I'm going to add a final note here just in case we haven't already beaten this subject to death. As I mentioned, I had a trailer battery go bad and had to replace it recently. I brought both the one good "old" battery and the new battery separately up to full charge with the Battery Maintainer, and then I installed the new one in the trailer (they're connected in parallel of course). I put the Battery Maintainer on again and left it connected for a couple of days.
I disconnected the maintainer and 24 hours later, checked the battery voltage. It read 13.03 V. Now, I know my trailer has NO parasitic draw at all (I've verified that with an ammeter), so I doubt you'd see a figure this high if the battery was installed in a truck, but, it DOES lend support to the claim that a fully charged battery will show about 12.9 V in a "resting" state.
The reason I brought both batteries to full charge separately, was because I wanted minimal "imbalance" between them when I connected them together.
- Jack
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