Trolling Motor Battery Rigging

First off, I want to thank everyone who responded to my question last week on trolling motors. I have decided I am going to get one, either a Motorguide that puts out 82# of thrust or the Minn Kota that puts out 74#.

I will need a 24V battery system to power either choice. Similar to the post below, I have some questions on batteries, but more about rigging them up. Sad to say, I am an electrical engineer, though that doesn’t mean much. An on-going family joke revolves around my multiple college degrees and my apparent inability to wire a three-way light switch! Seriously, though, its not quite that bad. Some of the projects I start do actually end up working.

Back to the batteries. I have a 12V system right now on my boat. I need 24V. The way I see it, I have several options:

1. Add one more battery in series and run the trolling motor off the totem pole of two.

Concern: Economical, as I am only buying one battery in this case; but my present battery is a starting battery, when I should probably be using a deep-cycle. Is it a bad idea to use the a starting battery and a deep-cycle in series together, is mixing and matching a no-no?

2. Buy two deep cycle batteries, making sure each has a enough cranking amps to turn over my engine and donate my brand new interstate starting battery to the needy; still just 2 batteries.

Concern: Is starting the engine hard on the deep cycle batteries? This involves buying two new batteries, but they will be “matched”. I would rig this up as a series totem pole like the first option.

3. Keep the cranking battery and 12V side of the house as is and buy a bank of two deep cycle batteries and wire the trolling motor separately. Independent 12V and 24V power busses.

Concern: Now I have three batteries instead of one or two. I would only have room for one six gallon gas tank instead of 2. That kinda sucks, but so far, my Evinrude etec has been pretty easy on the fuel. There’s only so much room in my aft compartment!

So, if anyone has gone through this before and figured it all out, let me know your opinions. I appreciate your advice and interest.

Regards,

Joe Jiacinto

I have a suggestion. From what you said about your gas tanks, I take that to mean you have a smaller boat. 74# is overkill on a small boat. While its true that batteries last longer with a 24v motor, a smaller boat requires less thrust which you can get out of a 12v motor. Then you can get by with one Deep Cycle and one Starting battery. Buy the largest battery available and it should last you all day. I would also suggest buying a quality deep cycle charger. If you decide to go with the 24v system I would strongly recommend buying 2 deep cycle batts and keep your starting batt also. Hope this helps. Good Luck

Steve G

I have been using two deep cycle batteries (option 2) for 12 years with no problems. The big motor then charges one of the batteries when going between spots. If your big motor is over 100 hp, or is hard starting, then you may want to get a separate battery just for starting.

I also buy Fleet Farm batteries and use a cheap 10-amp auto charger. When I get back from a fishing trip the battery hooked to the big motor is usually 100% charged, and the other trolling battery is about 60% charged. My batteries last about 5 years and I use the electric trolling motor a lot.

I have a 70 hp tiller and keep both batteries in the mid/front of the boat. I use a 24-volt transom electric trolling motor which uses more energy than a bow mount because I pull the boat backwards when vertical jigging in the river.

Dave Gulczinski

Steve makes a good point, what type of boat are you adding the system to?
If you are going with a 24 volt system get two deep cycle batteries. Keep your cranking battery for just that purpose. You do not want to put a cranking battery in service with a trolling battery. If you are going to run a bow mount trolling motor is there room up front for your batteries? Most time this will help with weight balance in the boat.

Thanks for the opinions guys. Let me tell you a little about my boat.

The boat is not quite a “jonboat” in the traditional sense, nor is it really a full blown “bass” boat either. I bought a Lowe roughneck, model 1860VPT. It is 18′, has a semi-vee hull fore and a very shallow (almost flat) vee in the stern. The transom is 20″ high. I got it to serve the dual purpose as a fishing boat and waterfowling rig, and so far have been very pleased with its ride in rough water and the stability. It weighs 690# empty.

I plan to put a pedstal seat on the front casting deck and place the trolling motor up there as well. There is already a plug and mounting plate for a trolling motor, its just not wired up. My main engine is a 50 HP Evinrude etec. Steering and throttle is via a side console. I liked the side console because it left a very open deck when fall duck hunting time comes around.

I figured I would go with at least 70#-80# of thrust because I plan to fish mostly in the river and felt more thrust might come in handy in the faster currents and rips. There is a compartment up front where I have been storing my rigging and life vests, but I suppose I might be able to store a bank of batteries in there for the trolling motor. Lots of folks say to keep the weight in the back, but we already have one battery, fuel, and the main engine back there, so maybe placing two batteries up front might be OK.

I hope this gives you guys a better idea of my set-up, and thanks for the ideas and interest.

Regards,

Joe Jiacinto

I’d be concerned with the weight of two batteries. I’d go with a 12 volt trolling motor. Your rig is light and doesn’t have a lot of exposed sides to catch wind. I don’t think you need the day and day out power of a 24 volt.

If you insist on a 24 volt. Get two new identical 24 series batteries to save size and a little weight.

Don’t rig a 12 volter to the starting battery. Just asking for trouble. Do you know how to start the engine with the emergency cord?

Yep. I keep a piece of spare 1/4″ rope just for that purpose.

Regards,

Joe Jiacinto

Kevin, I think your question should have been “Do you like starting your motor with the cord?”

I hear you guys loud and clear. No, I would prefer to not use the emergency cord!

I spoke to some fellas at work and they pretty much felt the same way, basically rigging the trolling motor system separate from everything else.

Now, I just have to figure out if I really need all that thrust from a 24V system or if 54# thrust 12V will be enough.

Thanks,

Joe Jiacinto

Mr K. King, that is the question of the day.

I have the bow mount Minnkota 55 on my 17.2 Lund Angler SS. I don’t recall the weight of my boat, but I think it’s heavier than yours. If I was to do it over again, I would go with a 65 or better, which puts me in the 24 v group.

That’s more of a want than a need. The only time in 2 years that I felt I NEEDed something bigger was out in the open on the Croix with gusts up to 35 mph. I switched to the 90 hp for trolling that day. But again, with motors and boats…bigger is always better….

Hope that helps…a little.

PS..not to beat a dead horse, but last year my starter battery was starting to go. I notice it was taking a little longer to charge (although I normally didn’t put it on the charger..the motor would normally charge this for me) Well, I was trolling around on day playing my favorite CD…Meat Loaf…Bat out of Hell and figured it was time to go home…Nothing, the CD player robbed me of enough power to start the big one…So I trolled home with the electric. If I was king…all boats would come with two batteries – one only for starting only and the other for radio, sonar…wide screen HD TV, blender, refregerator and the expresso maker for my wife…

I just went through this. My question is when charging do you need to unhook the two batteries? If they are connected does the charge charge both batteries or only one at a time. I went with two batteries independent with my bow mount and another deep cell for everything else.

Before I installed an on board charger I had better luck charging the batteries independently. You may want to check into a 3 bank on board charging system.

I guess I don’t have anything to compare it to. I have a 10 amp “smart” charger and charge both batteries at the same time. If you have a three bank charger, (all 10 amps) it makes sense that it would charge the batteries faster…

But Don, do you have two of the banks (at 10 amps each) connected to the two trolling batteries?

Brian, I have 4 batteries in my boat. I have 2 Guest chargers both are two bank. At the time no company made a four bank. Yes each battery has its own bank.