I don't see how 12.4V could be 100% charged unless it was VERY cold.
Battery test results
- Thread starter parshisa
- Start date
I don't see how 12.4V could be 100% charged unless it was VERY cold.
Internal resistance, combined with the rated CCA
If you can get a 50% bigger battery for less than 50% more cost I'd do it. If it fits of course.
Why not a carbon pile load tester? Better method of testing but requires battery to be fully charged.
More CCA in same group size means thinner (weaker) plates. Avoid doing this. A larger group size is fine.
This is repeated often and it sounds right, but in reality, holds no water.
A old sulfated battery, above 90% state of charge, will indeed require more amperage to be held at 13.7 or 14.4v, than a new healthy battery, but it is no more than 0.5 to 1.2 amps more.
If depleted under ~ 80% State of Charge, the newer healthy battery will be accepting about double the amperage as the old sulfated ones at the same charging voltage, but at high states of charge, it will require less amperage than the sulfated battery, but the amount less is not significant, to the alternator.
A new healthy depleted battery can put far far more stress on an alternato, than an old depleted sulfated battery as it crequires far more amperage to be held at charging voltages.
An old sulfated unhealthy battery, at higher states of charge, does require more amperage to be held at charging voltages, but it is a small amount more.
It is not nearly enough to put significant stress on the charging system.
While it is often said the weak battery took out the charging system, it is far far more likely the failing charging system took out the battery, and was just diagnosed first. cause and effect reversed.
If one really needs to believe a failing battery takes out their alternator, then they should not plug in their cell phone to charge when driving, as the extra 0.5 amp load is going to overheat the alternator.
And driving at night with headlights on is to be strictly avoided, that~15 amps of additional load on the alternator, will surely push the alternator over the edge.
I don't have data on a battery with a shorted cell, specifically how much extra amperage a battery with a shorted cell requires to be held at charging voltages, but I will guess it is in the 10 to 20 amp range, and it is unlikely a battery with a shorted cell can still start the engine, though if the cell shorts from manufacturing defect early in the battery's life, the other 5 cells could still have enough Ooomph to start the engine, and in this unlikely case, the alternator will be making a constant 10 to 20 amps more than it otherwise would, compared to a healthy 6 cell battery.
Generally the cell shorts at nearer end of life, when all the cells are equally compromised and 5 compromised cells can't do the job without help, like jumper cables or Jump box.
The weak sulfated battery puts far more stress on the starter motor, than it does the charging system.
This old wives tale, of the weak battery taking out the charging system, needs to be locked up in a soundproof room with the old complaining biddies, as it holds no water.
If what you're saying is true, it's good news. But you're talking about old sulfated batteries at "90% charge". Most old, dying batteries are nowhere near 90% of charge. Mine was lucky if it was at 50% capacity. It cranked VERY slowly, and tested to only 333 CCA. Less than half it's rated capacity. That's going to demand a lot more than an extra 1.2 amps from the alternator.
A sulfated battery is like a Physically shrinking gas tank. When new it held 30 gallons, when sulfated it holds only 10 gallons. both can still be filled, but one holds much more fuel.
There is no potential for the '10 gallon' sulfated battery to ever hold 30 gallons again, and it can never accept the amperage a '30 gallon' battery can.
Capacity and cranking amps are different measures.
Capacity is more like how far the ev car can drive. the battery being measured in amp hours or watt hours, the distance in miles or KM.
Cranking amps is more like how fast it can accellerate. The higher the CCA, the more voltage it can maintain turning the starter motor, and the faster the starter motor turns.
both capacity and cranking amps decline with a sulfated battery, but dont confuse distance with accelleration.
A new 330 cca battery will not behave the same, during charging, or discharging, as an older sulfated 660 CCA battery( when new) that now reads 330 cca on some impedence tester.
And voltage is NOT like a gas tank fuel level indicator. Voltage is only accurate as to state of charge on a battery that has not seen any loads, or charging sources applied to it, for many many hours.
Surface charge voltage on a new healthy battery can remain artificially high for DAYS.
And a battery low on water, but still above the tops of the plates, and sometimes even with plates exposed, and fully charged, can also appear to be holding abnormally high full charge resting voltages, but fill it, and it will read lower and it will fall lower during engine cranking, even hot off the charger.
