For those of us that have 24v trolling motors for the fishing boat, the hardest problem at the end of the day is how to charge the 24-volt system.
Usually, these small electric propellor motors are wired up to two 12v car or marine batteries. These are wired in series to provide 24 volts to the electric outboard motor.
The simple way to charge the batteries up is to use a dedicated charge controller that will either output 24v to both batteries or 12v to each battery.
We will cover the pros and cons of each setup, and what you will need to keep your deep cycle batteries in tip-top condition. That way next time you go fishing your batteries are fully charged
Table of Contents
- 1 24-volt trolling motor wiring with charger
- 2 How to charge multiple batteries with one charger
- 3 Can you charge a 24v battery with 12v solar panel?
- 4 How to run 12v off 24v system?
- 5 How long will a 24v trolling motor last?
- 6 Conclusion
24-volt trolling motor wiring with charger
Permanently mounted charge systems for trolling motors are the way to go. You just need to plug them in at home for a few hours and you are ready for the next trip.
I use a NOCO Genius GENPRO 10×2, 2-Bank, 20-Amp (10-Amp Per Bank) smart charger. This thing is small and waterproof. The good thing about this setup is that it will charge each battery fully and balance them. It is how I charge my 24-volt system trolling motor batteries.
Each output from the NOCO genius will go to each battery. So if you have a 2 battery setup get the 2 output model. If you have 3 batteries get the 3 output model.
I like these waterproof onboard boat chargers because they are a Battery Maintainer and Desulfator for AGM, Lithium (LiFePO4), and Deep-Cycle Batteries. One charger to do them all.
24-volt charging system diagram
How to charge multiple batteries with one charger
Trolling motor batteries are usually 2x 12v batteries wired in series. This makes it hard to charge multiple batteries with one charger. If you charge both batteries in series with a 24v charger they could become unbalanced over time unless you use a smart charger like NoCo Genius.
There are smart chargers that have sensors to charge 2, 3, and 4, 12v battery banks. Another way is to charge each battery individually.
Unless you have a dedicated 24v battery charger you will need to use a 12v smart charger. This means you will be charging one 12v battery at a time.
It is best to disconnect the series lead between the two batteries to prevent any polarity issues. The series lead is marked in green in the above image.
NoCo makes this fully automatic 2 battery smart marine charger that you can leave connected to your 2x 12v batteries. It connects to 110v AC so that you can charge both your batteries with just one charger at home. There is then no need to disconnect the series cable. I like that it is rated at 20A so it’s 10A per battery for a dual battery setup. So its fast.
There are DC battery chargers that use your boat’s outboard engine to output 12v to a battery charger. In reality, the output to charge multiple batteries is just not viable. The amp rating of the alternator is just too low for any extra charge capacity.
For more information check out the video below on how to Charge a 24V battery bank from a 12V boat alternator.
Can you charge a 24v battery with 12v solar panel?
Yes, but you will need to have a 12/24v solar charge controller. They are becoming quite popular as many people run 12v and 24v systems now for trucks, and boats such as trolling motors.
If you do use a 12 to 24 v solar charge controller make sure that you weatherproof it if you are using it for trolling motors in a boat. The wet weather, sea salt, and UV rays will damage these charge controllers fast.
Solar is a cheap way how to charge a 24-volt system trolling motor batteries while out on the water or in a remote location.
How to run 12v off 24v system?
If you have a 24v system made up of 2x 12v batteries, then it is straightforward to run 12v by connecting your power leads directly to only one battery. If charging 24v then connect to both batteries.
As the batteries are in series you can safely tap off 12v from one of the batteries. Be sure to use an inline fuse and a battery isolator so you can disconnect the power if required.
If you only have one 24v battery then you will have to use a 24v to 12v transformer to step down the voltage.
Using 12v on 24v system
Be sure to not exceed the amp rating of either the step-down transformer or the inline fuse from your battery. Also, you will need a way to charge up the battery that you are draining from. Solar and electrical battery chargers will work well for a single battery.
How long will a 24v trolling motor last?
Now this will depend on many factors such as maintenance, speed, brush or brushless, salt or fresh water, and quality of the materials used.
Sun and salt will destroy these motors fast. Always wash them down after use and store them away from full sunlight.
12v vs 24v trolling motor run time
There are a lot of variables to consider before we work out the run time on a 12v vs 24v trolling motor.
- Size and capacity of the 24v batteries.
- Size and amp rating of the trolling motor.
- Thrust power of the motor.
- Speed of the trolling motor.
- Are you running any other electrical devices off the 24v batteries such as navigation lights, bilge pumps, starter motors, or depth sounders?
The below table shows how long trolling motors will run at different speeds and motor sizes using a 100A battery.
A 24v trolling motor will have more power than a 12v system. But the setup cost will be more as you need 2x batteries and extra electrical cables.
To keep trolling motor batteries at peak condition always charge them after use. This will prevent sulfation and low capacity. I like to replace my trolling batteries every 4 years to make sure they can deliver peak power when needed.
If you have the ability to trickle charge your boat batteries while out in the water via solar or an alternator then do it. Never drain your batteries to under 11.5v per battery.
I like to use a 12-48v battery capacity LCD display for my 24v trolling motor batteries. It is easy to wire up and gives me a quick indication of the capacity left in my bass boat.
Hopefully, you have now learned how to charge 24-volt system trolling motor batteries the correct way.
Always have a backup solution for your trolling motor if you run out of power. Be safe and maybe I will see you out in the water one day.
I am a qualified Industrial Electrician for the past 20 years and I love to share my knowledge on home repair and maintenance jobs.
I love fast toys like Motorcycles, Cars, Jetskis, Boats, and Computers so writing about them is easy. Working on them is fun.
To keeps costs down I do all my own mods, repairs, and servicing. These skills I want to share with everyone. DIY is a skill everyone can learn.