trolling motor batteries discharging

[FireCapt]

I have a Motor Guide 12/24v trolling motor with two 27 series batteries. I have a console with a three position switch: Run/Off/Charge.

The problem is when I switch to "Charge" it causes both batteries to discharge fairly quickly instead of charging the batteries. This is a new problem as it has worked up until now. It has not affected my cranking battery or any other part of my electrical system.

Do you guys think that there is a fault in the switch that is grounding the circuit (boat is 17 years old)h? Maybe some of you have you run across this problem in the past.

Thanks for your help.

Thomas

 

[Silvertip]

Re: trolling motor batteries discharging

Flipping the switch to CHARGE means you need to connect a battery charger to the trolling motor receptacle. The charge position disconnects the series connection and parallels the two batteries so they can be charged with a single 12 volt charger. If you are not doing that, there is a probability that one of the batteries is bad and it is sucking the life out of the other one. The CHARGE position does nothing for you if you don't connect a charger. If you do have a charger connected, they should be charging, not discharging. Please provide a little more detail on how you are using the switch.

 

[FireCapt]

Re: trolling motor batteries discharging

Thanks Silvertip, I will check the batteries for a bad cell. I usually charge the batteries separately by hooking the charger directly to one battery at a time. I was mistakenly under the impression that "charge" meant that the batteries would be topped off while under power. (I've never worked on trolling motors at all). Thanks for setting me straight on that.

If both batteries check out I'll start looking for a short somewhere. And I'll leave that switch off since I don't charge through the plug.

 

[Silvertip]

Re: trolling motor batteries discharging

No - there is no way the engine can fully charge a pair of deeply discharged batteries in just a little bit of run time, especially if you have an older outboard or even a newer outboard in the midrange or smaller HP range. Even high output engines don't have that kind of charging capacity. Although the boat can be set up to charge the batteries, you would need to run for hours at wide open throttle to top them off. When you charge your batteries, set the switch to CHARGE and then you can connect your 12 volt charger to either one of the batteries. Both will charge since they are in parallel. It will take the same amount of time that way as it did charging them individually. When the boat is not in use, set the switch to OFF or leave it in the 24 volt position.