DRAGONFLY Trimarans User Forum

When unplugged from shore power the parallel battery switch on the electric panel turns off after a while (10 minutes). I guess it's as expected to prevent autopilot/instruments/etc draining the starter battery. However when this happens the voltage on the starter battery circuit as shown by the panel indicator goes to zero (0.0) and the motor can't be started at all. Sometimes the parallel switch even switches off when the motor is running and the engine stop button can't be operated. I have replaced the starter battery to fix this and it didn't help. I replaced the Blue Sea ACR and it didn't help. If there is a break in the starter battery circuit then why does the parallel switch stay on for a while? This happens even with the manual switch on the Blue Sea ACR (7622) in the "parallel" mode.

I can't figure this out, need advice from someone more familiar with boat wiring.

I looked up the specs on the ACR.
It says it disconnects at ten seconds @ 12.3 V. or thirty seconds @ 12.75 V.

I suspect a high resistance connection from the start battery.
Check the negative lead connections for corrosion or loose connections.

If there is no load on the start battery, a high resistance connection will transfer voltage without significant drop, but when the battery is presented with a big load (starter), the voltage drop across a bad connection will be nearly 12 volts.
The result will be no starter action.