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An easy way to find faulty a battery?

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I have 8 100Ah Omnipower AGM batteries running in a 4S2P configuration for my 48V inverter. I suspect one or more of the batteries have been damaged or is just not balanced any longer because the voltage seems to drop much quicker under load than they use to. 

I now want to find the offending batteries and test them to see what is going on. What would be the steps for me to test the batteries and possibly try and re-balance them? I have access to a multimeer and a normal non-smart battery charger(Hawkins Pro 15 Battery Charger 12/10G). 

My problem comes in with not having access to a smart charger but only a normal battery charger as I'm not sure if I can charge a battery using it and I don't have mega bucks to spend on a smart charger.

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Process of elimination. Put some load on the inverter, and measure each battery with the multimeter. The bad one should have a lower voltage while under load. Then put it under charge and repeat. The bad will most likely (though not always) rise faster than the others. By temporarily taking one string out of the equation you can isolate the bad string and also exagerate the problem a bit (with parallel strings, the good one tends to pick up the slack and it's less noticable).

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connect  one of those cheap led voltmeters on each battery . switch off the solar and Eskom and place some load on the system and watch the meters  you will soon notice what's what

cheers

 

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What I do, for I have used the volts and load test, I disconnect the bank and test each battery under load, tested like they do at the car battery shops with their testers.

A 100ah battery will be subjected to 300amps (3 x batt ah) pulled from batt for a few seconds. You will be surprised at the results.

The volts will give you an idea yes, but you could find another battery, under extreme amps after volts tested fine, is also going.

With all the testing I have done on large batteries, and the resultant pain, I now only test them individually.

Ja, I know it is a shlep, a huge one, and frustrating to connect and disconnect. But in the end you can catch the weak ones a long time before they damage the rest, or explode. 

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On 12/25/2017 at 4:04 AM, plonkster said:

Process of elimination. Put some load on the inverter, and measure each battery with the multimeter. The bad one should have a lower voltage while under load. Then put it under charge and repeat. The bad will most likely (though not always) rise faster than the others. By temporarily taking one string out of the equation you can isolate the bad string and also exagerate the problem a bit (with parallel strings, the good one tends to pick up the slack and it's less noticable).

This worked great for me. Six of my eight were at 12.3V. Two of them sitting next to each other in a string are at 12.6V and 11.9V. What do I do now?

Note:

I recently ran an AGM RECONDITION cycle on each individual battery with a CTEK 5amp smart charger. I put the bank back together this morning. Everything seemed to equalize out fine. Mid-point voltage looks good on the 702, but this evening I checked with the volt meter and found the above discrepancy.

I hooked my CTEK charger up to the low volt battery while it is in the bank. Thinking this will maybe act as a balancer. 

 

 

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