There is no potential for the '10 gallon' sulfated battery to ever hold 30 gallons again, and it can never accept the amperage a '30 gallon' battery can.
Capacity and cranking amps are different measures.
Capacity is more like how far the ev car can drive. the battery being measured in amp hours or watt hours, the distance in miles or KM.
Cranking amps is more like how fast it can accellerate. The higher the CCA, the more voltage it can maintain turning the starter motor, and the faster the starter motor turns.
both capacity and cranking amps decline with a sulfated battery, but dont confuse distance with accelleration.
A new 330 cca battery will not behave the same, during charging, or discharging, as an older sulfated 660 CCA battery( when new) that now reads 330 cca on some impedence tester.
And voltage is NOT like a gas tank fuel level indicator. Voltage is only accurate as to state of charge on a battery that has not seen any loads, or charging sources applied to it, for many many hours.
Surface charge voltage on a new healthy battery can remain artificially high for DAYS.
And a battery low on water, but still above the tops of the plates, and sometimes even with plates exposed, and fully charged, can also appear to be holding abnormally high full charge resting voltages, but fill it, and it will read lower and it will fall lower during engine cranking, even hot off the charger.
On the "Honda CR-V Owners Club forum" there are several threads about Honda putting too small of a battery in there vehicles, and also post about Honda reducing the load on alternators to improve MPG.
There are post about installing the battery tray from a 2013 Honda odysey to hold a larger group battery with more CCA. And also post that to make the charging system run at a higher voltae owners drive with the AC on or the headlights on.
There are post about installing the battery tray from a 2013 Honda odysey to hold a larger group battery with more CCA. And also post that to make the charging system run at a higher voltae owners drive with the AC on or the headlights on.
Engine displacement alone is not the only thing to consider when sizing what minimum CCA size battery an engine requires, because now days many engines are high compression, and that can require more CCA.
But starters these days have gear reduction drives and have an easier time turning over cold motors.
My SIlverado V8 uses a 1.1 kw starter motor.
And lets not forget that the CCA rating test is for thirty seconds, not the three that it takes a fuel injected car to fire up on the first crank.
Access to quantifiable data leads people to freak out, which is why oil pressure and water temperature gauges are either gone or deadened considerably compared to thirty years ago.
My SIlverado V8 uses a 1.1 kw starter motor.
And lets not forget that the CCA rating test is for thirty seconds, not the three that it takes a fuel injected car to fire up on the first crank.
Access to quantifiable data leads people to freak out, which is why oil pressure and water temperature gauges are either gone or deadened considerably compared to thirty years ago.
2.0 kW starter on my diesel... and it has glow plugs that take considerable current if it's cold enough to matter. Also, below 10V it's not guaranteed the ecu will even work. The common rail pump needs to build up enough fuel pressure and the engine RPM needs to reach a minimum threshold aswell. I need a healthy battery in my car for sure if it gets to 0F or below.
Thanks for this. You've taken a lot of worry off my mind. So.... Help me out here. Older vehicles from the 60's and 70's always had amp meters, that would tell you how much juice your charging system was putting out. Now a days they all have volt meters. Which is "better", and more useful?
My Jeep that I just put a new AGM battery in, shows 15 volts on the voltmeter when I'm driving. When it had the old crappy, dying 6 year old original battery in it, it showed 14 volts under the same circumstances. Only 1 volt difference. Yet it cranked VERY slowly. Now it spins like a top. So..... My voltmeter is pretty much useless, showing only 1 volt difference between an almost trashed battery, and a brand new one, once the vehicle was running and underway.
My 1991 F-150 that I just replaced the battery in, is just about the same. (The voltmeter in it is analog, where as in the Jeep it's digital). But it barely moved the needle with the new battery. What am I not seeing? Or is the voltmeter showing what the charging system is doing in relationship to the battery?
When my alternator went on my F-150 3 years ago, I knew something was wrong, because the voltmeter dropped WAY down. Even when I revved the engine. I put in a new alternator, and that swung the needle way over to the + side. Problem solved. I guess what I'm asking is, what the hell good is a voltmeter for anyway?
