MP4 Regen gives back 27%

[Ron]

I think there are some misconceptions about regen on a ebike.  With my MP4 (MP5 should be the same) I can get 30% regen without killing myself pedaling.  I do always try and use regen to slow down instead of brakes.  I've gotten 33% already this year but didn't take pictures.  Attached picture shows 27% regen.  I found that regen set to max was too strong so I turned it down a bit.  The max amps can be seen in the pictures as 22.1 amps.  My battery is 12s lipo so 44V nominal.  That means the max regen was around 1000 watts. My lipo 12s 15ah pack can, in theory, take a 75 amp charge so I'm within a safe margin unless my pack is freshly charged.  Other battery packs might not like 1000 watts of regen!
The following pictures were taken after the ride from my Cycle Analyst 3. Note the rides start and stop points are the same.

This first picture show the regenerated energy as a percentage.  It also show the amp-hours of battery energy used during this ride.


Amin is the regen amps.  Amax is the max amps the motor used for propulsion, hard to see but it is 31.56 amps. Vmin is the lowest the lipo battery got to during the ride.

[Bikemad]

Amin is the regen amps.  Amax is the max amps the motor used for propulsion, hard to see but it is 31.56 amps. Vmin is the lowest the lipo battery got to during the ride.

Much easier to see with a little bit of enhancement.   



I used to use a pair of wattmeters to measure Ahs used and Ahs returned from regen but I discovered that the meters were not very accurate when compared to each other.

I now use a single wattmeter for measuring battery consumption during use, and simply reverse its direction to measure the Ahs supplied by the charger to ensure better accuracy.
My highest accurately recorded amount of regen was 28.90% on a short test run (without the dog) where I measured 1.723Ah being consumed, but the charger only had to supply 1.225Ah to return the battery to its original 33.4V (0.498Ah was replaced by regen).

Unfortunately, regen current is not being generated at the slow speeds that I ride at nowadays while walking the dog, but I still benefit from the strong electromagnetic dynamic braking effect of the MPII by not having to adjust brake cables (or replace the brake pads) as often as I used to.

Also, the electromagnetic dynamic braking effect is not affected at all by wet rims when riding in long wet grass, unlike the brake pads!   

Alan