Marine battery acting strangely
I have a new 12V deep cycle marine battery in my camper trailer. When charging, it immediately (within a few seconds) goes to 15.0-15.1 volts. This is happening with three different charging sources: the converter in the trailer, the 100 watt solar panel & Morningstar Sunsaver charge controller in the trailer, and my automotive battery charger. The thing is, the battery passes a load test with flying colors. I had a similar situation a couple of years ago with an Optima battery in one of my trucks. The battery was showing 17 volts while charging. After replacing two alternators, I finally realized it was the battery itself. What causes a battery to do this?