Testing 6V Deep Cycle Batteries

According to this guy, the Napa store tester won't cut it.

Batteries+, they know what to do

Buy yourself a hydrometer, learn to use it.

Testing them in series is proper. Using a starter battery tester for deep cycles is not really a great method.

First: I'm fond of saying "There are no six volt batteries in RV's" (And I get flamed if I don't go on to explain that)
What there are (Less than six feet from my feet) are 12 volt batteries which for ease of handling have been split into two parts (And other reasons, like cost) 1/2 of the battery is 4 times easier to wrangle, and as the GC-2 is the single most popular Lead Acid battery.. Lower "per unit" cost due to the economy of scale (THe more you make before re-tooling which the 6 volt lines basically never do, the cheaper).

So testing the pair as a single 12 volt battery is exactly how I would RECOMMEND doing it.

It 9is also how I do it

Since both the store's tester, and mine, are designed for 12 volt batteries.

Another thing:
WOuld you buy a 12 volt battery if half the battery was say 2 years old and the other half brand new?

NO and neither should you.

WHen you replace 1/2 of your 12 volt battery (one six volt) replace the other (It's mated partner) as well.

Why did you have them tested?
What method of charging are you using?
Had the batteries ever been run flat dead or low on water (below the plates)?

wa8yxm wrote:
Another thing:
WOuld you buy a 12 volt battery if half the battery was say 2 years old and the other half brand new?

NO and neither should you.

WHen you replace 1/2 of your 12 volt battery (one six volt) replace the other (It's mated partner) as well.

Hmmm .... I'll have to think about that for a minute: In what way could a bad 6 volt battery in series with a good 6 volt battery in any electrical way, shape, or form damage the good battery?

This seems like a different situation altogether from one bad cell in a 12 volt battery causing the whole battery to not supply enough voltage to be of any further use - such that you have no choice but to replace all of the cells ("the whole battery") at the same time.

If I had two 6 volt batteries in series in my RV and when, after charging both together, the voltage then was lower than full charge voltage, or the current delivery then remained lower than what it used to be when they were new - before paying for two new batteries I'd want to know if only one of the two batteries was bad.

The above would especially be what I would do in a situation of "early failure" in which one of the two 6 volt batteries went bad sooner than it should have such that I now had an unsuable 12 volt battery bank in the RV. IAW, why replace both 6 volt batteries in a series string when only one may need replacing?

A slight problem might be where to go to get a 6 volt battery tested? Some/most auto parts stores may not be able to do it. Probably outfits like Batteries Plus can check individual 6 volt batteries, however.

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

cars used to have 6v systems and 6v starters
the change to 12v let car mfg use smaller wire for everything

you had a concern, you took the batteries for testing
costco exchanged them and gave you New batteries
No more concern, its a WIN !

The auto parts stores serve a function--to test batteries that customers bring them to see if they're operable. An owner can do some testing at home if he has the right measuring gear, a meter and a hydrometer. The load testers at the auto parts stores may turn up a failing battery/-ies, also.