I always use the toilet flush analogy:
two similar unit, one half filled with brick: half the capacity.
open the water inlet valves, the water reaches the same level in both: same voltage
the one with bricks in discharges 1/2 the water before getting empty
From my own experience below 80% capacity the engine turns slower and longer before firing when it is cold but otherwise it can turn on even with much lower capacity but not reliably.
My motorbike starting becomes a problem unless the capacity is above 80%
two similar unit, one half filled with brick: half the capacity.
open the water inlet valves, the water reaches the same level in both: same voltage
the one with bricks in discharges 1/2 the water before getting empty
From my own experience below 80% capacity the engine turns slower and longer before firing when it is cold but otherwise it can turn on even with much lower capacity but not reliably.
My motorbike starting becomes a problem unless the capacity is above 80%
Over kill is for when the battery ages there will still be power to start the car.
Re read your post . The meter told you lots.
I like that brick in the toilet tank analogy. An increasing amount of coarse Aquarium gravel in a vehicle's fuel tank, is likely better than than my shrinking fuel tank analogy. I think it better represents how sulfation reduces the surface area of the plates where the chemical reaction occurs, and the amount the tank can hold.
Today's gauges are often dumbed down to keep the driver from freaking out when they notice something they are not used to seeing, and have no idea why that might be.
I'd not trust any stock dash voltmeter, unless one confirms it actually represents actual battery voltage. An accurate digital voltmeter in the 12v powerport/ciggy plug is better, but often this circuit is shared with other loads and those loads can drop the voltage it is reading below actual battery voltage measured at the battery terminals.
My 30+ year old vehicle came with an ammeter needle, no voltmeter.
When I did have an alternator failure, well before I knew much of anything about batteries and battery charging, 20 years ago, I did not notice that my ammeter needle swung the 1/16" of an inch from charging, to discharging. I only noticed something was wrong when my windshield wipers moved extra slowly, and my turn signal blinkers took extra long to blink on and off. It still started easily, and I carried a jump box for when it declined to the point it could not.
So in this case, I would have been much better off if there was a voltmeter showing 11.9v with engine running, rather than the 14.9 or 13.7 that the voltage regulator inside the ECM's internal vReg allowed, before alternator failure. The tiny 1/16" swing of the stock ammeter needle from charge to discharge, went unnoticed for as long as it took the 8 to 12 amp load( during daylight hours) to depleted my battery and cause windshield wipers to wipe significantly slower. The stock ammeter has been removed and replaced with a tachometer.
Engine starts themselves of a fuel injected engine really take extremely little of the battery's capacity, especially a warm engine.
My alternator failure incident way back when, was not easily resolved, as my knowledge of how it all works was so lacking. I had the option of a 90 or 120 amp alternator. Basically the Same price, so I went for 120 assuming I had the 90 which failed.
My battery was still heavily drained, but had enough to start my engine with the newly reman'd alternator installed.
Upon starting, the ammeter needle swung higher than I had ever seen before, for about 5 seconds, then fell back to discharging.
I did not realize the fusible link had blown. I then got experienced at alternator swapping, and then assumed the voltage regulator inside engine computer was at fault. I only had an ancient analog voltmeter, and no idea how to really use it for diagnostics.
Finally I took it to a sparky who found the blown link, and replaced the link. The fusible link was not blown visually. They are supposed to look blown and stretch out when pulled upon. Mine was not. The shop used 14 awg instead of the stock 10, I later found out, and that thing was getting ridiculously hot whenever my battery was depleted.
Now, as I use far more battery power, my charging system is refined. Dual alternators feeding separate battery banks. I bypassed voltage regulator inside engine computer, and control each alternator separately, manually, with external voltage regulators that I modified with external potentiometers on my dashboard, next to my 3 wire calibrate-able digital voltmeters, next to my Ammeters. 4 ammeters actually at this moment, two showing total alternator output, two showing what each battery bank is accepting, or delivering.
I recently removed the voltmeters i had on the Field wire going from voltage regulator to field terminal on alternators, as my curiosity was sated.
I also have temperature sensors thermo epoxied to alternator casing, and also to the voltage regulators backsides which act as heatsinks, to which I added finned aluminum heatsinks, and 60mm fans, as they were hitting 170F, quickly, at idle, with depleted batteries.
