Motor cutting out on custom Ebike

[pstrick2]

I purchased an old E-Moto ebike that was missing the battery.

I replaced the controller with a 36V controller and bought a 36v bottle battery off ebay.
The original controller ran at 24V, but I am over volting it.

Here's the problem:
After trying to climb a steep hill (Full throttle and pedaling as hard as I can), the motor just stops giving me any power.
Sometimes it will come back right away if I release the throttle and re-engage it. Other times, it will only give me a 1-2 second spurt before dying again. These issues continue even once I'm on level ground.
If I let the bike sit for a while, it will usually be fine again.

I know I am putting too much strain on the motor. My plan is to ride it until the motor dies, then replace the motor.

What is causing my issue?
1. Battery. I have an LED display that stays lit throughout all of this. In fact, the LEDs jump up to indicate a full battery as soon as the motor cuts out. (This is typical of the cheap display. When under load, it has 2 LEDs. At rest, all 4 light up.)

2. Controller. I don't have fuses anywhere yet and could be hitting a thermal cutoff. The display is driven by the controller, though, which never turns off.

3. Motor. Is over-volting a decade old motor on a steep hill just too much for it?

 

[Voltron]

That almost sounds more like a weak battery cutting out. It also could be thermal protection in the controller kicking in, if it happens right at the bottom of a hill, maybe it's battery cutout as the load hits, as the heat wouldn't have time to build up.
The voltage bouncing back up, esp on what should be a charged up battery indicates it's sagging a lot under load?
I guess if the display is staying on though, maybe that isn't it.


Either way, it probably isn't the motor, not with the cutting out and coming back on later.

Does it get worse if the battery is only half charged when you try a hill? If it's the same regardless of battery state, then maybe it is thermal.

 

[pstrick2]

I can usually get most of the way up the hill before it cuts out. If I walk the bike up the hill instead of riding, I have no trouble at all for the rest of my commute.

My commute is uphill on the way in and downhill on the way home. On my way home today, I will turn around at the bottom of the big hill (the one that gives me problems) and see how far up I can make it. Since I don't charge my bike during the day, the battery will be somewhat more discharged than it was this morning.

 

[Voltron]

I test rode an Emotion that did that, the customer swore it would cut out after a while, the other mechanics swore she was imagining it, but finally took it for a nice long ride with hills, and it did pretty much what you described when it finally got to the magic temperature.

Do you have the replacement controller in the original Emoto box, or a bag, or is it mounted out in some airflow?

 

[pstrick2]

I made a custom wooden box that sits just above where the original controller sat.
To keep it waterproof, I didn't drill any vent holes...

I'll post a picture this evening of how I set it up.

 

[larsb]

That’s it then, probably controller overheating. Some airflow over it or mount it to a cooling flange going to the outside of your box would help.

There’s still the possibility that the hill is just too steep for the current output needed though.