# two 12 volts to run a 24 volt trolling motor



## jshbuckeye

Anyone have a diagram of how to wire up two 12 volt batteries to run a 24 volt trolling motor. How bad is it to run a 24 volt motor on a single 12 volt battery. Next question can you buy a 24 volt deep cycle battery? Thanks in advance for any and all info. Jeff
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## Marshall

I did a search for ya and found this: It came from a member named steelmagoo. Thanks for the input steel.

Parallel means connect the batteries pos to pos, neg to neg. With two 12V batteries in parallel you get 12V if you put a meter from any neg to any pos. 

Series means pos of battery 1 to neg of battery 2. With two 12V batteries in series you get 24V across pos of battery 2 to neg of battery 1.


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## leeabu

One of the worst this you can do, short of filling it with water, is to run an electric motor at a reduced voltage. You will burn up the windings in very short time. Hook the + of one battery to the - of the second battery with a short lenght of 8 quage wire. Now hook your motor to the remaining + and - terminals of both batteries. An inline circuit breaker of sufficient amperage for your motor is always a good idea.


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## jshbuckeye

thanks guys this confirms what i have been hearing but found it hard to trust putting a positve to a negative then hooking your trolling motor wires to the two remaining terminals positive to positve and neg to neg. Goes against everything i ever thought but i am no electrician by any stretch of the imagination. Thanks and im saving the diagram.
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## EE

another question........what if you have 3 batteries? would it harm a 24 volt trolling motor to have 3 batteries in series? If you have a 24 volt trolling motor and 3 12 volt batteries in series, there are 36 volts to draw from, but I'm assuming the motor will still only draw 24 volts since that's all it needs. 

I'm looking at this from the perspective of extra time on the water........it would seem 3 charged batteries it would last longer than 2


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## Fish4Fun

> another question........what if you have 3 batteries? would it harm a 24 volt trolling motor to have 3 batteries in series? If you have a 24 volt trolling motor and 3 12 volt batteries in series, there are 36 volts to draw from, but I'm assuming the motor will still only draw 24 volts since that's all it needs.





> Parallel means connect the batteries pos to pos, neg to neg. With two 12V batteries in parallel you get 12V if you put a meter from any neg to any pos.


You can put 3 batteries in parallel and you will still only have 12 volts just more amps to last longer. But if you put 3 batteries in series you now have 36 volts and your motor requires 24 volts there are trolling motors that run off 36 volts but not good to run your 24 off of that. Over voltage just as bad as under voltage.


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## peon

id suggest running the 2 batterys in a series and putting the 3rd onto one of them in a parallel


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## leeabu

peon said:


> id suggest running the 2 batterys in a series and putting the 3rd onto one of them in a parallel


You will get little to no advantage to doing this. Best to reduce your boat weith by not carrying the third battery. Or what I do is run a 24 volt on the back and a 12 volt on the front and put the third battery in the front of the boat for shorter wires to the front motor.


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## Saildog

A few basic tips on batteries and electrical devices:

1) Think of electricity like water. The amperage is the flow and the voltage is the size of the pipe. The higher the voltage, the more efficient the system and the smaller the wires can be (for a same power output). 

2) Always run a motor as close to optimal voltage as possible. More is not better. Less is just as bad.

3) Batteries in series act like coil springs in parallel. 

4) Power = Voltage X Amperage. That 100 watt bulb in your house uses about .9 amps. 

5) When wiring batteries (especially marine or automotive) in parallel, ALWAYS use two batteries of the same size and condition. NEVER put in just one new one! The older battery will quickly draw down the new battery and shorten it's life. The effects are not as severe when dealing with batteries wired in series (24v). 

6) Setting a battery on concrete will not effect it's life or charge. That is myth. The plastic casing doesn't care what it's put on.


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## steelmagoo

I like to think of it this way: electrical voltage is analogous to water pressure and amperage is analogous to water flow. It takes twice as much flow at half the pressure to get equal energy.


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## Jason6644

Set up your 24volt system for your trolling motor and trolling motor only. Then use the other 12volt battery to run equiptment such as bilge, lights, depthfinder, and anything else that runs off of 12volts.

J


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## papaperch

Amps is what is drawn, volts is pressure. Ohms law states E= I X R Voltage ( E ) is equal to Amps times Resistance in a simple DC circuit. If your motor is designed for 24 volts use that voltage ONLY. Your resistance is the motors load. So if your motors drawing 6 amps at full speed your resistive load is 4 ohms.

Wattage in a dc circuit is P= I X E Power ( P ) is equal to amps ( I ) times voltage so in the example above you would be using 144 Watts. 
At full speed going back to example you hook a 12 volt battery in place of a 24 volt battery. Load would be 4 ohms so amperage would be 3 amps. Your wattage would decrease 36 watts. Wattage is energy so by cutting your voltage in 1/2 your motor is now 1/4 of desired energy. Performance would be abysmal. Assuming 4 mph is your top speed when running 24 volt your top speed now would be 1 mph at 12 volt.


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