Shelf life of AGM battery

blupupher

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When I bought my '94 Goldwing in June of this year, the owner also gave me a new Deka ETX18L AGM battery still in box.
I do not see any decipherable date code on the battery or box (there is a "C4" sticker on the side of it so maybe March 2014, and there are some letters and numbers etched into it, but no idea what it means).
The AGM battery on the bike has a 2016 date written on it in a sharpie (no sticker), so guessing that was when it was installed, and it still works just fine (and is plugged into a trickle charger if not ridden for a few days).

Right after I bought the bike I put the new battery on a 2 amp charge overnight. The next morning, it was fully charged, and I stuck it up on the shelf.
I don't remember if I checked the voltage before charging, but today I checked it and it is at 11.84v after sitting for 3 months.

I know AGM are different than flooded, but not sure how to store it. Reading online has not really helped, most talk about winter storage (and even those conflict), not long term.
Should I just let it sit on the shelf in the garage till needed, then give it a good charge and start using?
Should I charge it periodically when I think about it (every few months)?
Should I leave it on a trickle charger (I have a spare one that is good for AGM batteries) till I need it?
It could be a month, or could be years till needed.

Or should I sell it now and just buy another one when needed?
 
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C4 would be early 2014 yes. You should leave it on a battery maintainer and at some point test it but after 6+ years it's probably trash.
 
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Well maintained AGM batteries only lose 1-3 percent capacity/charge per month vs a flooded battery which loses 6-12 percent capacity/charge per month left uncharged.

If the battery is 6+ years old and was not well maintained before you got it... It likely is a goner.

Though like cr94 said... try charging it and see if it holds a charge. Worth a shot.
 

JHZR2

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In float storage at cool temperatures, they can last up to 20 years.

But sitting anywhere below 100% results in irreversible (at least somewhat) sulfation and thus capacity loss and impedance growth. So it is in a poorer shape than it was. If you want to keep it, great, but keep a proper float/maintenance charger on it.
 
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Googling the battery, Amazon says it weighs 18,040 pounds.

Moving on, different source:
The Deka replacement battery ETX18L Battery Specifications:

  • Voltage: 12 Volt
  • CCA: 340
  • Capacity: 20 AH
  • Chemistry: AGM
  • Length: 8.13"
  • Width: 3.56"
  • Height: 6.38"
  • Weight: 15.5 Lbs

Ok a 15.5LB 20 amp hour battery with 340 CCA is a battery built for high CCA. Thinner porous plates and likely high specific gravity. High specific gravity of the electrolyte means more aggressive sulfuric acid, and an overall shorter shelf life, especially if stored in a warm spot.

I have similar size/weight AGM batteries, but Chinese AGMS @ 18 and 22AH capacity, the UB 12180 and Ub12220, 11.1 and 14Lbs respectively.

No CCA figures but I expect the 12180 has about 170 and the 12220 about 210. Either of these batteries, on their own, can start my overnight cold 5.2 liter V8, the 12180 just barely though.

While these two batteries say 5.4 and 6.6 amps max charging rate, I usually double that rate, and they when well depleted, they can accept 5x that amperage, and I will let them, for a few minutes.

If You were to give me your battery and say do your thing, After taking initial voltage, I'd attach it to a 40 amp power supply set for 14.7v, see how much amperage it takes for how long, and when it tapers to 0.1 amps I would remove charger, and watch voltage drop over a few hours, see where it levels off, and note how quickly it does so.

Then I'd likely drain the battery fully, using an old sealed beam headlight, about a 5 to 6 amps load, see how long it takes for voltage to hit 10.7v.

Then I'd attach it to my 40 amp power supply set to 14.5v. See how long it takes 40 amps to bring it to 14.5v, then watch amperage taper towards 0.1 while held at 14.5v. If any charging battery's temperature started approaching 100f, I'd reduce voltage sought by the charger, which lowers the amperage, 110f Max is what i will allow, 120f is danger zone. My charger has a meter attached counts amp hours delivered. Note how many it counts, how long it took.

