 10.5v, which is considered 100% discharged. It it can only power that 5 amp load for 10 hours before voltage falls to 10.5v the battery has only 50% of its original capacity remaining.
The battery at 50% capacity remaining, might still easily be able to start an engine, but the same battery being deeply cycled would likely not be able to stre enough energy to be used just as hard as it did when new. The 50% capacity battery in deep cycle usage would scream 'INADEQUATE!!" to the user watching their voltmeter during discharge, but the 50% battery as a starting battery likely still easily starts the engine, until it gets really cold out.



In general when capacity decreases to 80% of when new, the battery is recommended to be replaced as the risk of sudden failure after this point raises significantly.

when 100% discharged, the flooded lead acid or AGm lead acid battery will require no less than 102% of the energy removed from it, in order to be returned to 100%. As the battery ages this increases to 110%, then 115% and just gets worse and worse.

When recharging to full, one needs to be able to determine when full charge has occurred. With Flooded batteries with removable caps, a hydrometer dipped into the cells will show when specific gravity reaches previously established maximums, generally in the 1.275 range, but with an AGM, the ONLY way to be sure when full charge has been achieved, is by watching the amperage taper, when the battery is held at 14.4 to 14.8 volts. Lifeline states when held at 14.4v when a 100 amp hour battery can only accept 0.5 amps, it can be considered fully charged.

This is a good threshold, but perhaps on Odyssey or Northstar which are thin plate pure lead vs Lifelines much thicker plates, one should wait until it tapers to 0.2 amps per 100Ah of capacity instead. These TPPl agms will likely taper to less than 0.05 amps when new, but it could be unnecessarily abusive to get from perhaps 99.993% to 99.999%. The extra 0.007% can be achieved at float voltage, over 8+ additional hours.

Again, when an AGM battery is never really worked hard, and especially with these TPPL agms, when they do not get to stretch their legs/ lungs, they get all petulant. They are like an unexercised thoroughbred. Top charging is good ovbiously better than being kept at 80%, but really a petulant AGM needs its version of an italian tune up. Deplete it to 12.1v or less with a relatively large load, like the headlamps left on 10 to 15 amps) and measure how long this takes, then immediately feed it no less than 25 amps until it reaches 14.4 to 14.8v, then hold it at 14.4 to 14.8v until it tapers to the 0.3 amp range. Never discharge to less than 10.5v under lesser loads like headlamps, and never intentionally leave a discharged battery to sit in a well depleted state.

If ones plug in charging sources are well short of 25 amps, then the alternator can easily exceed this, but the voltgae regulation will likely back off from 14.4v and voltage being pressure, lesser pressure means less flow. I'd reccomend against idling to high amp recharge a well depleted battery, get on teh freeway, underhood airflow is important as is rpm above idle at keeping alternator from overheating.

If one really cant ever muster high amperage to recharge a well depleted AGM, The Lifeline link below on page 20 has a 'constant current' recommendation stage which is supposed to offset the degradation caused by deep cycling followed by less than a 0.2c charge rate, 20 amps per 100ah of capacity. They basically say apply 2 amps at the end of the 'normal' charge cycle for 2 hours and do not mention how high this 2 amps will push the voltage, but I will guess from experience it is well into the 16's.

please keep in mind Lifeline/Concorde AGM is the only AGm manufacturer which says anything about allowing voltages over 15.

charging a AGM from 50% to 100% is likely 6.5 hours minimum on a healthy battery, and 10+ hours on a mid life battery, and 13 hours or more on an end of life battery, before amps taper to the prescribed level when held at absorption voltage, which determines when the AGM can be considered full.



If you dropped off your Northstars, I'd hold them at 14.7v until amps taper to 0.3 amps, then use it hard over about 4 to 6 hours, until voltage fell to the 12.05 to 12.2v range with about a 6 to 10 amp load, which would have the battery somewhere in teh 50% charged range.
then I'd hook it up to my 100 amp power supply set to 14.7v.
I'd judge its condition by how much of that 100 amps it can accept, and how long it takes those 100 amps to raise voltage at battery terminals to 14.8v.
I'd also judge its condition by how long it takes amps to taper to 0.3.
I'd also hope that the amp hour counter on my charger output, when those amps taper to 0.3 at 14.7v, counted somewhere close to the original stated capacity.
I'd also run an IR thermal gun over each cell while charging and see if any one cell or bottom of a cell got significantly hotter than the other 5.

This particular deep cycle/high amp recharge/ amp hour counting method, if done back to back, tends to have the battery improve its capacity. I can and do go below the 50% state of charge boogeyman, and the longer the battery can accept higher amperage the more likely the heating caused by high rate charging helps to dissolve sulfation and improve CCA and overall capacity.

The marine guys have tested so called/ marketed pulse desulfating chargers, with no improvements in capacity noted.

The best performance restorative is a combination of the deep discharge/ relatively high amp recharge that gets the battery warm, followed by holding the battery at absorption voltage until either amps stop tapering, taper to a prescribed very low level, or start rising again.

