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I received a query from one of our readers today that is worth sharing. Although not too popular at the moment, this fellow is working on a boat with a 32 volt DC system. Some years ago these systems were quite popular. Not so much today. I spend more time answering questions about how to convert the older boats from 32 volts to either 12 or 24 volts. The question regards the use of conductance battery testers such as the one I use shown here:

Midtronics EXP Conductance Battery Tester

Anyow, the question goes like this:

Hello Ed,
I am a student working with a 32volt system and wanted to ask you for your advice with the system. Specifically how you might diagnose overall battery bank health with a conductance tester. Is it possible to do or must you break the bank apart into its components analyzing each component battery individually? I have very limited experience with such a tester but want to develop an understanding of its usefulness. If it is the case that the tester is not applicable to the 32volt system then I am relying on the congregated info regarding each battery within the system and as such I am interested in your approach when summarizing the overall health. I guess ultimately I am more interested in your tactical approaches with the larger 32volt systems then individual battery analyses. Any thoughts would be greatly appreciated.

Thanks, Zander

Bad news Zander. All of the units I’m familiar with only work with either 6 or 12 volt batteries. My EXP unit shown above will also test 12 and 24 volt charging systems. I believe that your 32 volt system is using 8 volt batteries, which these days are quite rare in the marine realm.

They are still used in electric golf cart applications for extreme deep cycle applications. So, even if you isolate each of the batteries in the system and test them individually, I’m not aware of a conductance tester that will work with them. Maybe another reader has found one that does?

As for the value of separating each battery in a paralleled system and using a conductance tester I have done it on new installations that weren’t too large to see how it would play out. As long as your tester can be programmed for the maximum cumulative CCA that the parallel combined batteries are rated at, you can give it a go.

My unit is good for a maximum of 3000 CCA. But frankly, I don’t recommend this method as the most accurate. Small things like cable connections can make this dicey. These meters are really quite sensitive to any electrical resistance that exists and even a slightly loose battery cable clamp can throw your readings off.

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