So voltage is basically pressure. The ammeters show how much amperage is flowing into, or out of the batteries at that pressure.
A depleted battery will accept much much more amperage when new and healthy, compared to when older and sulfated or just worn out, when its capacity is some fraction of what it was when new.
So voltage alone is not a great indicator of anything other than the electrical pressure. It says nothing about how much juice is actually flowing into or out of a battery, at that pressure. How much amperage is flowing at that voltage gives a great picture of the state of charge of the battery as well as the state of health, but the latter requires more experience watching how much amperage is flowing into that battery from different states of charge, as the battery ages., but when one sees that a known depleted battery is accepting low amperage at high voltage, it is a sign the battery's capacity is severely compromised.
If the battery is only ever used for engine starting, and never cycled deeper, then the ammeter would be much less revealing. as it would drop from about 70 amps immediately after starting and taper to less than 5 within a minute, and less than 1amp if it were 98%+ charged at the time of engine starting.
With an Ammeter reading total alternator output, One sees just how hard the alternator works to power the engine and all the DC accessory load whether headlights or blower motor, or fuel pump, ignition, electric windows, rear defroster, seat heaters, ect. The depleted battery can be considered a load, when the alternator can't make more amperage than the vehicle's DC loads requires at that rpm, and when it cannot, system voltage falls to or below battery voltage, at which point the battery provides the extra amperage, then with more engine rpm, and the more amperage that the alternator can make at higher rpm, the depleted battery then again becomes a load instead of a source.
When one can control the voltage, and has an ammeter, one can see how choosing 14.7v, vs 13.7v, basically doubles the amperage a depleted half life battery accepts, and triples the current a healthy new depleted battery accepts.
I basically choose 14.7v until battery bank A accepts less than 0.5 amps, then lower to 13.6v during the day or 13.8 to 13.9v at night as battery bank A is usually the engine starting battery, but I can choose either or, or even both.
On battery bank B ( the Dekas) I choose 14.39, but when amperage into batteries at 14.4v tapers to 5 or so I lower voltage to 13.4 or so, as that battery bank,( 6v golf cart AGM batteries in series for 12v) at that point, will accept about the same amount of amperage at either voltage.
Either battery, when well depleted bank can easily max out their individual alternators at idle, hot idle @ ~ 50 amps output, and if well depleted either can also max out their 120 amp alternators at 2K engine rpm too. The one alternator can slightly exceed its rating at 2300 engine rpm, the other one falls short of its rating and maxes out at ~ 1800 engine rpm.
Even with my vehicle's charging system, which is now refined for maximum rate recharging of depleted batteries, 80% to 100% state of charge takes no less than 3.5 hours. 3.5 hours represents the battery banks when they banks were new and healthier. The Deka bank now takes no less than 4.5 hours and the Northstar is right about 4 hours, and this is despite their age and cycle related loss of capacity.
80% to 100% taking so long, is where an adequate amount of solar wattage and sunlight, shine, as they have the time to complete the charging, silently, and the battery bank can then start its next discharge from 100% state of charge. When solar is inadequate i try and plug in and let my adjustable voltage power supplies hold absorption voltage till amperage tapers to the desired level, then I lower it to float, though I will often just lower to float if I will not be there when amps taper to the target level.
When a cycling battery starts its next discharge cycle, only having gotten to 90% state of charge, time after time, its ability to store and deliver energy, and then to also reaccept energy and recharge as fast as it could before, is compromised. The more partial state of charge cycles accumulated, the worse the battery performs, and the faster it degrades, and the harder it becomes to actually return it to its maximum potential remaining capacity, requiring higher absorption voltages held for much much longer before that benchmark is reached.
The lead acid battery always wants to be returned to a true 100% state of charge and kept cool. How much they dislike this 'less than ideal ' depends on just how much below 100% state of charge they average, as well as their temperature. Deep discharges are also very damaging to them, but more so when they are not returned to at least relatively high states of charge relatively quickly.
A parasitic drain drawing a Starting battery to 20% state of charge over 3 weeks is very hard on that battery. An Agm battery only slowly recharged from this point is especially temperamental as it really wants a significantly higher amperage rate to force migration of the electrolyte through the glass matting and deeper into the plates. The higher rates also heat the battery from within a bit more which helps dissolve that sulfation back into the electrolyte.
