Bafang m820

[clix]

I don't agree with this, actually I try to spin higher cadence with this because the motor seems to be working better that way.

Well, ok. High cadence is a bit arbitrary. What is high for some, is not high for others. Spinning at 90rpm is most of the time fine, especially with higher battery percentage. But higher, 120 for example, there is a very noticeable drop in power. For some this is not an issue at all.
When things get steep, I like high cadence. Not for long periods of time, but for few seconds, to get over the steep bit. In this situations I notice, that things can be improved. Especially, because at lower cadence there is SO MUCH torque. I would prefer If this curve would be shifted a bit to higher cadences.

 

[ficorama]

Well, ok. High cadence is a bit arbitrary. What is high for some, is not high for others. Spinning at 90rpm is most of the time fine, especially with higher battery percentage. But higher, 120 for example, there is a very noticeable drop in power. For some this is not an issue at all.
When things get steep, I like high cadence. Not for long periods of time, but for few seconds, to get over the steep bit. In this situations I notice, that things can be improved. Especially, because at lower cadence there is SO MUCH torque. I would prefer If this curve would be shifted a bit to higher cadences.

power drop above 120rpm is normal, it happens with all engines. however, the m820 is not a full power engine!

 

[clix]

power drop above 120rpm is normal, it happens with all engines. however, the m820 is not a full power engine!

You don't have to explain anything to me. M820 is not a bad motor. It has more than enough power and also a lot of torque at low cadence. But, my experience is, that at higher cadencees, torque tapers off a bit faster than with the competition. That's it...

 

[ficorama]

You don't have to explain anything to me. M820 is not a bad motor. It has more than enough power and also a lot of torque at low cadence. But, my experience is, that at higher cadencees, torque tapers off a bit faster than with the competition. That's it...

what competition?

 

[clix]

what competition?

Other lightweight motors. Fazua, tq, Bosch sx,..

 

[ficorama]

Other lightweight motors. Fazua, tq, Bosch sx,..

did you drive them all?

 

[ficorama]

Other lightweight motors. Fazua, tq, Bosch sx,..

what firmware are you using?

 

[clix]

what firmware are you using?

FW attached, but I don't think there is anything wrong with my unit.
Anyway, here is last years review of different ligthweigth motors. One of them is forestal, that has EON drive, (bafang M820 brother).
https://www.bike-magazin.de/komponenten/e-bike-motoren/leichte-e-bike-motoren-im-test-fazua-tq-forestal-specialized-ep8rs/
Near the bottom of the review, there is power curve:

Few things to note (and some to speculate):
-Forestal uses 52V (14s), battery and BAFANG ligthweigth battery is 43V(12s, this one I also have).
-basicaly, due to the "back E.M.F". and particular motor design(armature design, number of stator poles,..), each motor has max RPM. Also higher the voltage (with the same motor design) higher the max RPM
-most of the people on here are saying, that 36V/43V/48V M820 motors are identical, apart from FW. Then, it would be reasonable to believe, that EON in forestal has the same motor internals. That would indicate, that with 43V battery, M820 higher cadence performance is even sligthly worse than the one in the picture.
-I would also asume this is the reason forestal went with 52V battery, to help with the assistance at higher voltages
-upper graph also corelates quite a bit to my experience with M820. And as the battery drains, voltage is lower, and the performance at higher cadances becomes worse. I also notice this.

so, overall, not a bad motor, but also not the best.

 

[mike_kelly]

I doubt seriously that the Bafang motors are all the same and it is just firmware. The relationship between rpm and kv is linear. So if you had a constant kv, due to the same motor, a 36v motor would run 36/48=.75 or 25% slower.
You can't change that in firmware.

 

[ficorama]

FW attached, but I don't think there is anything wrong with my unit.
Anyway, here is last years review of different ligthweigth motors. One of them is forestal, that has EON drive, (bafang M820 brother).
https://www.bike-magazin.de/komponenten/e-bike-motoren/leichte-e-bike-motoren-im-test-fazua-tq-forestal-specialized-ep8rs/
Near the bottom of the review, there is power curve:
View attachment 139814
Few things to note (and some to speculate):
-Forestal uses 52V (14s), battery and BAFANG ligthweigth battery is 43V(12s, this one I also have).
-basicaly, due to the "back E.M.F". and particular motor design(armature design, number of stator poles,..), each motor has max RPM. Also higher the voltage (with the same motor design) higher the max RPM
-most of the people on here are saying, that 36V/43V/48V M820 motors are identical, apart from FW. Then, it would be reasonable to believe, that EON in forestal has the same motor internals. That would indicate, that with 43V battery, M820 higher cadence performance is even sligthly worse than the one in the picture.
-I would also asume this is the reason forestal went with 52V battery, to help with the assistance at higher voltages
-upper graph also corelates quite a bit to my experience with M820. And as the battery drains, voltage is lower, and the performance at higher cadances becomes worse. I also notice this.

so, overall, not a bad motor, but also not the best.

View attachment 139812

everything is on paper. but forestal motor is 60nm and m820 is 75nm. I don't think any comparison makes sense here! According to their specifications, the forestal motor weighs 1.95 kg and the m820 weighs 2.3 kg. so there are differences.

 

[ficorama]

I doubt seriously that the Bafang motors are all the same and it is just firmware. The relationship between rpm and kv is linear. So if you had a constant kv, due to the same motor, a 36v motor would run 36/48=.75 or 25% slower.
You can't change that in firmware.

the engine from forestal and the m820 look the same from the outside, as I wrote in the post before, the information and the weight alone indicate that the engines are not the same.

@clix I don't know if your FW is road. I tried e-mtb and e-road firmware. in terms of strength equally. and as far as driving characteristics are concerned, the road fw is much lazier in its reactions! there is no overrun either. so maybe that bothers you. maybe you should try 36v emtb fw to see if there is a difference.

 

[clix]

@mike_kelly , @ficorama , if someone would actually open different voltage motors, and check the windings and gearing, that would be great. I would be very interested.

I attributed different weight between the EON and M820 to different material being used in the gears, axle(more aluminum and or titanium?), but presumed that mechanically and electronically they are identical.

 

[ficorama]

Hi guys. yesterday while driving I saw 620W in boost on the screen.
battery full 11s 46.2V.

that's serious power for such a small engine.

 

[Adam Anderson]

M820 on an electric gravel now in BAFANG's booth in China Cycle

Electric gravel bike compatible with bafang m820 #electricbike #ebike #egravel #ebikes

 

[voigtkampff]

M820 on an electric gravel now in BAFANG's booth in China Cycle

Electric gravel bike compatible with bafang m820 #electricbike #ebike #egravel #ebikes

is it equipped with bottle cage range extender? could it be that bafang made it officially supported option?

 

[Adam Anderson]

is it equipped with bottle cage range extender? could it be that bafang made it officially supported option?

there is only one battery as the bottle is.

 

[voigtkampff]

there is only one battery as the bottle is.

Please elaborate. Is this awkward-looking, blockish bottle actually a watter bottle not a battery or there's no downtube battery and the only battery is this blockish bottle?

 

[Adam Anderson]

Please elaborate. Is this awkward-looking, blockish bottle actually a watter bottle not a battery or there's no downtube battery and the only battery is this blockish bottle?

this is the battery, and the only power source on the bike. TBH, I think the design is nice. BTW, there are conversion kits company offering this bottle battery, too.