I now have two fully charged batteries. I've taken the automatic relay out of the system. I'm attaching a diagram. If I read this properly any time there'd be a charge on the system then the relay would connect both batteries, in effect bypassing both switches. I'm not sure that's really helpful.

Even if they had gone bad I can't see how the two switches would have caused the batteries to fail. That leaves the controller and the automatic relay. The latter is out of the picture now.

While working on the batteries I ended pulling on one of the strops that keep them latched down and it came right off. I re-secured those strops.

I re-bedded the stern hatch latch screws to prevent some of the leaking there.

Tomorrow I'll re-install the batteries and will do a few tests:

1. Controller: voltage before and after controller; voltage after solar panel fuse;
2. Switches: make sure they do their jobs;
2.1. Charge in switch: connect one battery only, switch to that battery and controller should show charging; switch to the other battery (absent) to see lack of charging; switch to 1+2 to see charging. No load on this.
2.2. 12 V panel out switch: same testing but test with load (e.g. cabin light)
3. Measure voltage in each possible configuration.

I wonder if it's possible for a solar panel to go bad. Or maybe there's something wrong in the fuse panel/load, causing constant discharge and the tiny solar panel can't keep up, causing chronic low charge? I'm not sure because I regularly checked the voltage and it looked good.

Name: Battery diagram.jpg Views: 667 Size: 1.73 MB