Thread: Start/Accessory Batteries

Originally Posted by Dutchman

Installing 2 group 31 deep cycle AGMs up front for 24v Terrova. I am planning on running dual batteries on 12 volt system for outboard and accessories. My question is , what size/type batteries do I need for outboard (60hp 4stroke EFI) Helix 9 ,Helix7, livewell, 2- 10 foot LED light strips, bilge pump ? Would start or deep cycle be better in this application ? What group size ? I have plenty of room in rear since I am moving trolling batteries up front. Thanks in advance.

The best way to set it up would be to use a group 24 starting battery for just your motor and dash gauges, then pick up a 27 or 29 dual purpose and run everything else to that battery. You can use deep cycle for your second battery, but the dual purpose will have enough CCA and MCA to start your motor if your starting battery ever fails and is made to act like a deep cycle in terms of slow and long discharge.

Like Kevin said. Putting all the extras on your cranking battery is a good way to leave you stranded. Best to run everything also to a separate deep cycle or dual
purpose then you have a backup as well.

Group 24 start battery for outboard, and gauges. Group 27 Deep cycle for electronics , and lights. Thanks guys!!

I had a guy tell me that you should put a battery switch in between the starting battery and the battery for the FF. That way you can switch the starting battery off during fishing times and switch it to charge the FF battery after you start the big motor. Anyone else set it up this way?

Originally Posted by timd3200

I had a guy tell me that you should put a battery switch in between the starting battery and the battery for the FF. That way you can switch the starting battery off during fishing times and switch it to charge the FF battery after you start the big motor. Anyone else set it up this way?

Sounds like a PITA to me to be honest.


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Originally Posted by timd3200

I had a guy tell me that you should put a battery switch in between the starting battery and the battery for the FF. That way you can switch the starting battery off during fishing times and switch it to charge the FF battery after you start the big motor. Anyone else set it up this way?

I'd be leery about doing this. If both batteries are low that's probably too big a load for the charging system on some outboards

"I had a guy tell me that you should put a battery switch in between the starting battery and the battery for the FF. That way you can switch the starting battery off during fishing times and switch it to charge the FF battery after you start the big motor. Anyone else set it up this way?"

I don't really see the need to do this. I run my FF all day off of one battery and never had a problem going dead. As long as your battery is good you shouldn't have a problem.

Large deep-cycles and multi-battery setups are not recommended for Mercury outboards with stators. The regulators aren't designed for a continuous high charging load and you will see accelerated regulator failure.