Notes on the Curtis controllers:

Back in the old days, it must have been 1992, I had a disagreement with Curtis PMC over a warranty claim on a 1221B controller. As a direct result of that I decided to repair the unit myself. (I later found out that it really should have been fixed under warranty. From what I've heard customer service may not be their strong point, especially with Greg Wherely who is long gone I'm sure) In the process of rebuilding it I reverse engineered a schematic of the one that I had. Thus began my education in controller design. Thanks Curtis, without you I'd probably have a real job that actually pays. :-)

I took my new knowledge of how the controller worked and used it to convert a 1221B to operate in regen mode. Home Power published my article on this project over the objections of Curtis PMC. Over time it became clear that the controller had enough trouble surviving without regen and getting a motor to tolerate regen without seriously shortenting its life was daunting. I rebuilt that one twice before giving up on the 1221 altogether. Here is the article for those who are curious: Regen Article. But I really don't suggest doing this.

Years ago I gave Rich Rudman a copy of the schematic, he redrew it in OrCad and made it better, but there are still many errors carried over. Beware when you use it. I started to fix it but since OrCad is not my native system I am posting it as is. Schematic in pdf

If you are good with OrCad you welcome to fix it up, I'll post the improvements here. Orcad 7.2 schematic here.

Richard Bebbington was kind enough to send me a pdf copy of the Curtis controller owners manual. It has an excellent functional diagram on page 48.
I've posted it here: Manual in pdf.

Wondering why so many of the controllers failed? Aside from moisture intrusion the "B" models had current limit issues with low resistance motors. Lee Hart wrote a wonderful piece about it, you can read it here: Click here

Just so you don't ask. No, I don't repair Curtis controllers. I have no affiliation or financial interest with the company. I am just providing this information to satisfy the curiosity of others. I hope you found it interesting or useful.

If you are wanting to build or modify electronics for electric vehicles, the best place to listen learn and ask questions is on the EvTech list which Sheer is generously hosting. You can subscribe to it here: