Speed controller trouble


New Member
Local time
3:48 PM
May 8, 2024
Anderson, Indiana
I have a tadpole trike I built and added an electric hub kit I bought several years ago. I have no record of that purchase now, so I don't know the brand. I'm pretty sure I bought it on Ebay.

It's a 36V 500W.

I had been using three 12V sealed lead acid batteries wired in series to run it with no problems whatsoever.

This year I bought a 36V 30Ah lithium battery on Amazon that was shipped from China.

I wired it up. I'm sure I wired it correctly. I rode somewhere about 3 blocks and the controller went dead. Turning the power switch on and off didn't help. The battery measured 37.2V

Then I bought a new controller. 36V 500W square wave. I wired it up and rode it around the block a couple of times, everything was fine.

Then I got a SPDT toggle switch to hook up the 3 speeds. Rode it in second (default), released the throttle and switched to low, that worked. Then I released throttle and tried high. Shortly after that, the controller died. Both times, it happened at full throttle. Battery voltage is 37V

The battery's maximum discharge rate is 25 amps. The new controller is rated 25 amps.

Does anyone have any ideas what the problem could be?

Would it be possible to get a 750W controller or do they have to be matched to the motor?

Is there a problem changing between square and sine wave controllers?

I only have two good lead acid batteries now, so it wouldn't be easy to swap back to those.

I'll really appreciate any advice I am given.
2 Darwins now, you guys are mincemeat now..........only thing I can add to your post is that you need a different charger for lithium ion batts vs lead acid. Someone correct me if I'm wrong here. I know on m/c batts you need a charger designed for lith ion batteries vs lead acid.
The lithium battery came with a charger.

I'll bet I've been a "Darwin" longer than you. 69 years

I have been thinking about it and wonder if it could be the throttle.

Looking at my old one, all I see is capacitors, a couple of resistors and whatever the things are that handle the power - they look like voltage regulators, but I know that isn't what they are. MOSFETs?

I'm a bit familiar with brushless motors via multirotor drones. This is a whole different thing, though