Flooded batteries( and Lifeline AGM) can be equalized. This is an intentional forced overcharge, but ideally it is closely monitored and promptly terminated when specific gravity stops rising, or reaches previously established maximums, or the battery gets too hot, or starts heating rapidly.

EQ voltages on flooded batteries are generally 15.5 to 16.2 volts.

Lifeline's 'conditioning' procedure calls for 8 hours held at 15.5v, applied AFTER the battery has already been held at 14.2 to 14.4v until amps taper to 0.5 amps per 100Ah of capacity.

Odyssey's reconditioning procedure is here:

Lifeline's reconditioning procedure is on page 21, but read everything :


also if this topic is of interest and one wants even more info:

Performing an unneeded equalization/reconditioning procedure, is not just a waste of time and energy, but is likely detrimental to the battery. Such procedures performed on batteries primarily used as starting batteries which are kept at high states of charge/ no deep cycling, are likely of limited/ no benefit.

The TPPL agm needs to occasionally stretch their legs, compared to to a lower $$ AGm or flooded battery. I can baby my 420$ g31 Northstar and beat up My free Dekas, but the Northstar likes a good spanking. If I give the dekas a break, and cycle the grown lazy northstar, that first cycle, it is a petulant. Its voltage falls further and faster than it should, even though it was kept fully charged and floated at the correct voltage.

Take it to 11.9v over 6 hours and feed it 35 to 40 amps until 14.7v is reached( about 35 minutes) and hold 14.7 for about 6 to 7 hours, at which point amps have tapered to 0.4 or less, and the next deep cycle and subsequent cycles it is holding 0.15 to 0.25v more under the same load for the same duration.

I've cycled the snot out of my previous group 27 Northstar. Every time it started to noticeably underperform, the cure was ti intentionally discharge it to 11.9v or less, and then feed it no less than 35 amps until 14.7v was reached, then hold 14.7v until amps taper to 0.4v or less. Only the last 6 months it would not taper this low, and I'd terminate charging once they stopped tapering.

My Group 31 Northstar is not being worked nearly as hard as my previous 27 was, but it still responds extremely favorably after a significant depletion followed by a high amp recharge until amps taper to 0.5 or less. Simple topping up of it is not enough, its got to provide ~50% of its power over 6 to 10 hours, then immediately feed on 40+ amps, when I notice its performance is below that which I expect from it. It will take 40 amps for about 35 minutes before voltage climbs to 14.7v, at chich point amps start tapering. Once they taper to 0.5 or less, It performance is back. Again this is no less than 6.5 hours of charging, and but for that initial 35 minutes, is as fast as it can be charged.
 
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I've used this Optima® Digital 1200 Battery Charger for a few years and it has always seemed to work well. I did run a 4-hour "Repair Cycle" on the battery with the NOCO® Genius® PRO 25 (I just bought this charger.) and it completed "successfully." I guess I am going to have to start monitoring some technical internal aspects of the battery itself, but I am not all that technical. I do have a Foxwell BT-715 Battery Analyzer which I will have to learn how to use. I have no doubt that the battery is now "charged," the question is whether it is also desulfated? The Optima® Digital 1200 Battery Charger was telling me no and the NOCO® Genius® PRO 25 said yes. They could both be correct, but this is still confusing. Is the Optima® Digital 1200 Battery Charger really not useful? It was a well-rated battery charger. I called Optima® and they said they think the NorthStar battery is at fault.
Why don’t you just drive around and let the vehicle charge it.
 

jmegas

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Apr 25, 2017
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wrcsixeight,​


I've spent many hours reading over your long and extremely helpful response. You've obviously learned more about batteries than I will know in a lifetime. I think I have been seduced largely by advertising, which is what led me to buy the Optima® Digital 1200 Battery Chargers and the AGM NorthStar batteries. I know just enough to be dangerous. I live in Minnesota where the climate is awful and I drive very little, so everything is conspiring against my batteries. I am hoping to cure with equipment what I lack in your knowledge. I have a collection of at least ten battery charger/maintainers I have bought in the past ten years. Each year a company comes out with a new model which they claim has much smarter algorithms than their previous models and then I get suckered into buying a new model. Once I switched to AGM batteries I bought AGM-specific chargers, such as the Optima® Digital 1200 Battery Charger. I watched multiple Jim McIlvaine (of Optima now Clarios) YouTube videos where he talked about how wonderful the Optima charger was because it was designed specifically from the ground up to charge AGM batteries. (I also bought them from Summit Racing because I figured they would sell the best stuff. :-( ) As I say above, I guess I was seduced by the hype. Now I want to take the best care of my two NorthStar batteries (soon to buy a third) and I hope not to have to buy any more chargers--at least for a while. I just bought the NOCO Genius PRO 25 because I was sick and tired of waiting two days for my Optima 1200 to desulfate my truck battery. The NOCO tech support people seemed knowledgeable and patient and they assured me that their 25 amp charger would work much faster and more efficiently than my Optima 1200. They also had a "Repair Cycle" which only took four hours to run; far less than the 12 -16 hours I had been waiting for the Optima 1200 to get beyond 75%.

