Charging Batteries - Trolling and Engine

[MI Boater 65]

1st post and I apologize if this was covered in another post, but I wasn't able to find the info. I was looking for the following information: I have a fishing boat with a 115 Optimax and a 55# thrust Minn Kota trolling motor. Trolling motor is a 12 volt system and the boat is setup for 2 batteries, currently I am only using one battery. I'm trying to determine how many banks I need and what amperage. I may down the road add the 2nd trolling motor battery.

Are the 2 batteries (currently 1 spot open) for the trolling motor wired in parallel such that 1 bank would take care of both? Or are they wired separately to the trolling motor such that I would need a bank for each battery? I'm assuming they are separate such that the empty battery cables wouldn't have power. So I think I would need a bank for both. If that is the case are there chargers that would accommodate having a bank but the battery isn't currently installed? I understand the amperage options affect the charging time to recoup the battery.

Is it worth having a bank dedicated to the boat? If so, what type of amperage rating for the charger would be recommended? I've never had an issue with the motor not wanting to start and I sometimes run the radio and fish finder while the main engine is stopped.

I appreciate any feedback on my questions and suggestions for what type of charger that would fit my needs.

 

[UncleWillie]

A few questions need to be answered.
Does the trolling motor currently operate with single battery? Or, is this a new addition?

You will need to determine where the unused battery cables connect to. Battery Switch?
I would hope that they are unconnected or that Red wire posses a real danger.
Measure the voltage on the detached cables. Zero?

Normally the starting battery and the trolling battery operate their separate systems in isolation.
Having the Trolling motor kill the starting battery results in a bad day.
The starting battery will be recharged by the alternator.
The trolling battery is recharged by a shore powered charger.
A two bank charger can be installed and is nice but not required.
If one bank of the two is unused/disconnected at times, it is not a problem.

 

[Silvertip]

You have a 12 volt motor so using two batteries has a couple of options.
1) Wiring batteries in parallel will double the run time but voltage remains 12 volts.
2) Parallel wiring is done at the batteries -- not the motor.
3) You can charge both batteries with a single bank charger but you should have a 10 amp charger or larger.

Option #2 is to continue to use two batteries but run the motor off of just one of them until it is depleted and then switch to the other. Run time is basically the same as if they were connected in parallel and you eliminate the possibility of the weaker battery sucking down the stronger battery. Selection of which battery you use can be done with a dual battery switch, or simply do it manually with alligator clips on the troller wires. A single bank charger of 5 or six amps would work here but the batteries would be charged individually if you are using alligator clips to switch between batteries. A larger single bank charger would be used if using a dual battery switch. You set the switch to BOTH and connect the charger positive lead to the COM TERMINAL on the switch.

 

[MI Boater 65]

I finally was able to get my boat out of storage. The two sets of leads from the battery trays to the trolling motor receptacle is setup for one 12V battery or two 12V batteries in series for a 24V trolling motor. The mating plug of the trolling motor will determine if it is 12V or 24v. I have a 12V trolling motor, so if I want to use two batteries then I will need to wire the 2nd battery in parallel to 1st battery as Silvertip suggested. I also like the suggestion of having a switch to prevent a weaker battery discharging the other.

The 2nd set of battery leads are not hot since they are wired for a 24v system and I'm using a 12V so not issues there.

Any suggestions on if it is worth having another bank for the main boat motor battery? I see some chargers have a 3 or 5A bank for that purpose.

Thanks for the help.

 

[MI Boater 65]

Any recommendation on a switch or a kit for adding a 2nd parallel battery for the trolling motor?

 

[poconojoe]

I would keep a separate battery for starting the engine. You don't want to get stranded. You can also use an ACR (automatic charging relay). Look them up. The ACR will charge only the battery that needs a charge. And they can be used with a battery charger or the engine charging circuit. Blue sea makes the one I have. I have mine set up with a perko switch that has 1-2-all-off. I have two batteries. Before I had the ACR I had to switch the perko to the weaker battery to charge it. Now the ACR does it automatically.

 

[MI Boater 65]

I do have a separate starting battery for the main motor which is isolated from the trolling motor battery. I have a battery tender with a quick connect plug so that I can connect to the charger and maintain the starting battery when the boat is not in use. What I was talking about above, is to add a 2nd trolling motor battery. I think I will use the perko switch or something equivalent and then an onboard 1 bank charger which I will connect to battery 1. When I want to charge both batteries, I can switch to both on the perko.