Trolling Motor Battery Setup Question

[Carl]

If I have two deep cycle AGM batteries @ XX AH each running a trolling motor, which setup gives me longer overall run time:
1. Wire them up to run in parallel, with a 60amp circuit breaker/switch to isolate the TM from the batteries when not in use.
2. Install a 3 position switch (1, Off, 2), connect each battery to the switch and run them separately, switch over once the first battery drops below 10% charge remaining.
3. Or does it really even matter?

 

[SJ Fairbank]

I've seen boats rigged both ways. I believe the vast majority of 12v motors are wired separately, I'm assuming your motor is 12V. The 24V motors need two 12V batteries rigged in series to up voltage, or a 24V battery. The total output (amphours) doesn't increase by wiring in parallel. If you have two 100AH batteries in parallel, you still only get a total of 200AH. My concern with connecting them is if one goes bad, it could short the bank and drain battery #2. My preference would be the switch, isolate the batteries. But either option will work.