Once amperage in the 14.2v range tapers to 0.1 amps I'd drop it to 13.6v and let it go for 12 more hours.

At this point I could run the same sealed beam light, and see how long it takes for voltage to hit 10.7v, compare to initial test.

Technically a new fully charged 20 amp hour battery can provide 1 amp of current for 20 hours before it is fully discharged.
This does not mean the battery can provide 5 amps for 4 hours though, or 20 amps for one hour.

Peukert effect says the bigger the load the less overall capacity the battery has to give.

A sealed beam light will start about 4.5 to 5 amps at 12.8v, and amperage will decrease as battery voltage decreases.

Batteries love being fully charged, but in my experience AGMS held at float voltage forever, get lazy. I believe it to be good to exercise them once in a while, do not overdischarge them, do not slowly discharge them dead, do it relatively quickly, over no more than 20 hours., and do not fear high amp charging of AGM's, just be wary of their heat gain, and once it starts, it accelerates, and over 120f is the danger zone one needs to avoid.

An old sulfated depleted battery will require lesser amperage for lesser duration to achieve high voltages( mid 14's)
A new healthy deplketed battery will accept much higher amperages for longer before voltage rises to the mid 14s at the battery terminals.

Both, if discharged to under 12 volts cannot be fully charged in less than 5.5 hours and the sulfated one is likley 2 to 3 times as long, assuming the charger is seeking mid 14's and has ampple amperage available to raise battery voltage to mid 14's in less than an hour.

This amperage accepted and the duration until it hit absorption voltage, is very revealing as to its condition.

Seeing how much it accepts for how long, is one data point in figuring out the health of the battery.
repeating the same test, after discharging it, gives one the ability to compare to see if some capacity has been restored by a proper full recharge with battery heating high initial amperages. voltage limited to mid 14's.

Same with the discharge, a sealed beam discharging it to 10.7v, is a LOAD test, comparable to itself. How long can it power it before voltage drops to the same level as before?

Every time I am given older AGM batteries to restore This is my recipe. Some of them gain 20 to 30% on the initial charge and another 10 on the second. Some of them are so obviously compromised it is obviously not worth the effort to try and restore them by cycling them deep and high amp recharging. Sometimes I am not sure and try anyway, and sometimes the battery actually surprises me and other times the battery jumps off the cliff, as the actual load test and recharging are a bit abusive to it.

Since the battery in question has a very high CCA for its weight, I'd not stress hitting it with 40 amps when well depleted.

Odyssey AGM are a thin plate pure lead design, and have very high CCA ratings.

Their reconditioning process:




Any charging source applied will be better than no charging source applied, but some maintainers/smart chargers will not be able to ever fully charge an older questionable battery even if a smaller AGM.

Waking up an older lead acid battery that's been sitting or mistreated, takes more than just a maintainer.
Don't fear recharging AGM's at higher amperages, the regular low and slow trickle charge them mentality, can tickle them to death, and if they are already at relatively high state of charge, they can't be high amp recharged, and mush be discharged some first. Generally 12.2v rested, is 50% state of charge/ depth of discharge, and generally lead acid batteries should not be drawn below this level. If going below this level it is paramount to quickly recharge them and then recharge them to a true full, certainly not just 85% - 92%, like many smart chargers will do.

The charging sources available to you are likely highly limiting factors. Some smart chargers are not so smar, despite their marketing and well know brand recognition and vociferous fanboys, yet usually quit well before the battery is fully charged. The green light only means it has stopped holding the battery at absorption voltage, and is now holding float voltage.

Some smart Schumachers can goto way too high a voltages sometimes , even on the AGM setting which should never go above 14.8v. Other times they quit prematurely. Baby sit these.

Self discharge of any given battery has a lot of influencing variables, but heat is always the biggest, followed by state of health, and state of charge of the battery when left to self discharge.

While 2 to 3% self discharge per month is a good Average for an AGM, it really depends on teh brand and its condition. Lifeline NOrthstar and Odyssey can be under 1% per month as 77f when new and healthy. Some other AGMS can be 5 to 7%..

