I thought I would post some tests I was doing with my Alcohol Injection Systems pump, Hella SS relay and the Haltech Generic Duty output. I tried to be as scientific as a could given the situation. I had found where people had used 30 and 60 hz for the relay, so I started there. I would consider 60 hz to be the best frequency based on the sound of the pump. One item I'm not real sure about is how hot the relay gets when running. There is a reason these relays are basically heat sinks. All pressures varied more at lower duty cycles less at higher duty cycles.

Based on the actual output I would probably jump from 0 to 40 % and vary from there to 100% as the injection system doesn't inject well much lower than that. Voltage was always present even at 0% dutycycle though it was not enough to run the motor. Not sure how that will affect the motor or relay over time.

Anyone have any long term results from use of the Hella SS relay as a coolant motor, cooling fan speed control, WI motor controller?

 

Not yet, but am planning on using one to run gearbox, diff, and elec water pumps in a project shortly, so I find this interesting. Are you able to run higher frequency at all, like 300Hz or anything? I am curious at what frequency the relay looses accurate control. I wold have thought he higher the frequency the smoother the voltage output and it should be kinder on the pumps.
I find it odd that there was voltage present, unless it is a back-feed through the earth circuit or something. Would suck for it to run your battery flat if the car was left sitting is all.

 

Just tried at 120 150 300 hz. Oscillations at partial duty cycles were pretty bad. Relay also heated up very quickly and was too hot to touch. My guess is that it wouldn't make it at those frequencies but who knows.

 

good to know, looks like 60Hz is the goods. I have been wondering if a capacitor on the output might be a good idea. I planned to scope the input and output when I got around to it.

 

Believe the spec sheet for the relay says it's rated for around 45hz, though that's from memory and that is notoriously bad.

 

I was trying to find the spec sheet on the relay without much luck. Hella didn't seem to even have much for it.