If you are wondering how long your electric trolling motor will last, then you need to know about your motor amps .i.e.
- How many amp hours does your battery support?
- What is your amperage draw?
These questions are similar to how you discuss your car issues, such as what gas mileage does it get or what is the capacity of its gas tank. Let’s start with a car battery’s example to solidify your understanding of the trolling motor’s battery.
How The Battery Works
The function of a battery is clear to anyone who is a boat hobbyist, but not everyone knows how it operates when it comes to different types. The motor battery is used to store and hold energy for use.
The batteries used in cars are known as lead-acid batteries – comprising lead plates that are submerged in acid. Usually, these batteries fall in the category of floating batteries, where the acid acts as a liquid that can flow easily within the battery casing.
Often, people don’t recognize that there are multiple types of car batteries. However, this fact is overlooked due to their similarity in looks.
Next, let’s learn about the battery measurements, including cranking amps and amps hours. Cranking amps (CAs) is the amount of amps delivered by a battery in 30 seconds at 32 degrees Fahrenheit.
Cranking cold amps (CCA) are similar, but they are recorded at 0 degrees Fahrenheit. CAs work best when it comes to short bursts of intense usage like starter motors.
Amp-hours refer to the number of amps delivered for a fixed number of hours. For instance, a 100 amp hour battery consumes 1 amp to deliver 100 hours, or 20 amps to deliver 5 hours. The formula is simple:
Amp x Hours = Amp Hours
You’ll also notice RC or Reserve Capacity in place of amp-hours in some batteries. RC represents the number of minutes a fully-charged battery delivers in around 10.5 volts at 80 degrees Fahrenheit while drawing 20 amps.
You can convert RC to amp hours by using the following formula.
Amp Hours = RC/2.4
Car batteries have lead plates that contain multiple drilled holes. This design aims to increase surface contact with the acid to generate maximum energy in a short period of time.
However, this also depletes the battery rapidly. Cranking amps are used to measure the power of car batteries. They are ideal for applications that need short bursts of power.
Deep cycle batteries contain solid plates. This is why they last longer and are more stable. Amp-hours or RC ratings are used to measure these batteries.
They are mostly used for applications that require a steady power draw – motors in wheelchairs, golf carts, and electric trolling motors.
Marine batteries are generally a hybrid between both types of batteries. These plates contain few holes, but not as much as car batteries. They are used to start your motor with CA and offer support for a steady current draw for uses like electric downriggers.
Usually, these batteries are not used with trolling motors, particularly for extended periods. In most cases, they are measured in terms of CA or CC, whereas Amp Hours and RC are also used once in a while.
Keep in mind, battery labeling isn’t always representative of a strict standard. Hence, read the numbers carefully while you are choosing a battery. Keep in mind that batteries come in different sizes. Therefore, it should fit where you place it.
In the case of trolling motors, it’s better to go ahead with a deep cycle battery due to the higher number of amp-hours or RC, thus ensuring that your motor will run longer.
After some time, your battery starts to wear out. It can happen due to over-discharge, poor maintenance, or simply age, and your battery fails to deliver the expected amp hours.
You also need to know about the motor amperage draw. It is a rating that tells you how much current or amps a motor draws at a particular speed. It’s tricky to find the exact amp draw rating of a motor, but you can get in touch with the manufacturer or send us a message to learn about it.
To calculate how long a motor can run on the water, you have to take your battery’s amp hour rating and divide it by the amp draw. For instance, if a motor delivers 30 amps at medium speed with a 100-hour battery, your run time is most probably around 3.3 hours.
Manufacturers usually list your trolling motor’s max amperage draw at startup and on top speed. Therefore, you need to use it as a baseline to estimate draws at other speeds.
How Long Will Your Motor Run?
Let’s consider that you have a deep cycle battery, which has an RC rating of 150. As specified above, divide it by 2.4. This means that your battery has 62.5 amp-hours.
Suppose you are using an electric trolling motor by Minn Kota 50 pound thrust at a speed setting of 2 and it’s drawing out 20 amps. Using the complete battery is detrimental to its health, so you can try to use 50% of it. In this way, you have around 1.5 remaining hours as per the following calculation.
62.5 * 0.50 /20 = 1.56 hours
Do note that this is the max runtime – it’s unlikely that your motor runs constantly for 1.56 hours.
If your battery is also used by electric downriggers or fish finder, it will also cut the power delivered to your electric motor.
Keep in mind that weather and water can have a substantial impact on your battery’s performance. A motor that requires 10 amps to move your boat at medium speed in stable weather may require 20 amps for moving the same boat in stronger winds. Therefore, if you are going to use your motor frequently in stormy or windy conditions, you need to keep these factors in mind.
Larger trolling motors offer the same thrust as smaller motors while drawing fewer amps. It helps to increase your run time. If you want your boat to run for extended periods, it’s a good idea to purchase a 24v motor, such as the 24v Minn Kota.
Hopefully, this article helped you to gain an understanding of how many amps a trolling motor uses. Get in touch with us if you have any more questions regarding trolling motors.