Lifeline Northstar and Odyssey are basically double the price of most AGM starter batteries sold, to the general motoring public, and overkill for 99.99% of them.
 

blupupher

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@wrcsixeight, wow, way more info than I planned on, thanks.

I think I knew the answer (this battery is probably not good), but wanted to ask.

I will probably put it on my regular charger (a Schumacher SF-1275A) @ 12 amps for a day or so, then set it to 2 amps for a few days, then let it sit for a few more, then see how it tests. If it does not hold a charge, I will get rid of it.
The GL1500 is a very picky bike about power and wants all it can get, so an even slightly bad battery will not work.
BTW, anyone know if places like Advance Auto or Auto Zone will give you core value for motorcycle batteries?
But then again, maybe I can just play with this battery for an "emergency" battery for a light or something?
 
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I have a very similar looking schumacher charger, but 2 amp and 10 amp settings, no 75amp temporary option.
On the 2 amp setting it maxes out at 0.68 amps and the 10 amp settings is about 4.6 amps.

If 0.68 amps can push voltage way over 14.8v, then no good. It just keeps going, pushing 0.68 amps and battery voltage can keep rising.

Same with the 10 amp setting, 4.6 amps is enough to push a battery well into the 17v range, where No AGM should be pushed.

YOur model claims to be fully automatic, mine does not, Automatic, implies voltage regulation. which should limit voltage to sub 15v levels, but schumachers are famous for going too high.

Use your charger, but if voltage exceeds 14.7v, terminate charging. If battery heats excessively, terminate charging.

4.6 amps, if your 12 amp setting is similarly deficient , hardly qualifies as high amp charging which can perhaps desulfate a lazy stored AGM, but you are going to have to discharge the battery some before it can accept higher amperage, and this exercising of the shelfed battery, can reveal its health and potentially improve its capacity.

AGM batteries without the CCA remaining to be used as a vehicle starting battery, can be retasked to power other smaller loads.

I've got one on my workshop floor with a 100 watt solar panel on it. Basically powers DC lights and fans and USB ports and a stereo all day long and can do the same for a few hours after sundown. Takes some tiny load off the grid and over a month billing cycle, a few KWH from the electric bill.

Eventually the battery capacity declines to near useless levels, but it still acts like a buffer in between solar charge controller and fans/lights. I put the temp sensor on the battery lid, and put it on the gel setting to lower max allowed charging voltage as old batteries like to heat up when charging all day long, even at low rates.
 

blupupher

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Just went and checked it, it is sitting between 13.9v and 14.2v for the most part, with the highest being 14.4v (this is on 12 amp charge after about 1.5 hours on the charger). Highest temp on battery via IR thermometer is 89°F (ambient is ~ 80°F).

On another side note, I have another AGM battery (a MotoBatt MB16a) that I know is not good for starting (pulled about a year ago and has been sitting on the shelf since then).
Not sure how "dead" it is (can use the info here to check), but if the ETX18L is "bad", could I charge/use them in together with a Battery Tender Jr (their website says it can). It would give me a theoretical 39 Ah rating (I know it would be less, but more than just a single battery).
I have been looking at getting a battery backup to power my CPAP, and this could be a neat little project to try to make one.
 
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Voltage is electrical pressure.
How much amperage is flowing at that pressure?
If its still 12 amps, the charger's limit, then the battery is likely still well less than 70% charged

If it is down in the 1.5 amp range it is in the rage of 85 to 90% charged.

It can take 12 hours holding the battery at 14.2 for amps to taper to 0.1 amps. Or they might never taper that low and instead start rising again.

Dont want amps to start rising again, even if battery is known lesss than fully charged. Remove charger, try again 12+ hours later.

An Ammeter is really a great tool to judge battery health, when charging.

I use something like this' wattmeter on my chargers to see whats is going on, as voltage alone tells only a tiny part of the story and can be very misleading.