One point which you made has me thinking. The reason my NorthStar battery in the truck is taking longer to desulfate may really be because, even though it is only two years old, it may already be showing signs of wear. Perhaps that Optima charger is fully accurate, as you imply, but it is just having to work much harder to get the battery back to 100. If that is true, then my new 25 amp NOCO charger may only be masking the problem and not really "Repairing" the battery. It may be false reassurance. The NorthStar battery may already be showing signs of significant sulfation. Yes, it still works fine in the truck, but it's not a young puppy any longer. The "sensitive gauge" of my battery is the Stop/Start feature of my truck. Unless the battery is fully charged Stop/Start does not work. I am going to run some tests by doing some voltage and performance tests of the battery.

In the meanwhile, how do you recommend I care for the battery? Am I safe to charge it with the NOCO 25 amp charger, which works very quickly? Should I run the 4-hour repair cycle every time I charge it? Even *if* I run the 4-hour repair cycle, it *still* takes less time than it does with the Optima 1200 which can run for two days and *still* not move above 75%.
 
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If you have a bucket that is nearly full, dos it matter if you use a 1/2 inch hose with 30 PSI, or a 3/4 inch hose with 35 psi?

The 25 amp charger will only charge from well below 85% state of charge, to 85% charge faster.

I dont know what Noco or C teks 'repair' mode actually does.
I'd certainly not use them if they pushed voltage beyond 15v( unless very cold outside) on an agm.
if they simply hold their normal absorption voltage, for a few more hours, go for it.

YOur sparsely driven vehicles parasitic draw is far more a concern than self discharge of a TPPL agm, especially a cold one.
A cold AGM held on a maintenance charger, needs to have that float voltage at the correct value for the temperature. The battery temp sensor is a great thing which I think the 25 amp ctek has the option for.

I cant stress this enough, there is no point in putting charger after charger on battery Which is still at high state of charge, and expecting one or the other is going to do any restoration of capacity/performance.

The Northstar is rated at something like 800 deep cycles to 50% state of charge, assuming it is promptly and fully charged.
Do not think that draining it to 50%, is going to shorten its lifespan, as long as you truly fully charge it promptly.

I am saying you should intentionally deep cycle your northstar. Generally 'they' say not to regularly take a lead acid battery below 50% state of charge. But even if one does 100% discharges, the battery can likely do this 200 times, before its capacity falls to 80% of that when it was new.

Discharge it to 11.9ish volts under a 10 amp load. Knowing the load, and how long it was applied is useful, but more important is the voltage the battery rebounds to about 5 minutes after load is removed. generally 12.2v, rested, is considered 50% state of charge.

I'll go down as low as 11.2, then feed mine on a 40 amp or 100 amp adjustable voltage power supply, or sometimes put them in parallel if I can source two different 15 amp household circuits. (the 100 amp supply can only make 100 DC amps if it is fed 116vac or higher, and it basically maxes out a 15 amp household circuit and the voltage can fall to 109vac and it can only make 94 to 96 amps.

You have the 25 amp ctek, discharge the battery relatively quickly, in 6 to 10 hours until voltage falls to 11.9ish volts yet rebounds to near 12.2 volts in 5 minutes. then apply the Ctek 25 amp charger on agm 25 amp setting.

Once you do this, if you were to monitor voltage at the battery terminals, the 25 amps would likely instantly raise voltage to 12.8v, and climb towards the maximum Ctek allows for their agm setting. at 25 amps( it could fall short or exceed this!) it should take about a half hour to raise voltage to 14.4 to 14.7v.

Do note that there is often a little bit of weirdness as the battery wakes up. voltage might be seen to rise quickly to 14.4v, at a constant 25 amps, but then fall to 13.9 over 5 minutes, then slowly over 25 minutes climb back towards 14.4 to 14.7v.

From 50% charge it basically cant fully charge the battery in less than 6 hours and 6.5 hours is more likely for a healthy battery, and 8.5 hours for a mid life battery, and 10 to 12 hours for one in the last 20% of its useful life, except if that 'useful life' coincides with a Minnesota winter.

But one cant just wait for the green light. One needs to see how much amperage teh battery is accepting at absorption voltage. if it is a 100 amp hour group 31 battery, and it is being held at 14.7v, but quits charging while the battery is still accepting 1.5 amps, buess what, it is only about 95% charged. Finishing the charging at 13.6v float voltage from that point, will take no less than 12 more hours, and it is far better if the Northstar is held at 14.7v until amps taper to 0.5 and preferably 0.25 or so.

If amps do not taper to 0.5 but start rising above this level, it is not a good sign of battery health.

Get a clamp on DC ammeter. A 'good enough' one for battery charging is 35$ or so, make sure it says it can do DC current. Many in this price range can only do AC. place the meter next to a single wire set to dc amps, and press the zero button, then open clamp and place around wire, and it will display the amperage flowing from charger into battery. measure the voltage at the battery terminals. Multiply voltage times amperage to see total wattage the battery is accepting.

Would you drive without a speedometer/ odometer, and then try and figure out your mileage without knowing how fast and how far you travelled?

you can try, but it is much nicer to know how fast you are going and how far you travelled and also how much gas you consumed if you actually care about accuracy.

