Dual voltmeter
I went direct to the 2 batteries to ensure I had their voltage, which may be different than the One Control Monitor Panel chassis voltage.
I didn't see (or really look for) a different point like you suggested.
My batteries didn't go dead due to lack of water (at least while I owned the coach). Mine happened under the dealer care....the wouldn't hold a charge, read 3 volts and 6 volts when disconnected for replacement.
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