What is maximum charge current into lead acid battery?

[D.A.(Tony)Stewart]

ESR losses in a battery are related to SOC , Battery quality and Ah capacity and CCA rating.


I would fully charge the battery and determine the constant current rise from 12.8V to 11V and use that current as the maximum. Thus when discharged at 11.5 going to 14.4 or so (which is a function of temperature) is a 1.6V rise above fully charged. You can compute I^2*ESR power , but dont't boil the electrolyte. ( listen to it) C/10 C/5 , C, 5C charge ratings etc always depend on battery design, so I expect they assume high Quality batteries.

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SAE J537 standards by applying a full charge and a 24-hour rest, followed by a regulated 25A discharge to 10.50V (1.75V/cell).

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The above was for Ah capacity testing.. I recall CCA testing used 0'F but no matter it involves reducing 12.5V full charge to 7.5V sustained current for so many seconds (30?) for SAE specs, other standards have different voltages like 8.5 9.5 with higher duration times.

This would obviously overheat the battery if used for charging, but I suspect there is a fractional ratio of CCA for maximum Charging rate.
e.g. 700Ah car batteries routinely have alternators rated at 70 to 100A or 900Ah ones usually on cars with big V-8s with 120A alternators.

I suspect this ratio is 10~15%.

A 5Ah battery is pretty small so a 1C rate of 5A is safe a 4C rate of 20A expects that these are the best quality fresh batteries. otherwise heat rise, gassing, electroplating are all concerns. Heat rise actually improves performance (Lower ESR) but increases aging rate and sulfation rate.

I doubt if the Charge rate is 20A that it has a CCA of 10x this amount, so I would be concerned.

 

[treez]

Thanks, I asked what the battery capacity was, and they said 5A.h but didn’t sound sure. When I asked again why such a big battery was being used to turn on the contactor to the HV battery, they just said that the battery was sometimes used in petrol/electric vehicles. –Presumably, by that, they were implying that it might have to be used as a high current starter battery…however, 5Ah is surely too small for that kind of use?
They have re-iterated that I must current limit the 14.4v, 300W full bridge converter, so that it puts 20 Amps into the battery, when the battery is flat. They seemed to say that if the battery was totally flat (10V) to start off with, then if 20A was put into it, then it would be ok because within about 30 seconds the battery voltage would go up to about 13.8V or so, and that the charge current would thereby reduce.

 

[Warpspeed]

In an EV, any gasoline engine used for recharging the main traction battery is not likely to be very large.

Quite a few high end motorcycles have electric start, and as far as I know the batteries are just normal average motorcycle size, similar to yours.

 

[treez]

In an EV, any gasoline engine used for recharging the main traction battery is not likely to be very large.

I thought in most "hybrid" EV's, the gasoline engine is not for charging the main traction battery, but is for literally powering the wheels from the combustion engine when the batteries run out?

 

[Warpspeed]

You don't need a high capacity charging source if the gasoline engine runs continually at full throttle. You only draw big amps when actually accelerating.
Once reaching a reasonable road speed, current draw should be minimal.

Meanwhile you little gas engine is chugging away merrily still absolutely flat out.
The battery is the big energy reservoir, but the gas engine need not be huge to keep it topped up.

 

[treez]

thanks, so you appear to be saying that a "hybrid" vehicle only uses the combustion engine to top up the power traction battery...so in other words, the 5A.h (so we believe) battery of this thread is never used to actually crank the engine. In that case, why does it need to be 5A.h?

 

[treez]

Also, is it right that a totally flat 5A.h lead acid battery, at 10V, can be suddenly connected to a 20 Amps current source, and THEN within 30 seconds, its voltage will be up to 13.8V?
Also, the following states that a hybrid EV has an internal combustion engine which drives the wheel, not charge the HV power train battery

https://en.wikipedia.org/wiki/Hybrid_electric_vehicle

 

[BradtheRad]

Also, is it right that a totally flat 5A.h lead acid battery, at 10V, can be suddenly connected to a 20 Amps current source, and THEN within 30 seconds, its voltage will be up to 13.8V?

A depleted battery quickly jumps up in voltage when you start charging. It may reach 13 or 14V because you are forcing high A through it. It will drop after you stop charging. After some hours it settles at a voltage indicating its state-of-charge.

Theoretically a 5AH battery will fully charge in 15 minutes at 20A. It is a severe charge rate for a lead-acid type.

 

[treez]

thanks

as the following says, the Plug in hybrid electric vehicle (PHEV) has an internal combustion engine, but this does not power the wheels, it only acts to re-charge the battery, so the need for a big LEAD ACID auxiliary battery just to switch the contactors oF the power train battery remains a mystery.

https://en.wikipedia.org/wiki/Hybrid_vehicle#Parallel_hybrid

 

[mrinalmani]

Hi!
I have charged fully flat 26Ah lead acid battery several times using different methods.
You would expect it to draw maximum current when it is fully discharged at around 8V. But this doesn't happen. At this stage it pulls no more than 6 to 7A. The battery voltage rises to the charger voltage quickly. At no stage does it pull more than 25A.

 

[FvM]

At no stage does it pull more than 25A.

You're apparently talking about an old, exhausted battery with increased internal resistance. Don't jump into conclusions.

 

[chuckey]

Its a commercial decision, Chrysler use a 15V alternator with a current limit of 50A for their new vehicles. They don't have to pay for the new batteries as they are tested to make sure that the batteries last the one year warranty period.
Frank

 

[mrinalmani]

Yes exactly! The battery is old.