Knowing the amperage the battery is accepting at the voltage(electrical pressure) reaching battery terminals is kind of like knowing the speed, mileage, and amount of fuel consumed and then being able to determine if the vehicle is running as efficiently as it should.

I got so sick of so called smart chargers undercharging my batteries, I now just use an adjustable voltage power supply. It has a voltmeter, ammeter, amp hour counter attached on the DC output.. I dial it to the desired absorption voltage, say 14.7v, then hook it to the battery. If the battery was 50% or so, in about 6.5 hours it is accepting 0.5 amps.

If I cant be there to either shut it off at those 6.5 hours, then I just lower voltage to 13.6v, as obviously time to reach truly full is not important either. But often even after 12 hours at 13.6v, and I crank the pressure back upto 14.4, it can take a few hours for amperage to taper to that 0.5amp threshold which determines full.

So dont keep trying to top off a nearly fully charged battery of unknown health with charger after charger, drain it to ~ 50% state of charge, then hook the 25 amp charger up. Even if the charger prematurely ends the absorption voltage phase, the 25 amps has likely heated and softened and partially dissolved any potential sulfation on the plates. The farther you discharge the battery, the longer it can accept the maximum output of the charger, and the more the charging process can heat the sulfation, assisting it to redissolve into the electrolyte, increasing the amount of surface area on the plates for the chemical reaction to occur.

As said the Northstar can likely be 100% drained 200 times, as long as it is promptly truly fully recharged, so don't think an intentional deep cycle is somehow significantly compromising its life. These thoroughbreds TPPL agms enjoy working, as long as when they are done providing they are fed a lot, quickly, until full. AGMs can all too easily be tickled to death with too little charge current, especially the high $$ TPPL agms or the Lifeline/Concorde brand.

As far as the 30% limited charge rate cheaper AGMS, like Deka and most every other price competetive brand, well I have Dekas, and some smaller cheaper asian AGMS. I can and do feed them far over this 30% rate, just making sure they do not get too hot, and their voltage does not exceed 14.8v, and they all are exceeding my expectations of them. My 22 Ah one at 2 years of age, was able to start my 5.2 liter v8 by itself. the 3 year old 18 Ah one could when new, but not at 3 years.
If I drain the 18 or 22 amp hour asian AGMs to ~11.5 volts, and hook them to my 100 amp potential power supply which is set to 14.7v, they will accept a 65 amp spike but in a second taper to 35 amps, and this tapers to about 28 amps in a minute, and 28 amps tapers to about 15 amps in 18 minutes, and in another 15 minutes it is accepting about 6.6 amps, which is its 'maximum charge rate. The battery has increased in temperature by about 12 to 15f with this charge rate exceeding the max recommended rate by a factor of 5. Toilet paper, sure.......

So much of what one reads regarding the care and feeding of lead acid batteries on the internet is incorrect information passed down from Grandpa that gets a little more twisted and even further from reality with each retelling.

Do not be afraid to deep cycle your Northstar, do not be afraid to take it below 50% state of charge, and do not fear charging it at 25 amps. I'd say 25 amps is just barely enough. If battery was discharged down to 50% state of charge/ depth of discharge or so, and the 'smart' charger says it is fully charged in less than 6.5 hours, the charger is lying like a professional politician.

With the recondition/recovery button do anything? I dont know. If it holds absorption voltage for another few hours, then yes it should. If it is some pulse derived gobbledygook that is going to make the sulfate crystals sing and dissolve and magically restore the capacity, well thats what the professional politician would claim too.

If the reconditioning function brings the voltage of a 77f/25c battery above 15 volts, well the ONLY agm which says 15+ volts is on occassion acceptable, is Lifeline/Concorde.

But unless you have an ammeter, you will be driving without a speedometer/odometer, much less a fuel consumption meter and will just have to try and guess, and hope.

The dc clampmeter is an invaluable tool, and while it can also measure voltage, it is good to have a dedicated voltage so one does not have to switch the dial and pull out the leads.


This one samples voltage 5 times a second. So you can accurately see how low voltage falls when cranking your engine. If your Northstars are able to maintain 11 volts or higher on an overnight cold engine, after 2 years, it is unlikely you are going to need to use that 4 year free replacement warranty, especially if you do the occassional deep cycle with 25+ amps until truly full a few times a year. I do this no less than 80 times per year, and my previous northstar group 27 wound up doing it about 1200 times over 6 years.

You can expect voltage to fall lower and lower each engine start as the battery ages, or if it is undercharged, or the vehicle is super cold and has not started in a good long while. warm restarts are less useful as far a data collection as most warm fuel injected engines catch so quickly.

Each and every start can be considered a load test. A carbon pile load tester is basically imitating a starter motor, and its needle is showing how low the voltage falls, with green yellow and red indicating condition. The voltmeter sampling voltage 5 times a second can be watched each and every engine start. When it falls lower than one expects, has the battery been sitting, or inadvertently discharged or is it 15 degrees colder than usual?
if not perhaps an intentional deep cycle high amp recharge might cure that unexpectedly low reading.

