Aug 08, 2026

I learned a few things about electricity. The boat came with a trolling motor directly connected to a battery, so I had to figure out the proper protection. The first iteration was two manual circuit breakers: one between battery and power bus and another between power bus and the motor. I checked the prices for marine equipement, and tried to save money by going with cheap automotive breakers. That was a mistake. A no-name $10 breaker seemed to work fine in a short test, but under the load of high speed setting, the motor was shutting off within two minutes. This got me into a peculiar situation while passing through a narrow channel, and later when undocking in high beam wind. Turned out, each breaker was dropping substantial 0.45V and was overheating. The BMS (battery management system) was detecting high voltage drop, and was disconnecting the circuit. I upgraded to a proper fuse sitting right on top of the positive battery terminal, and a proper brand marine circuit breaker. The new system drop 0.1V on both connections when drawing ~42A, which is considered a bit high. But the BMS no longer trips, and I can go on high speed reliably (tested with a 15 minutes run). The battery side of the breaker heats considerably, so that I can touch but can’t hold it in my fingers. I checked the lug contact, made sure it’s clean and snug, the heat seems to come from inside the breaker. Not ideal, but manageable. I rarely need to go on top speed for longer than a few seconds.