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Best test to determine health/remaining life of batteries

March 26, 2014, 11:23:47 am

I know this has probably been discussed here before, but I could not find a good answer.

What is the best method of determining the health and remaining life of an AGM battery? A gel cell battery?

I called East Penn Mfg (Deka batteries) customer service and the guy that question. He said "Well, uh, duh, uh... do you have a voltmeter?" Me "yes". He said "Well, uh, you I guess you could test the voltage." I am not really impressed with Deka/East Penn. Where do they find these people to represent the company?

I also emailed Lifeline, but have not heard from them.

So I know I'll get better answers here from the real experts.

Thanks

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Re: Best test to determine health/remaining life of batteries

Reply #1 – March 26, 2014, 11:39:36 am

The technical guys will I am sure answer better but my first joking thought was the deka guy rarely has failures.  Service life is 1,000 50% cycles on their 8g8d gels.

5,000 cycles at 10% on their chart.

Most post 9-10 year lives here.  More batteries the better.  Lower the discharge percentage and they last longer.  Duh.

Solar to keep them up probably pays partially for its costs in increased battery life.

Bob

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Re: Best test to determine health/remaining life of batteries

Reply #2 – March 26, 2014, 12:03:59 pm

The only reliable way to test the remaining capacity of a battery is a real world test.  Charge it up and put a load on it and see how long it runs until the battery reaches terminal voltage usually 25 amps. Terminal voltage is when the voltage drops to the manufactures spec. for the lowest recommended voltage before recharge is needed.  Typically this is when 50% of capacity has been used, but this depends on your battery's specs.

Remaining life will depend on many variables such as loading, number of deep discharges, operating temperature, physical environment etc. so it's not possible to be really accurate unless the battery is in a steady operating environment.

In other words you can get a good estimate only.

Here is a document that describes how it is done in the shop.

http://www.phillipsind.com/upload/reference_material/file_1236015433.pdf

I should add that this subject is like the discussions of oil.  One gets lots of opinions, and a few facts.

Keith

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Re: Best test to determine health/remaining life of batteries

Reply #3 – March 26, 2014, 03:09:59 pm

A couple of years ago I ran a test.  I hooked up a voltmeter and clamp on ampmeter and turned on a bunch of lights. I measured the voltage and amperage each hour until the batteeies were at 50% based on voltage. I did the math and decided my 8 year old batteries were still 80% of original capacity. They were strong until one developed an intermittently shorted cell. My new Lifelines appear to have about the same capacity as my 10 year old batteries had just before the end.

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