While I have an amp hour counter and judge health by how much voltage the battery maintains powering x amount of load for x amount of time( usually 6 to 12 hours) , I also watch voltmeters every time my starter motor cranks, and every that time this voltage is less than I am hoping to see, and I know the battery is fully charged, and it is not significantly colder outside, then I know it is time for a deep cycle/ high amp recharge/true full recharge, and every time, but near the very end for my previous 6 year 1200 deep cycle norstar( may it rest in peace) , the battery performance is improved by the deep cycle/ high amp recharge charge to truly full treatment.

Find out what the amp hour rating of your specific battery is, divide that by 20, and try and find a 12vdc load which measures that much amperage. Sometimes it is easier to use a 12vdc to 120vac power inverter and dial in an ~ 5 amp load for a 100 amp hour battery, with various appliances around the house. A light or a fan, heating pad......

While a 10 hour capacity test at the 20 hour rate is far from ideal, if the 20 hour load applied for 10 hours has the battery voltage rebounds to 12.2ish 5 minutes after load is removed, one can say with some degree of confidence the battery still has 100 amp hours of capacity.

If one gets a new battery, fully charges it, and sees that the voltage on a 32 degree morning start stays at 11.97, then that is an excellent benchmark for judging each and every 32f cold start for the life of the battery, and being surprised with a failed no can do battery would be extraordinarily unlikely.

So you can judge battery health not only by how much voltage it maintains powering a large load for a short while, but also a smaller load for a lot longer.

Also you can judge the battery health by how much it is able to accept from a high current charging source, and how long it takes before amperage tapers to the prescribed full level when held at absorption voltage. But the key is knowing the amperage, and being able to hold absorption voltage unitl the amperage tapers that far, which is something which becomes a lesson in futility with most so called smart chargers, as they all seem afraid to complete the task for fear of overcharging and lawyers, and besides most of the public just needs to see a green light anyway.

An in reality, batteries are rented, as they are all doomed to fail. it can be cheaper and easier to just replace as needed rather than trying to become a lead acid battery whisperer with all the tools and time required to figure out the battery's remaining ability, and guess at its remaining longevity.

I use a lot of battery power, and having constantly prematurely failing batteries was why I spent so much time and effort figuring it all out, through experience and insatiable curiosity. I use far more electricity and get far more cycles/ KWH per $ than when I just replaced as needed.

I should go lithium, but not until I wear out my existing AGMS, and they are nowhere near there at this point.
 
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...When I spoke to an odyssey engineer a while back he was adamant that if the long term float voltage applied from a float or maintenance charger was not 13.6v, at 77f, then it should not be floated long term. Lots of so called 'maintenance' charger will float at 13.2, even on the AGM setting.....
The $217 8-amp charger from Battery Minder is guilty of undercharging during float when using its dedicated Odyssey setting. It floats at 13.2V @77F. I owned one for a short time, but returned it.

 

jmegas

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@wrcsixeight,​

Once again, it takes me many hours only partially to digest your helpful response. I thought I alone had caught the "battery bug," but you appear to be afflicted as well. :-( I also need to clarify a few things. I *only* have the Optima 1200 and NOCO Genius PRO 25 as my *latest* generation chargers; I do not own the 25 amp CTEK PRO25S and I cannot speak to how it works. I do know that the NOCO Genius PRO 25 has a four-hour repair cycle and I know that my Optima 1200 seems to hang forever at 75%. I also am taking careful notes on what you are saying and I want to make certain I get some things correct. You say that AGM batteries should have 14.8v charging / 13.6 v floating and FLA batteries should be 13.6v charging / 13.2v floating. Do I have those numbers correct? I especially wasn't certain on the FLA batteries; although I don't any longer own any of them. (I have become an all AGM shop.)

Also, you said in your first response. "The lead acid battery lives it longest life when it is truly fully charged and kept cool." By charging my batteries all the time I am only trying to make certain they are always fully charged. (I don't much have to worry about keeping them cool here in Minnesota. :)) I have two cars and I don't drive either of them very much. Both have two year old NorthStar AGM batteries. I keep one on a smart Optima 1200 charger 100% of the time. The other I only charge once each week because it sits outside and I don't want somebody stealing my charger. I do not drive enough to keep it fully charged merely from driving it and I don't want to stress the alternator.

I am going to have to learn how to measure the current state of my battery more thoroughly; but, fortunately I currently do have most of the equipment you mention. For one, I have a Foxwell BT-715 battery tester which was designed to test many of these battery characteristics. I also have Fluke multimeters; but, unfortunately, I haven't learned how to use them yet.

I do need to maintain the truck battery which I keep outside. I assume I should keep it, "fully charged and kept cool" as you said above. The only way I can make certain it is fully charged is to use a battery charger on it. Because I am totally frustrated with the Optima 1200 charger hanging at 75% for days at a time, I am inclined to switch to the NOCO Genius PRO 25 where I can quickly charge the battery. I realize that is not doing as good a job; but, in a way I am getting tired of caring. (I am also bothered immensely that the battery I keep in the garage on the Optima 1200 charger reads 100% ,whereas I can't seem to do anything correct to get the truck battery outside to budge from 75%.) Lastly, I am coming into the driving season for my truck when I will drive it several thousand miles over the next few months. Mostly I just want to keep the Stop/Start working most of the time, *if* I can. I am also getting tired of having to know this much about batteries!!!

