Battery Cutoff Switch (1 Viewer)

[ntsqd]

Two batteries. How are they actually connected to each other and the vehicle? If they are connected positive to positive and negative to negative with heavy cables, and then the vehicle's positive vehicle connection is at one battery and the vehicle's negative connection is at the other battery then a battery switch in either vehicle connection will disconnect the batteries from the vehicle.

If that is not how it is wired then pictures are likely going to be needed.