Testing 6V Deep Cycle Batteries

wgriswold wrote:

MrWizard wrote:
testing at 12v is correct
if you think golf cars, don't pull a heavy draw from batteries
you need to do some reading

There are three types of batteries we all see. Starting batteries such as are in our cars. Hybrid starting/deep cycle batteries that are used in Rv's and boats and perhaps other places. And deep cycle batteries, usually 6V GC batteries in our RV's.

These three types are designed differently for different purposes. There must be some reason deep cycle batteries are not designated starting batteries, but I have to admit I don't what it is. The demands of a golf cart must be different than the demand of starting battery.

I suspect that an instrument designed to load test a starting battery may fail to properly test a GC deep cycle battery and that was my original question.

Thanks, everyone, for your help. It seems that the consensus is that an auto parts store tester is not the appropriate tool to test a GC battery.

I originally was questioning the batteries when I was on a trip and turning on one light made others dim. I had not seen this before and so was questioning the batteries. I had a volt meter and the voltage was OK, but my specific gravity tester was at home, so off to the auto parts store I went.

After I got home my battery disconnect switch failed and I suspect that may have been the cause of the dimming as resistance increased across it during its failure process.

A 6V GC2 battery has thicker plates, a larger electrolyte chamber, and a more robust connecting grid. There are also differences in paste configuration and alloys but I can't really speak to that. Basically, it is engineered for a longer, more constant, draw period and to endure more shock when in motion.

A simple load tester (as used in the parts store) in the hands of someone experienced, may turn up a problem with a pair of 6V batteries. The more general problem of the load test being accurate, is the complication of who's doing the testing. Most counter personnel are barely qualified to sell the correct wiper length. The auto parts business doesn't nurture older, experienced and more qualified, personnel.

I'd assume that the exchange at Costco did not involve any testing. A look at the date stamps on the battery cases was all that was necessary? At least you found the source of your power problem. Limiting the charge through the failing disconnect switch would have meant another trip to Costco in the future.