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post #10 of Old 11-01-2013
Chas H
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Re: Uneven Water Loss in Batteries

A specific gravity test (hydrometer) is a good way to test a lead-acid storage battery. A fully charged battery will have a specific gravity around 1.260. Hopefully the difference between cells is no greater than .05. (The specific gravity of water is 1.0) A hydrometer reading below 1.225 shows a discharged battery or maybe a sulfated battery. A sulfated battery will not take a full charge because the sulfuric acid has hardened on the plates (lead sulfate) like dry peanut butter on a knife. A sulfated battery may have a high voltage reading but it's only a trick. Don't believe it. As a battery charges the sulfate (sulfuric acid) comes out of the plates increasing the specific gravity of the electrolyte. Hydrogen is released during charging hence the need to add water. I'd guess hot Florida weather cause evaporation beyond what we see in more temperate climes.

Another twist is plate grid material which changes required charging voltages.

A load test is a better test, but requires test equipment beyond what most people have in their tool pouch.

Specific Gravity of Battery Electrolyte - Engineers Edge

- CH
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