Fan Speed Control

ajriding wrote:
No, just two issues that really matter.
1. Wasting electricity on the heating element-looking thing (wasting time talking about whether it is a heating element or a resistor), and
2. what controller is most efficient.

Heating up a coil might be a small amount of power in your mind, but do that all night long using a battery that is powering other things might just be enough to run the battery too low after a few cloudy days in a row. Run the battery too low and you got bigger problems than unrelated post.
It's all about the battery. Not everyone understands this. I know some people hop campground hook-up to campground hook-up, but others require everything from a battery set-up.

Instead of guessing, one day I might wire in an amp meter and actually measure the difference between High speed (no resistor), Medium and Low speed.
Eventually someone on forum will have already done this. I appreciate the guess on how much power the settings might use.

Your not going to "save" enough energy wasted by changing to PWM to noticeably increase the time between battery charges or shortening the time it takes to charge the battery.. We are talking maybe minutes at best per day.

PWM controller will eat up a lot of your "savings" in wasted power depending on the "speed" you want the fan to run.

At "full on" your PWM controller will be ADDING it's conversion losses to the wasted energy of the fan motor causing you to actually use more battery than if no PWM was connected.

The fan motor you are using is highly inefficient to start with, it will be a brush type "can" motor with a simple sleeve bearing. Basically late 1890's DC motor design, there is nothing efficient with that motor..

PWMs also have another narly side effect, NOISE. Most cheaply designed PWMs do not filter the output, this results in your motor windings giving off a vibration which depending on frequency may be in your hearing range and may sound like a whistle. Unfiltered PWMs will also have considerable switching harmonics, those harmonics are not "usable" energy and result in your motor burning up as wasted energy rather than constructive usable energy.

The brush motor also can cause considerable issues with backfeeding the PWM controller with brush noise and inductive spikes full of harmonics out of phase with the PWM.. PWM controller may not like that and I suspect that is why yours burned up on you..

If you really want to reduce your battery useage, you would need to hop up to basically a brushless motor like what is used in computers. Those are far more efficient energy wise than a brush type can motor.

Don't get me wrong, PWM under the right use and correctly done can save a couple of watts of lost power, but in the case of small motors, not much savings to be had to make this endeavor worth it.

Try a computer fan, bet it will move as much air or more at half the wattage than the motor you have now.