I would be a very happy camper indeed if I could somehow restore my truck battery to the point where the Optima 1200 charger would return it to full functioning in 12 hours or less. Perhaps that will happen after my next 1,000 mile trip.

I also enjoyed your comment on batteries only being "rented." It seems like much of the "stuff" in our lives is only "rented" today. For years I have had a document on my computer regarding "Obsolete Electronic Equipment," It seems that almost everything today has an ephemeral life cycle. It works for a while and then it is replaced by something newer, better, and faster. Fortunately batteries, even AGMs, are inexpensive enough that they can be replaced. :)
 
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Flooded battery float is usually in the 13.2v range, absorption voltage anywhere between 14.4 and 14.9. I could find and post links, but I wont, showing various deep cycle flooded batteries recommending these voltages with very wide ranges. All of them are for a 77f battery. Some say to add more or less voltage for each rise of fall in temperature.

same with AGMs, I can find, but wont, float recommendations anywhere from 13.2 to 13.8v and absorption from 14.2 to 14.8v. again all at 77f or 25 c battery temperature.

The Northstar an ODyssey both recommend floating at 13.6v, and this is with a 77f battery .With a 30f battery, I don't feel like doing research for this or that specific batterys recommendation, or doing the math, but the ideal float voltage for a 32f battery Northstar or Odyssey is in the 13.8 to 13.9v range.

If float charger is holding a cold AGM battery that should be held at 13.9v, at 13.2 instead, well this is what the odyssey engineer specifically said to avoid, and it is why Sublgt seems to have returned his batteryminder, as it was too low.

I have noticed when I float my NS, or Deka intimidators at too low a voltage, the battery discharges.
i have noticed when battery temp drops, and I do not adjust voltage higher, the battery discharges.

any discharged battery is capable of sulfating.

The lower the battery discharges, the longer it sits discharged the more sulfates form to occlude the plates, and the longer it sits sulfated the physically harder the sulfation becomes, and situationally more difficult to redissolve into the electrolyte when recharging..

The best way of attempting to dissolve this sulfation, is not by putting magic stage 8 owner fellate extra special marekted 'smart' charger on it and press the magic button and hope to see 100 instead of 75,......... it is to intentionally discharge the battery to the 50% range, or a bit lower, and then high amp recharge it.

The higher amperage will force the electrolyte to migrate through glass matting deeper into plates, as well as heating the sulfate which might help dissolve it easier, opening up surface area on the plates, potentially restoring storage capacity and the ability to deliver high burst of amperage/maintaqin higher voltage when delivering that amperage.

The charge voltage needs to be held at 14.4 to 14.8 for as long as it takes for amperage to taper to 0.5 amps per 100 amp hours of (when new) battery capacity.

I'm not going to dig into the charge algorithm of the 1200 optimate or the Noco, I don't care about them, nor their claims of magical physics defying battery restoration, nor the thousands of raving fanboy ignorant reviews by those who have never used an ammeter, much less a voltmeter, and tried to gauge how much electricity the battery has delivered, or accepted.

If they are all the charger you have to work with,. the best thing I can recommend, is to discharge the battery over 6 to 10 hours to the 50% range, which is ~ 12.2v, ~ 5 minutes after the discharging load was removed. Then set it to the agm setting, on 25 amp setting and wait until it says its done. Then laugh at this obvious lie, then load battery again until battery voltage falls below 12.7 volts, then restart the charger on the next lowest amperage level, let it fire up, then turn off load.

lather rinse repeat.

You want to hold absorrption voltage for as long as it takes for amperage at 14.4 to 14.8v( northstars current specs) to taper to 0.5 per 100 amp hours of capacity, or less. This might take 6 hours, it might take 12 hours. 6 means a healthy battery, 12 means it is not. Not having an ammeter means you are essentially blind, only that something might be happening, but you dont know what.

If you say used the headlamps to drain the battery to 12.2v/50%, and if you measured this took 4.25 hours, if you were to do the same discharge again after the discharge to 50%/ charge lather rinse repeat, you might find it now takes 4.75 hours to drain the battery to 50%, indicating the battery did regain some capacity.

if you just restart charger A or B over and over again without discharging it to the 50% range, and hope the charger is magically restoring capacity.............

If all you are doing is putting your faith in a number spit out by a smart charger, 75, and thinking the battery is indeed only 75% charged, then I cant help you.

Restoring lost capacity can take a lot of effort and potentially yield no results, but whats the point in trying if you have no idea how to quantify any potential results, other than if some smart charger says 100 instead of 75, which means just about next to nothing, unless supported by some other data.

I have never bothered acquiring an impedence tester tester, though I would find the Ohm reading an interesting data point to watch as the battery ages.

