Mysterious Nighttime Battery Drain and Solution

Zombiecat

Well, this was a pain over my summer travel so I hope this post will help someone else who experiences a similar issue.

I suddenly began experiencing battery drain at night while boondocking. At first I noticed that my lights were dim, then everything powered by my battery lost power. My Victron app showed a drastic reduction in battery voltage within one hour after sunset. I checked my WFCO control center - no blown fuses - but I replaced them all anyway. I also replaced all the fuses on both my battery and solar controller. Note that while on shore power or towing, everything worked perfectly. Thankfully, I use a Jackery power station while stationary to run my refrigerator.

I finally resorted to taking the only service appointment at a NuCamp dealer, 640 miles away, but at least in the right direction for my travel. After three days in a hotel and a hefty bill, they pronounced it repaired. They had replaced the battery and battery cables (incorrectly, but that's another story!). 

I backtracked a few hours to my next scheduled stop, only to discover that once the sun went down, my battery STILL drained and I again lost power. Once I returned to civilization, I contacted a local mobile RV repair guy. When he arrived the following morning, he suggested that my Victron solar controller was the culprit. At his direction, I tested the system overnight by disconnecting the controller from the solar panel, while leaving it connected to the battery power. I didn't use any battery powered items overnight and the battery maintained a full charge. Aha! 

Our guess is that there was a bad diode in the solar controller, allowing the current to "backflow" into the solar panel. I ordered a replacement Victron solar controller through Amazon (about $60) and replaced it myself. All seems to be working properly. I'm unhappy with the RV dealer, who failed to diagnose the problem and didn't properly install the new battery and cables. I wasn't able to return to them to correct the issue, as I was now in another state, but I did negotiate a partial refund.