Outdoors blog

A 36V trolling motor pull 18 amps at full load. It pulls less at lower speeds.

Amperage or Amperes is the unit in which the strength of an electrical current is determined. Different from voltage, amperage is how much electricity is flowing through the electrical wires in a closed circuit.

For example, your basic iPhone charger uses 1 Ampere to feed your phone battery, the medium-sized MacBook charger uses 1.5 Ampere whereas lightning bolts amperage can go up to 30 000 Amperes. the amperage law is essential knowledge for any electrician or engineer. The current in a closed circuit is measured in Amps.

1. Electric currents

The power formula determines the flow as well as the hardness of the electrical current, the formula that you may see in school books, or while doing personal research is (P = I x V).

By multiplying the amperes (represented by the symbol I) and the voltage (represented by the symbol V) you get the power of the flow; this power’s unit is Watts, so the result you get in measured in Watts.

For example, if a motor’s power is indicated to be 1.34 Watts and we know that it’s powered by a 9 volt battery then we can easily determine its amperage. All we have to do is use the mathematical rule of three to determine the amperage, meaning we divide the wattage of the motor by the battery voltage, which gives us 0.15 Amps.

So now we know that a motor’s amperage value is determined with its voltage and power.

1. What type of trolling motor ?

trolling motor manufacturers like the company Minnkota, almost always provide a data table with their motor’s manual; in trolling boats, the motor’s torque is very important to know because it affects the boat’s speed. If a boat is fully loaded then the torque would increase causing it to be slower than if the boat was empty. The higher the torque the slower the maximum speed, the more battery is used; all of these are essential for maximum efficiency.

When creating an electrical current, it’s very important to be as precise as possible with the measurements of wiring, the power source, the purpose of the circuit for maximum efficiency.

1. What speed are you running ?

The speed of a trolling motor is almost always presented in pounds of thrust. For example, small boats have smaller 12 volt motors therefore they can only do 50 Lbs. of thrust at max. The bigger the boat the bigger the power needed to be efficiently pulled, that’s why bigger bay boats need a 36 volt power source to not only push the boat on the water but also be as efficient as when the boat’s fully loaded.

Similar to force, the torque is a rotational effect that causes a turning force in the motor.

The formula for calculating the torque of a motor is P = T x W where P is the output power measured in watts, T is the torque measured in newton meters and W represents the angular speed measured in radians per second.

This formula is even easier if you know the motor’s rotational speed: W = RPM x 2 π / 60 where W represents the angular speed measured in radians per second; Let’s say that you bought a 36 volt motor that has a rotational speed of 31,100 then and a power of 330 Watts using the power formula, you know that the level of ampere needed:

The motors power is 330 Watts and the voltage is 36 Volt so you can replace these two values in the power formula (P = I x V) and we get 2.4A. meaning that a 36V and 330 Watts motor needs a 2.4 Amps