I want to make a backup battery connector for my project so I can power it externally if the internal battery dies.
For this, I'm planning to use a SPDT switch with the pole connected to the circuit's power input and the throws connecter to both the batteries positive terminals. In this way, the grounds of both the circuits will be connected to the circuit's gnd input all the time.
Is this okay? When I'm powering it from battery one, battery two's ground will also be connected to the circuit's gnd. Won't current flow from one battery to another?
Should I use a DPDT switch to switch both positive and negative wires?
Thanks a ton.