There are many different clones of this style wattmeter, they are around 90% accurate in my experience, Some better than others, luck of the draw as far as i can determine. These make it easy to see what any given charger is trying to do..

Not knowing amperage flowing at voltage when charging is a bit like saying I need to drive from A to B, but I am not really sure where A is, or B for that matter, their distance apart, or in what direction. So I'll just start driving and the green light will let me know when I arrive..

Some are OK with that.

When you take voltage readings, put the test leads on teh battery terminals themselves, and then see if forcing more pressure on the alligator clamps, to dig in harder, changes that voltage. See if there is point source heating on the clamp's steel jaws with your IR gun.

The voltage should not be varying between 13.9 and 14.2, but continue to rise from one to the other as the battery charges.

12 amps applied should raise voltage over a period of time from 11.X upto 14.2+. The more amperage the charger supplies, the faster voltage rises. The more charged the battery, the faster voltage rises, the more sulfated the battery the faster voltage rises.

A well depleted battery accepting 12 amps and still well below mid 14's is a pretty good sign.

Don't know amperage flow, then you don;t know where A or B is and don't know how fast you are driving either.

Obviously becoming a battery whisperer is of limited value, unless you live on battery power and hate waste.
 
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the fact that that battery sat on the shelf filled for that long tells me its not going to be much good.
my 99 will reliably start on 2 revolutions and i find the cheap walmart type dry charged are no good past 2 seasons no matter how good you care for them.i suspect the cheaper batts run a very high sg acid to make up for lack of active material.
you certainly can attempt to somewhat desulphate the ones you have and make use of whatever life is left.
try holding them around 15v a few hours.
watch the temp.
i have used up to 16v on stubborn ones.
when the next destination is the core pile you can play.
i also notice some of these dry out and ir rises.
i have carefully opened many gel/agm and added small amounts of distilled water to each cell.
monitor ir and add in cycles till no more improvement is seen.
dont flood it get just to the point the separator isnt flat white.
i just did this to a deka 8d agm that was subjected to long term overcharge.
went from 38 mohm ir to 2.
about 2 oz/cell.
added to my 12v system.
gotta love free storage!
 
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wrcsixeight, how are you measuring capacity (Ah) in your batteries?


I use the wattmeter I linked above, or similar meters, on my charging sources and my loads. I see how much was amp hour and watt hours were removed, how many were returned in order to reach full charge, which is determined by the amperage accepted at absorption voltage(~14.5 to 14.7v) , and how low the voltage fell during those loads. On flooded batteries the temperature compensating hydrometer is the battery polygraph as to state of charge, with a couple caveats, like the full charged specific gravity of that particular battery needs to have been previously determined for comparison, among others

Performing an actual capacity test requires one apply 5 amps for 20 hours on a 100 amp hour battery.
The battery should be held precisely at 77f, the load should be precisely 5 amps as the battery discharges.

Obviously not easy to perform accurately.

My engine starting battery, I have a voltmeter whose ground and + voltage sense leads go right to the battery terminals. i watch to see how low voltage falls during starting each overnight cold start. When my previous battery degraded to less than 7.5 volts during starting is when I replaced it. When new and fully charged it would stay above 11.9v during the ~180 amp load.

There's all sorts of ways to guage battery capacity, state of health and state of charge and the more data and accumulated observations the better.
I don't have a capacitance tester, yet, to add to my arsenal. but these are of limited usefullness in terms of determining capacity of a deep cycling battery.


I judge battery health by voltage retained during a load, the amount of that load and their duration
I judge battery health by how much initial charging amperage it can accept when well depleted, for how long, the temp rise of the battery, and how long it takes for amperage to taper to the level considered full at absorption voltage. Not every recharge of course though.


Lead Acid Batteries that are more deeply cycled, age differently than those that are just engine starting batteries held at relatively high states of charge..

I've way more experience with the former, and the latter have surprised me how they behave, more than once.

Always eager for data, I get frustrated when someone makes claims to battery performance without any, other than it can still start an engine, or not.
 
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