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Trolling Motor Battery Life: How Long Does It Last?

Mark Armstrong
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It can be important to know how long your trolling motor will last on a single charge as this can affect how long you can stay on the water before you have to return to shore. But there are various factors that may affect your trolling motor battery life including your speed and the type of motor you’re using.

To give you a better idea of how long your motor and battery might last we’ve put this short guide together. We’ll look at amperage hours and draw and give you an idea of how to calculate the runtime for your own motor.

How Long Do Trolling Motor Batteries Last?

Amperage Hour Rating

You’ll usually find the amperage hour (or Ah) rating stated on your battery. This rating is how long the battery will last on a single charge with a consistent output. This means the higher the rating, the longer the battery can power your electronic device, or motor.

The amperage hour rating on the battery does not usually mean it will power your trolling motor for that length of time, as this will depend on your motor and how much power it requires. The rating is generally to calculate the hours if you were to power a motor with a 1 amp draw rate.

Video: Battery Capacity Explained

Some batteries may not state the amp hour rating on them and instead may have a Reserve Capacity (or RC) rating. You can use this rating to work out the amp hours. Divide the RC rating by 2.4 and this should give you the amp hours, which you can then use to work out your runtime using the amperage draw of the motor.

Trolling motor battery guide

Motor Amperage Draw

The motor amperage draw is how much power the motor requires to run. You’ll sometimes find the amp draw stated on the motor. However, this is not always the case and sometimes the amperage draw will need to be calculated from how many watts the motor draws, which can also depend on how many pounds of thrust the motor has.

To find out the amperage draw of your motor, you can divide the wattage of the motor by the voltage. For example, if you have a 348 watt, 12 volt motor, then your amperage draw would be 29 amps.

Knowing the amps drawn from the motor, you can then work out the run time of the motor using the amperage hour rating from your battery. To find this out, you can divide the amps drawn by the motor by the amp hour on the battery. For example, a 50 amp hour battery divided by 20 amps drawn (50/29) equals 1.72 hours, which is about 1 hour and 43 minutes.

This time of 1 hour 43 minutes is basically how long your motor would run at maximum speed in ideal conditions, so it doesn’t necessarily reflect real-world conditions.

To find out how long your trolling motor and battery will last it can be important to know the amp hour rating of the battery and the amperage draw rating of the motor. You can then divide the amp hours (Ah) by the amps drawn to calculate the expected runtime of the motor at top speed in mild conditions.

How Can I Get More Runtime?

Reduce Your Speed

You can increase the runtime of your motor by reducing your speed if you have a variable speed motor. By using a slower speed setting it means your motor doesn’t have to work as hard or pull as much power from your battery, so you can travel for longer on one charge compared to firing along at top speed.

The type of water you boat in will also likely have an effect on your speed and runtime, which is why the runtime calculated from the amp hours and amps drawn is usually for calm, ideal conditions.

In current or rough water, your motor will usually have to work harder to deliver the same speed as in calm conditions. This will likely take more power from the battery, just as driving your car up a steep hill will usually mean you have to put your foot down harder on the accelerator to maintain the same speed as you were doing on a flat road.

Increase Your Battery Power

If you want to get more life from your battery, it can be worth increasing the number of batteries that you use. For example, you could link two batteries so that your motor can run off of two batteries at the same time, which can double your run time.

Video: How to Link Two 12 Volt Batteries 

You could also take a spare battery with you so that you could switch to the new battery when the first one runs out, which can again double your runtime.

Reduce Connected Accessories

If you’re powering other accessories from the same battery that’s powering your trolling motor, it’s likely to affect your motor’s runtime. This is when a separate battery could come in handy, so that you can use one battery for your motor and another to run your fish finder and other gadgets.

Keep Your Battery Charged

It can be a good idea to make sure your battery is fully charged before you use it. It can also be useful to keep it charged even when you’re not using it, for example in winter if you’re not using it, it can be helpful to charge it regularly so that it’s not sitting empty.

Similarly, even if you are using it regularly, it can be beneficial not to let your battery drain completely, as this can affect how well it charges in the future. You may find it helpful to keep an eye on your battery life so that you can recharge or switch batteries before it runs out.


Finishing Off

How long your trolling motor will last will usually depend on the size of battery you use as well as how much power the motor requires. There are other factors that can affect your runtime, such as other electronics and the type of conditions.

So even when you’ve calculated the estimated runtime by dividing the amp hours by the amps drawn it is still likely to be an estimation and not a guaranteed runtime. Have you managed to increase your motor’s runtime with any tricks? Let us know. Share this if you think it might help someone else.


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