It appears that my boat, which was purchased with on-board chargers and 24 volt trolling motor voltage, charges only the two batteries for the trolling motor.  On my old boat, I installed an on-board charger that charged both the trolling motor battery and the starting battery.  Note that the electronics (fish finders, 2) are on the starter battery on the new boat.

 

Is it possible to wire the two on-board charging circuits to include the starting battery?  I would think that wiring the starting battery in parallel with one of the trolling motor batteries would work.  Anyone know whether I'm right or not?  Thanks for your expertise.

This doesn't answer your question, but there's no way I'd do that. 

 

Seems like a band-aid and doesn't address the real problem, which is that you likely need to charge the starting battery because the big motor doesn't get it done (in my case, I never make long enough runs).

 

Couple options, I've done both:

• Pull the two bank charger and replace it with a three bank.  Sell the two bank on Craigslist, or E-Bay.
• Add a single bank charger for the starting battery.

I agree with your comments.  I think that my engine is not providing adequate output from the alternator, and when I get that fixed, it may be OK. If not, add a single bank charger.  thanks, Mick

5 hours ago, MickD said:

I agree with your comments.  I think that my engine is not providing adequate output from the alternator, and when I get that fixed, it may be OK. If not, add a single bank charger.  thanks, Mick

It really depends on how far you run.  The longest run I can possibly make on the lake I fish most often is 10 minutes.  That's not near enough to top off a battery that's been running electronics all day.

Your motor should only be charging your starting battery where all of your accessories should also be connected.  There should be nothing on your trolling motor batteries other than your trolling motor.  There are products out there that will connect your big motor to charge the Trolling Motor batteries after the cranking battery reaches full charge.  There are also battery jump switches that allow you to loop in (via the switch) your troller batteries to start your big motor in the event your cranking battery won't.  I have 4 batteries total (3 TM, 1 cranking) and I have a 4 bank on board charger.  I would never rely on the big motor to keep the cranking battery charged up.  It takes just as long to charge with my on-boars charger as the trolling batteries that get no help from the big motor.   

54 minutes ago, TOXIC said:

Your motor should only be charging your starting battery where all of your accessories should also be connected.  There should be nothing on your trolling motor batteries other than your trolling motor.  There are products out there that will connect your big motor to charge the Trolling Motor batteries after the cranking battery reaches full charge.  There are also battery jump switches that allow you to loop in (via the switch) your troller batteries to start your big motor in the event your cranking battery won't.  I have 4 batteries total (3 TM, 1 cranking) and I have a 4 bank on board charger.  I would never rely on the big motor to keep the cranking battery charged up.  It takes just as long to charge with my on-boars charger as the trolling batteries that get no help from the big motor.   

This is true unless you have long distance to run on the big motor and use you TM to move withing spots.  I have a MK  alternator that can top off my TM batteries for my mid week usage but will not compensate for tournaments 

I realize there are products that can switch etc, but I have a very "clean" boat and don't want to get into running new wires and mounting new switches unless a last resort.  I have room right in the starting battery compartment for a single bank charger, and that would be the cleanest, most reliable fix.  thanks for all the comments, much appreciated.

I would just get a 2 or 3 amp charger and charge the crank battery separately 

Just ordered a 3 amp on-board charger yesterday, thanks, Mick

On 6/25/2018 at 8:00 AM, TOXIC said:

 It takes just as long to charge with my on-boars charger as the trolling batteries that get no help from the big motor.   

Quite the opposite for me. My cranking battery with the on board charger is usually at 100% within 10 minutes. I also typically am not making long runs. The trolling motor batteries take far longer to reach 100%. Are you sure your alternator is actually putting out a charge?

7 hours ago, Krux5506 said:

Quite the opposite for me. My cranking battery with the on board charger is usually at 100% within 10 minutes. I also typically am not making long runs. The trolling motor batteries take far longer to reach 100%. Are you sure your alternator is actually putting out a charge?

I will have dealer check it on my next trip in for other work.  I'm not convinced it is putting out what it should be, but one indication that it is working to some degree is that the voltage indicated on the fish finder is higher when the engine is running than when it is not running.  How are you defining and measuring 100%?  thanks, Mick

9 hours ago, MickD said:

I will have dealer check it on my next trip in for other work.  I'm not convinced it is putting out what it should be, but one indication that it is working to some degree is that the voltage indicated on the fish finder is higher when the engine is running than when it is not running.  How are you defining and measuring 100%?  thanks, Mick

True, that is a good indication regarding the voltage reading on the fish finder. The only way I'm measuring 100% on mine is based on what the charger is indicating.