How do you wire three 12V batteries in series?
Use a three-battery bank only when the exact equipment and battery manuals permit it and identify a compatible setup. Switch the load off and isolate it before working on the bank. Label the batteries 1, 2 and 3. Connect battery 1 positive to battery 2 negative, then battery 2 positive to battery 3 negative. The two free terminals are the bank output: battery 1 negative is the negative output, and battery 3 positive is the positive output. The linked Minn Kota series diagram shows this topology for its specified trolling-motor systems. A 36V bank is nominal; measured voltage varies with charge state.
Where do the equipment leads go?
The equipment manual’s diagram governs the exact lead connections. Connect the positive and negative leads only to the corresponding free bank terminals and only as the diagram shows. Check the equipment’s required voltage, battery configuration, cable ratings and protection before connecting the load. Do not connect a 36V bank to 12V or 24V equipment.
Check before connecting a load
With the load isolated, verify polarity and bank voltage at the free terminals using a suitable meter. Stop if the result does not match the equipment specification. Follow the battery and equipment makers’ instructions for wiring and reconnection; ask a qualified technician if the diagram or protection requirements are unclear.
Sources: Minn Kota: Connecting Deep Cycle Batteries in Series or Parallel
