What is the maximum charging current for a 12 V 35 amp hour sealed lead acid battery if 5 of them are wired in parallel configuration? The battery states that maximum charging current is 15 A. But does that change since I’m wiring 5 of them together.
Max charging current
- Thread starter Radtech
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Looking at the MPP 1012 AIO inverter. From what I’m gathering and looking at the specs maximum current from the solar panels would be 40 A and maximum current from the utility would be 20 A for a 60 amp total if both charging at the same time. So I couldn’t go any higher than 60 A anyways but was wondering if I should even go lower. The default is set at 40A. But I can set it even lower 10A 20A or 30 A. Thoughts.
Typical max current that you can charge a flooded lead acid battery is around 0.15C and that is usually what the battery itself will accept. You could maybe try to force 15A into a 35AH battery by raising the voltage really high but you would risk boiling the battery.
Are these flooded,gell, or agm batteries?
AGM
But my confusion is why does the battery say max current charge 15A
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RCinFLA
Solar Wizard
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High charge rate for lead-acid battery creates a lot of electrolyte water electrolysis splitting into hydrogen and oxygen gas. On a sealed lead-acid battery, if internal gas pressure builds too high it will escape out the pressure relief vent port. When this happens you lose water from electrolyte that cannot be replaced.
You can charge a bit greater to 20-25% C(A) at low state of charge but only until battery reaches about 13.5v terminal voltage. This is where outgassing rate greatly increases. AGM's can take higher charge rate but should also be reduced above 13.5v. AGM's are electrolyte starved so they cannot afford to lose water from electrolyte.
Really high charge rate can eject lead from plates. For a flooded lead-acid the electrolyte will appear to have fine dark powder mixed into it.
15 A charge rate for a 35 AH lead acid battery will damage it.
You can charge a bit greater to 20-25% C(A) at low state of charge but only until battery reaches about 13.5v terminal voltage. This is where outgassing rate greatly increases. AGM's can take higher charge rate but should also be reduced above 13.5v. AGM's are electrolyte starved so they cannot afford to lose water from electrolyte.
Really high charge rate can eject lead from plates. For a flooded lead-acid the electrolyte will appear to have fine dark powder mixed into it.
15 A charge rate for a 35 AH lead acid battery will damage it.
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mikefitz
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Regardless of the actual charge current it takes at least 5 hours to fully charge an AGM battery from 50% to full.
An AGM battery will typically take 0.2C charge current and some manufactures state that ideally this should be a minimum.
My vote is 6 amps per 35Ah battery. 5 in parallel gives 30 amps as a maximum.
The manufacturer should specify charging volts, 14.4 to 14.8 charge. 13.5 to 13.8 float. Long term float should be lower 13.2 to 13.4.
Absorption time will depend of state of charge before charging and charge current available.
Ideally the absorption state should terminate when the charge current at full charge volts, falls to 1% of C, thats 1.7 amps for the 5x35Ah.
This will need at least 2 hours absorption time.
Mike
An AGM battery will typically take 0.2C charge current and some manufactures state that ideally this should be a minimum.
My vote is 6 amps per 35Ah battery. 5 in parallel gives 30 amps as a maximum.
The manufacturer should specify charging volts, 14.4 to 14.8 charge. 13.5 to 13.8 float. Long term float should be lower 13.2 to 13.4.
Absorption time will depend of state of charge before charging and charge current available.
Ideally the absorption state should terminate when the charge current at full charge volts, falls to 1% of C, thats 1.7 amps for the 5x35Ah.
This will need at least 2 hours absorption time.
Mike
So that is an AGM battery that will accept a bit more because of its lower internal resistance. The reality on those is that you won't get much more than 0.25C. I would not be raising the charge voltage to try to get them to 15 as you will shorten the life of the battery.
That vendor deals with consumers and consumer devices. Consumer get confused when you tell them that for most recycled-lead agm's (which these are, unlike pure-lead), the maximum current is typically between 0.25 to 0.3C.
Which for a 35ah agm, a max of 10.5A at 0.3C.
But why the 15A max rating? This is simply to try and accomodate consumers and extend the *possible* range of chargers they buy off the shelf.
What will happen in the real world, is that even tough 15A is too high on paper, because nearly ALL modern consumer chargers are of the cc/cv type, the cv will be reached quicker than normal, and the battery will be in the cv mode (the so-called taper-current) earlier and longer. So no major damage.
But it does allow the unknowledgeable consumer the ability to use a charger - no higher than 15A - they may have off the shelf and make the battery sale.
YOU - however, being more knowledgeable now, will limit your charger / controller choice to something no larger than 10.5A for a more efficient charge. (stay between 0.25 to 0.3C max)
Double that for two in parallel as the max. Or triple it for 3 in parallel and so forth - assuming they are well balanced - but that's a different subject.
Which for a 35ah agm, a max of 10.5A at 0.3C.
But why the 15A max rating? This is simply to try and accomodate consumers and extend the *possible* range of chargers they buy off the shelf.
What will happen in the real world, is that even tough 15A is too high on paper, because nearly ALL modern consumer chargers are of the cc/cv type, the cv will be reached quicker than normal, and the battery will be in the cv mode (the so-called taper-current) earlier and longer. So no major damage.
But it does allow the unknowledgeable consumer the ability to use a charger - no higher than 15A - they may have off the shelf and make the battery sale.
YOU - however, being more knowledgeable now, will limit your charger / controller choice to something no larger than 10.5A for a more efficient charge. (stay between 0.25 to 0.3C max)
Double that for two in parallel as the max. Or triple it for 3 in parallel and so forth - assuming they are well balanced - but that's a different subject.
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MisterSandals
Participation Medalist
This won't do anything noticeable. You need some current flow, preferably charge current to properly balance them as a pack.
If the voltages are close, within a couple tenths of a volt, connect them as you said. You need to connect this pack/bank in a balanced manner from each end: positive to battery 1, negative to battery 5.
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