danw
Lifetime Supporting Member
Your attached DVM photo (post #1) shows a value of 7.2V. But that's more than an expected 6.0 volts from a the 1:2 voltage divider across a 12.0V battery.
But if the battery was in a charging circuit, 7.2V is about where a lead acid 12V battery charges: 14.4V.
If you have a charger involved, the DC side is probably at different ground potential, causing common mode problems for a single ended AI (a typical symptom of that kind of problem is that the other channels are affected).
The test of a charger-related problem on a single-ended AI would be to disconnect the charger and see how a floating battery works on the voltage divider/AI.
But if the battery was in a charging circuit, 7.2V is about where a lead acid 12V battery charges: 14.4V.
If you have a charger involved, the DC side is probably at different ground potential, causing common mode problems for a single ended AI (a typical symptom of that kind of problem is that the other channels are affected).
The test of a charger-related problem on a single-ended AI would be to disconnect the charger and see how a floating battery works on the voltage divider/AI.