Lithium batteries do not mind partial state of charge cycling, but they cannot be safely recharged if they reach freezing temperatures, and most of the current Lifepo4 drop ins, their BMS's will not allow passing starter motor current, nor what the alternator could deliver to them if its output is not throttled back, way back.
Today's gauges are often dumbed down to keep the driver from freaking out when they notice something they are not used to seeing, and have no idea why that might be.
I'd not trust any stock dash voltmeter, unless one confirms it actually represents actual battery voltage. An accurate digital voltmeter in the 12v powerport/ciggy plug is better, but often this circuit is shared with other loads and those loads can drop the voltage it is reading below actual battery voltage measured at the battery terminals.
My 30+ year old vehicle came with an ammeter needle, no voltmeter.
When I did have an alternator failure, well before I knew much of anything about batteries and battery charging, 20 years ago, I did not notice that my ammeter needle swung the 1/16" of an inch from charging, to discharging. I only noticed something was wrong when my windshield wipers moved extra slowly, and my turn signal blinkers took extra long to blink on and off. It still started easily, and I carried a jump box for when it declined to the point it could not.
So in this case, I would have been much better off if there was a voltmeter showing 11.9v with engine running, rather than the 14.9 or 13.7 that the voltage regulator inside the ECM's internal vReg allowed, before alternator failure. The tiny 1/16" swing of the stock ammeter needle from charge to discharge, went unnoticed for as long as it took the 8 to 12 amp load( during daylight hours) to depleted my battery and cause windshield wipers to wipe significantly slower. The stock ammeter has been removed and replaced with a tachometer.
Engine starts themselves of a fuel injected engine really take extremely little of the battery's capacity, especially a warm engine.
My alternator failure incident way back when, was not easily resolved, as my knowledge of how it all works was so lacking. I had the option of a 90 or 120 amp alternator. Basically the Same price, so I went for 120 assuming I had the 90 which failed.
My battery was still heavily drained, but had enough to start my engine with the newly reman'd alternator installed.
Upon starting, the ammeter needle swung higher than I had ever seen before, for about 5 seconds, then fell back to discharging.
I did not realize the fusible link had blown. I then got experienced at alternator swapping, and then assumed the voltage regulator inside engine computer was at fault. I only had an ancient analog voltmeter, and no idea how to really use it for diagnostics.
Finally I took it to a sparky who found the blown link, and replaced the link. The fusible link was not blown visually. They are supposed to look blown and stretch out when pulled upon. Mine was not. The shop used 14 awg instead of the stock 10, I later found out, and that thing was getting ridiculously hot whenever my battery was depleted.
Now, as I use far more battery power, my charging system is refined. Dual alternators feeding separate battery banks. I bypassed voltage regulator inside engine computer, and control each alternator separately, manually, with external voltage regulators that I modified with external potentiometers on my dashboard, next to my 3 wire calibrate-able digital voltmeters, next to my Ammeters. 4 ammeters actually at this moment, two showing total alternator output, two showing what each battery bank is accepting, or delivering.
I recently removed the voltmeters i had on the Field wire going from voltage regulator to field terminal on alternators, as my curiosity was sated.
I also have temperature sensors thermo epoxied to alternator casing, and also to the voltage regulators backsides which act as heatsinks, to which I added finned aluminum heatsinks, and 60mm fans, as they were hitting 170F, quickly, at idle, with depleted batteries.
So voltage is basically pressure. The ammeters show how much amperage is flowing into, or out of the batteries at that pressure.
A depleted battery will accept much much more amperage when new and healthy, compared to when older and sulfated or just worn out, when its capacity is some fraction of what it was when new.
So voltage alone is not a great indicator of anything other than the electrical pressure. It says nothing about how much juice is actually flowing into or out of a battery, at that pressure. How much amperage is flowing at that voltage gives a great picture of the state of charge of the battery as well as the state of health, but the latter requires more experience watching how much amperage is flowing into that battery from different states of charge, as the battery ages., but when one sees that a known depleted battery is accepting low amperage at high voltage, it is a sign the battery's capacity is severely compromised.
