Thread: Minkota Maximizer

The conventional speed control dumps a lot of battery power as heat into the water when it throttles the power down. There is no easy way to reduce the current draw on a DC motor because if you drop the voltage it will draw more current and generate heat in doing so, and if you throttle the current you lose torque.

Imagine that the accelerator on your car is an on/off switch. You can either be off the gas, or floored, but nowhere in between. You control the speed of the car by applying the brakes. No matter how fast you go, you'll get about the same gas mileage. But what if instead of leaving the accelerator on and braking to adjust speed, you begin turning the accelerator on and off rapidly? If you want to go slow, you only leave it on for a short time and off for a longer while. When you want to go faster, you cut down on how long you leave it off. When you want to go wide open you leave it on all the time. Now you can adjust your speed wherever you want it, and since you mostly use gas while you are accelerating, you save some gas when you are going at slower speeds.


Speed coil motors, which are usually 5-speed motors, reduce the motor speed by dumping excess power into the water as heat. When you set the motor to a lower speed, the motor gets less power, but much of the excess power is wasted as heat and the load on the battery at lower speeds is close to what it is at higher speeds. Just like applying the brakes to reduce the speed of the car above.

The maximizer cycles the power to the motor on and off rapidly so the motor runs for short bursts at full voltage and current. You vary the length of the off time when you turn the motor speed control, until at 100% the motor is on all the time. Since the motor only draws current part of the time at lower settings, you don't deplete the battery as fast.

The speed control used in Maximizer or other variable speed motors is known as a pulse width modulator or PWM, because it adjusts the width of the power pulse going to the motor to control the speed.

Identically sized speed-coil motors and a maximizer motors will use the same amount of power when they are set to maximum thrust. It's at thrust levels less than 100% that the PWM saves you power.


That's the good part. The bad part is that the on and off of the current is to an electrical arc in that it contains very high frequency signals in order to make the sudden on and off pulses. If you want the gory details, Google "Fourier Theory". The net result is that rapidly changing currents and voltages in the TM battery cables radiate like radio antenna and can be coupled into other electronics nearby.

Your depthfinders are trying to detect very low power electrical signals while being bombarded by electrical noise from the trolling motor. Setting the motor to 100% will usually stop the interference because it stops the pulsing. You can experience a similar effect by setting a car radio to a dead space on the AM band. Spark plugs are doing a very similar rapid on and off pulsing in the engine, and the radio used to be a good diagnostic tool for finding leaky spark plug wires. A bad plug wire can radiate enough power to block your garage door opener remote signal.

Very well said CatFan.

Very good explanation. Did you type all that or you have a thing to talk into and it types.?

Originally Posted by wilbur

Very good explanation. Did you type all that or you have a thing to talk into and it types.?

Typed it all, then found that one of the TM companies has the very same explanation in their FAQ. I swear I never saw it before. I'll just claim great minds think alike