Most every new battery will far exceed the CCA rating one programs into their impedence tester.

Basically they determine 'state of health' by the percentage of CCA it thinks the battery still has, compared to what it is rated at, and basically every charger out there determines % of charge by the voltage when the battery was first hooked to the charger. Yet voltage is a poor indicator of state of charge comparing battery to battery, as my Northstar full charge open circuit rested voltage is 13.06v, my dekas are 12.84v, and I've had flooded batteries that were only 12.68v. The charger or impedence tester might see 12.72 volts and declare 97% charged, but if it were on my Northstar, 12.72v open circuit rested is more like 75% state of charge.

One can also likely influence the Ohm reading of an impedence tester, therefore the CCA reading it spits out, by changing the position and pressure the clamps exert on the battery posts.

A smart charger, or impedence tester are not magical battery whisperers. the best possible lead acid battery charging is done with an adjustable voltage power supply and a human with the desire to watch a voltmeter and an ammeter and hold the battery at a high temperature compensated absorption voltage for as long as it takes for amperage to taper to prescribed levels.

Improvements might be possible it the battery is discharged significantly, then immediately recharged at a higher rate than one would normally apply. It is likely the most effective way of potentially restoring lost capacity.

If one has only a smart charger, and believes that the smart charger is performing magical capacity tests, and is capable of not only truly fully charging in a physics defying timespan, but then also has a the extra special setting capable of performing magical restoration of lost capacity or lost cranking amps, at the press of a button, well there is this bridge for sale somewhere i can sell you, and I promise your favorite professional politician will be there to shake your hand, and tell you how smart you are too.
The best you can do with what you have is just discharge the battery to ~ 50% , and use the 25 amp charger. When it stops and flashes the green light, load the battery again, restart the charger. then turn off the load.
lather
rinse
repeat
hope.

it might help
it might not.

But without an ammeter, you will never know, and have no chance of knowing, or much of a chance of learning.

You seem hung up on the 75% number some charger is displaying, yet have no idea what the charger is actually trying to deliver to the battery.

I can only guess what the charger might be seeing, might be thiking, but one thing i am sure of is that the battery is neither at 75% state of health nor 75% state of health, and if it did actually correspond with 75%, well a broken analog clock is right twice a day too.

One thing to keep in mind as well, is that if one is charging the battery in the vehicle still connected to teh vehicle, the load on the system of a modern vehicle wwith doors open or hood open and dome lights or body control module computers on, these will place a load on teh charger, and the charger has no idea if this is going into the battery or going to power a load.

This is yet another reason why smart charger marketing is ridiculous, as the algorithm does not take into account that most are not going to disconnect the cables to the battery and charge it completely independently from any potential load applied by the vehicle.

Want to really screw with your smart charger, when it has reached absorption voltage, turn on the headlights for about 30 seconds, then shut them off. The smart charger will first try and maintain absorption voltage by increasing amperage delivered, and then when the load is removed the voltage will skyrocket well above 14.8v and the charger will likely stop and flash an error/ bad battery sign.

Is the battery bad? of course not. The charger just never expected that there would be a dc load on the charger other than the battery itself,

Another reason I use an adjustable voltage power supply, as I can turn a large DC load on or off and it just holds the voltage I choose with 40 or 100 amps of potential to maintain that voltage. It might move 0.03v up or down with load added or removed, but it does not shut off. I have an ammeter showing how much amperage the charger is making, and I have an ammeter showing how much amperage is entering or leaving the battery. Only when there is no DC load, do they read the same.
 
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One more thing to keep in mind, is while it takes a long time to truly fully recharge a battery, this time assumes the battery is ebing held at charging voltages well above float voltage.

many modern vehicles try and keep the battery at ~ 80% charged. The alternator is basically turned off by the voltage regulator, when it is mostadvantageous for MPGS, and then when braking it asks the alternator to make enough amperage to bring battery voltage to 14.8ish volts. if the battery were at 99%, then this only takes 0.5 additional amps or so, but the 80% charged battery might need 30 amps to be brought upto 14.8v.

Each 25 amps the ~ 55% effecient alternator has to produce, requires one engine HP, so the only way the alternator can be used to try adn squeeze aout marginal gains in fuel efficiency, is by keeping the battery at a low enough state of charge that when cranking the pressure/voltage up, when braking or coasting, it then might add 0.06mpg to the total.

So It is unwise in the extreme, to think that simply driving long distance is going to fully charge the battery. One would need to know the battery voltage the entire time, adn lots of modern vehicles will have voltage yoyo between 12.6 and 15 volts depending on when teh engine computer thinks it might be most advantageous for MPGS.

Basically this strategy sacrifices the battery longevity for minor potential gains in MPGS, and is likely a contributing factor why many mbattery manufacture warranties have been shortened.

Lots of people will take a voltage reading just after engine starting, see 14.4v, and assume that forever after that is the voltage held. Perhaps on pre 90's vehicles this might be true, but it is much less likely on anything modern.