If the battery is only ever used for engine starting, and never cycled deeper, then the ammeter would be much less revealing. as it would drop from about 70 amps immediately after starting and taper to less than 5 within a minute, and less than 1amp if it were 98%+ charged at the time of engine starting.
With an Ammeter reading total alternator output, One sees just how hard the alternator works to power the engine and all the DC accessory load whether headlights or blower motor, or fuel pump, ignition, electric windows, rear defroster, seat heaters, ect. The depleted battery can be considered a load, when the alternator can't make more amperage than the vehicle's DC loads requires at that rpm, and when it cannot, system voltage falls to or below battery voltage, at which point the battery provides the extra amperage, then with more engine rpm, and the more amperage that the alternator can make at higher rpm, the depleted battery then again becomes a load instead of a source.
When one can control the voltage, and has an ammeter, one can see how choosing 14.7v, vs 13.7v, basically doubles the amperage a depleted half life battery accepts, and triples the current a healthy new depleted battery accepts.
I basically choose 14.7v until battery bank A accepts less than 0.5 amps, then lower to 13.6v during the day or 13.8 to 13.9v at night as battery bank A is usually the engine starting battery, but I can choose either or, or even both.
On battery bank B ( the Dekas) I choose 14.39, but when amperage into batteries at 14.4v tapers to 5 or so I lower voltage to 13.4 or so, as that battery bank,( 6v golf cart AGM batteries in series for 12v) at that point, will accept about the same amount of amperage at either voltage.
Either battery, when well depleted bank can easily max out their individual alternators at idle, hot idle @ ~ 50 amps output, and if well depleted either can also max out their 120 amp alternators at 2K engine rpm too. The one alternator can slightly exceed its rating at 2300 engine rpm, the other one falls short of its rating and maxes out at ~ 1800 engine rpm.
Even with my vehicle's charging system, which is now refined for maximum rate recharging of depleted batteries, 80% to 100% state of charge takes no less than 3.5 hours. 3.5 hours represents the battery banks when they banks were new and healthier. The Deka bank now takes no less than 4.5 hours and the Northstar is right about 4 hours, and this is despite their age and cycle related loss of capacity.
80% to 100% taking so long, is where an adequate amount of solar wattage and sunlight, shine, as they have the time to complete the charging, silently, and the battery bank can then start its next discharge from 100% state of charge. When solar is inadequate i try and plug in and let my adjustable voltage power supplies hold absorption voltage till amperage tapers to the desired level, then I lower it to float, though I will often just lower to float if I will not be there when amps taper to the target level.
When a cycling battery starts its next discharge cycle, only having gotten to 90% state of charge, time after time, its ability to store and deliver energy, and then to also reaccept energy and recharge as fast as it could before, is compromised. The more partial state of charge cycles accumulated, the worse the battery performs, and the faster it degrades, and the harder it becomes to actually return it to its maximum potential remaining capacity, requiring higher absorption voltages held for much much longer before that benchmark is reached.
The lead acid battery always wants to be returned to a true 100% state of charge and kept cool. How much they dislike this 'less than ideal ' depends on just how much below 100% state of charge they average, as well as their temperature. Deep discharges are also very damaging to them, but more so when they are not returned to at least relatively high states of charge relatively quickly.
A parasitic drain drawing a Starting battery to 20% state of charge over 3 weeks is very hard on that battery. An Agm battery only slowly recharged from this point is especially temperamental as it really wants a significantly higher amperage rate to force migration of the electrolyte through the glass matting and deeper into the plates. The higher rates also heat the battery from within a bit more which helps dissolve that sulfation back into the electrolyte.
Lithium batteries do not mind partial state of charge cycling, but they cannot be safely recharged if they reach freezing temperatures, and most of the current Lifepo4 drop ins, their BMS's will not allow passing starter motor current, nor what the alternator could deliver to them if its output is not throttled back, way back.
Last edited:
wrcsixeight,
What is the ideal temperature for a lead acid, and AGM battery? And at what temperature does heat start to become a problem?..... Also, are you saying that AGM batteries are better served by being charged at a higher rate, than a comparable lead acid battery?
What is the ideal temperature for a lead acid, and AGM battery? And at what temperature does heat start to become a problem?..... Also, are you saying that AGM batteries are better served by being charged at a higher rate, than a comparable lead acid battery?