can regen damage your hub motor?

can regen kill your hub motor?

As long as it doesn't get too hot, I don't see how it could hurt it.

No, but you can fry your controller Mine did on a 2 mile downhill the other day using it all the way. What can I say, it was steep and I didn't feel like going fast....

Yeah for sure if I was using it on the regular I'd want to ensure proper controller cooling (i.e. not in a bag), and ideally some way to monitor it's temperature.

Maybe a high temp light/alarm as opposed to just having it disengage regen, which could be a safety issue.

Yes, if the regen causes the axle to work its way loose from dropouts with too much play and no threadlocker / loose nuts.

Regen could also damage your motor if you are running close to your thermal limit without regen, then add aggressive regen to the same load and toast it.

I had heating issues with my setup so dialed the regen down to a pretty low level. It still helps a lot with braking but things don't get so hot. I also had evidence of the axle twisting a little as the torque arms are slightly dented where the axle contacts them.
So a little is good but a lot needs to be designed for.

Running CA3 the default Reg came on hard enough to back off my nuts. Played with the setting for a while to get it to come on soft but enough to slow me down and with the variable it works great and saving my break pads for complete stops.

I am planning a very heavy utility / cargo / tandem rig, and want to maximize regen while also getting a robust "drag braking" capability for safety and control on long / steep descents rather than wearing through brakepads.

Problem arises once the bank gets up to Full, right?

Is there a way to use those big aluminum wire-wound power resistors + heatsink mounted in the slipstream airflow? Or hollow ceramics, but maybe fragile?

Also used for CC discharge load testing big battery banks at 1000+ watts, get up well over 500°F. 

The heating problem is that if you run the motor as a motor it heats it up. Then if you run it as a generator, that also makes heat.

Makes cooling the thing down hard, if you just almost melted the motor on the way up.

So like lots of questions, the answer is it depends. Regen won't fry your motor if you didn't get so hot going up that hill. Mainly this would be a problem if the hill is a mountain, where you top out really hot.

For my touring bikes, I liked using a lower rpm DD motor. This made it resist going much faster than 30 mph, on grades up to about 6%. So coming down a mountain heavily loaded, I only needed brakes much if the grade was over 6%. I tried regen, but did not have the ability to adjust it. The regen I had was too strong. It was a great brake, but it only let me go down a mountain at 5 mph. That was too slow for me.

On regen trick you should try, connect the regen to a horn button on the bars, so you can get brakes, regen, or brakes and regen at your choice. I liked that in the city.

Does the CA3 give better adjustment for regen drag braking?

Is there anything much better?

I did stop regular use regen long ago, keeping a momentary switch by my throttle to regen only as emergency braking help on slippery surfaces.

Regen was too hard on my 33 lbs motor and fully vented controller, that were frequently overheating. So I had choice of either, riding lower power or limiting the use of regen to a minimum. Since my brakes are perfect, I didn't feel any inconvenience limiting regen to emergency braking only, other than faster wearing brake pads.

I still use regen frequently in the winter, but almost forget they exist during the summer.

Glens carzy ebike said:

can regen kill your hub motor?

Click to expand...

Depends on the strength of the regen, how suddenly / sharply you apply it, how long you apply it, and the temperature conditions at the time, and how much other stuff you do that adds heat to the motor, as well as how well the axle is mounted and secured.

Normally, you wouldnt' have any problems, as long as it's well-mounted and secured, and you're using typical ebike power levels (under 1000w), on more or less level ground.

If you have proportional (variable) regen, and are applying it gradually like you would normal braking, it's unlikely to stress the motor much.

If you have just on/off regen, and its very powerful (say, 40-100A or more, not a common ebike type, then if the motor axle is not up to that you could snap it, regardless of how well it's mounted.

If the axle is not firmly secured to prevent rocking at both ends, fatigue from doing this repeatedly can fracture the axle, usually along the shoulders, or where the wires pass thru the axle.

If you have extremely frequent stops from higher speeds, repeatedly accelerating rapidly and stopping, heat can build up and without thermal rollback in the controller (or cycle analyst) you could eventually damage the motor if it reaches a high enough temperature.

Similarly, long steep hills could do it, braking all the way down...but so could accelerating up the same hill, especially if you are going slow enough.

dogman dan said:

On regen trick you should try, connect the regen to a horn button on the bars, so you can get brakes, regen, or brakes and regen at your choice.

Click to expand...

Or two brake levers, one just inboard of the other, at sligthly different angles, so you use your fingertips to "grab" the ebrake lever or your hand/fingers to grab the regular brake lever. Did that for CrazyBike2 and SB Cruiser, takes a little getting used to, but it works.

Or a button secured to the regular brake lever in a way that you can push it while (or instead of) braking normally.

A more complicated to build but easier to use version would have a "spoon" lever on the forward edge (outside) of the regular brake lever, and that would trigger the regen first, then go into normal braking. If the spoon only covers half the length of the lever, you use your outer fingers to do regular braking and the inner finger to do regen.