There's not much one can do when one's vehicle voltage regulator decides to let battery discharge for mpg gains, other than to use a charger regularly to at least try and bring it to 100%, even if it is doomed to be allowed to be discharged by the MPG seeking voltage regulator to 80% State of charge the next time the vehicle is driven.

Most people attribute the sticker on the battery to its longevity, but the battery longevity is more influenced by average state of charge it is held at, and average temperature.

Different batteries might be more resilient to living chronically undercharged, but by and large 'this battery good, that battery bad' has no supporting data, and the manufacturer of the battery and who stickered it during the different reports of baty A or B, are no longer applicable.

Some vehicles with underhood batteries can really heatsoak their battery on engine shutdown. some others to much lesser degree. Huge influencing variable, often completely ignored.

My Underhood Northstar has a tight fitting radiant heat barrier, and is almost always surrounded by air that is within 2f of ambient. Tight fitting not to the battery, I left a 3/4" gap all around it for shedding heat from high amp recharging, but tight fitting against underhood hot air or radiant line of sight heating.
 
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....You say that AGM batteries should have 14.8v charging / 13.6 v floating and FLA batteries should be 13.6v charging / 13.2v floating. Do I have those numbers correct?

Don't your Northstar batteries have a sticker on top, with the recommended charge voltages?
 
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Idaho
...The Northstar an ODyssey both recommend floating at 13.6v, and this is with a 77f battery .With a 30f battery, I don't feel like doing research for this or that specific batterys recommendation, or doing the math, but the ideal float voltage for a 32f battery Northstar or Odyssey is in the 13.8 to 13.9v range.
In the Odyssey 2016 tech manual, the temperature compensation coefficient is +/-24mV per degC. At 0degC the compensation value is +0.6V and the temperature compensated float voltage would be 14.1V to 14.4V

In the Odyssey 2021 tech manual, the coefficient has been decreased to +/-18mV per degC, presumably because the latest generation "AGM2" battery has differences in materials.

Also in the 2021 manual is the statement: Regardless of temperature, the minimum charge [float] voltage is 13.2 volts as lower voltages will damage the battery grids and shorten battery life. A similar statement is also in the 2016 manual.

The 2021 manual:
The recent integration of ODYSSEY Battery and NorthStar Battery brought together years of intelligence and research and development, resulting in the creation of the next generation of AGM - TPPL batteries. AGM2 is a unique design of Valve Regulated Lead Acid (VRLA) batteries that combines three major technical advancements in one battery: super high-grade materials + refined chemical formula + Thin Plate Pure Lead (TPPL) technology. This sets AGM2 batteries apart in terms of power, fast-charge acceptance, shelf-life, durability and most of all exceptional value for your investment.
 
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jmegas

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wrcsixeigh,

Once again I have very much enjoyed your two long replies and I have spent hours trying to digest parts of them. I agree with SubLGT that you have more than enough excellent material for an eBook. You would be guaranteed at least two sales immediately. :)

I'm still confused about those voltages. I have written down from your statements that AGM batteries require 14.8v – 14.2v charging / 13.8 – 13.2v floating and FLA batteries should be 14.9v – 14.4v charging / 13.2v floating. It is my understanding, and you have made several statements to that effect, that AGM batteries require *higher* charging voltages than FLA batteries. Therefore, I am confused with the numbers you provided? Even my NOCO Genius PRO 25 manual says AGM batteries *require* higher charging voltages than do FLA batteries.

You make an *excellent* point regarding my taking the 75% of my Optima 1200 far too seriously, and I appreciate that point. I'm assuming it means the battery is badly sulfated but I need to measure that some other way. Today was my "battery charging" day for the truck. I used only the NOCO charger and it completed the charge in approximately 15 minutes. I assume it did not desulfate the battery; but, at least, the battery does have a charge of as much as it can currently hold. I am going to have to run some of those stress tests you mention to determine the actual condition of the battery. That is a project for next week. I'm also reading about some of the tools you mentioned, many of which I was previously unaware.

I also knew *none* of the information you provided regarding the voltage regulator turning off the alternator to conserve fuel. That makes perfect sense. I did know that one should *not* use their alternator to charge their battery, but this shows why it is so ineffective. We once drove 375 miles to our cabin and the Stop/Start feature never started to work until we arrived. It took 375 miles of driving to charge the battery!

As for the warranties on batteries getting shorter, I had heard a different explanation. With cars having more and more parasitic draw, and standard cars requiring higher and higher operating voltages, it places far more demands upon the battery. Flooded lead acid technology hasn't changed much. In fact, this is what encouraged me to migrate to AGM batteries in the first place. I was having to replace my truck battery every two years. (Same non-use problem, but a different truck.) From what I had read, AGM batteries would better tolerate the specific type of abuse I gave batteries. From some of your comments, however, I am beginning to think that AGM batteries are not the panacea I thought they were. *No* type of battery likes to be abused! My AGM that is in the garage and *always* on an Optima 1200 charger is doing great. The one outside in the truck which is only charged once per week is starting to show serious signs of wear. As I said above, I will have to do more serious investigations with actual data, but perhaps I can't expect *any* battery, even an expensive NorthStar AGM, to withstand this type of abuse.
 
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