Can I run 12/24 TM, start my big motor, an run my fish finder with only 2 batteries?

[honda460ex]

Had a 12 volt 33lb thrust TM and was given a nice Motorguide 56lb thrust 12/24 volt TM for my 17ft Fiberglass Bass Boat. Wanted to change the 12 volt out without adding any more weight to the boat if possible. I currently have two batteries in the boat. Both are deep cycles. One is used for starting the big motor, running lights, bilge pumps and fish finder. The other has strictly been trolling motor only. New TM is a 3 wire setup. If I set my wiring up for the 3 wire 12/24 volt setup could I still use the first battery in that setup to start my motor, run the lights at night and run my fish finder while not frying any of it? I know regardless some people are going to disagree with this being done even if it can be done, but I don't care about that right now. I understand all the risks of running out of juice on the water and not being able to crank the big engine and the affects it could have on the batteries. I just want to know if it can be done without hurting any 12 volt components I have in the boat now. Any help is appreciated!

Thanks!

 

[Silvertip]

Re: Can I run 12/24 TM, start my big motor, an run my fish finder with only 2 batteri

The answer is yes -- BUT!! The engine can only charge one of the batteries since the two batteries must be connected in series for the 24 volt troller. If you run the troller on 12 volts only, then that makes things a little more tolerable and the engine can charge both batteries. The other down side is that if you run the troller on 24 volts, run-time will be very limited since the battery used for starting and accessories will be discharged at a much greater rate than the other.

 

[j_martin]

Re: Can I run 12/24 TM, start my big motor, an run my fish finder with only 2 batteri

But

If you run it as it is now, with all the little stuff on the starting battery, the engine will usually charge it enough to keep up with the extra discharge, and the draw down will even out.

I've done it. It works fine. Just be sure you can rope start the engine if necessary. Also, you will have to routinely charge up both batteries instead of just charging the trolling battery.

Also, don't run the troller on 12 volts, ever. Look at the discharge curves and do the math. You'll see why.

 

[honda460ex]

Re: Can I run 12/24 TM, start my big motor, an run my fish finder with only 2 batteri

Thank you both for the answers and advice! Greatly appreciated!