a 48v 36v Question

[billym1967]

hello all, i have a strange question.

a mid drive 750w 48v, can it be run on a 36v battery. now i understand that it would be bad to run a 36v system with a 48v battery, it it would probably damge the motor. but what would happen the other way round.

 

[Nealh]

The 48v LVC will probably cut in straight away as it will be set to about 42v the max charge of 36v/10s.

 

[billym1967]

yes, i found another tread on it, so that scuppers my idea lol

 

[billym1967]

ive just been reading up on a 48V 750W BBS02 Bafang Central Motor and it lists 36v and 48v batterys, though the 36v is 15ah. stange

 

[Deleted member 4366]

There's a 500w 36v BBS02, or better still, Em3ev sell a 25 amp 36v "250w" BBS02, which is the same, but legal.

 

[billym1967]

the 36v 500w looks intresting, looks to be around £400 i had a look on Em3ev but it looks quite complicated to order off. its knowing what you need.

 

[anotherkiwi]

hello all, i have a strange question.

a mid drive 750w 48v, can it be run on a 36v battery. now i understand that it would be bad to run a 36v system with a 48v battery, it it would probably damge the motor. but what would happen the other way round.

No it is the controller that is at risk or decides which voltage you can use. A motor is just a bunch of magnets and some copper wire wound around a core. My GSM with external controller can be run at any voltage I care to use and now that it is out of guarantee Woosh doesn't care

 

[Danidl]

No it is the controller that is at risk or decides which voltage you can use. A motor is just a bunch of magnets and some copper wire wound around a core. My GSM with external controller can be run at any voltage I care to use and now that it is out of guarantee Woosh doesn't care

... Why do you say that Woosh comes accross as a very caring person....

Any way yes the motor is just as you describe, but overvoltage has consequences..
the insulation , basically only a varnish on the copper coils is very thin and punch through at higher voltages very plausible. The higher voltage will allow more current to flow , heating up those same windings and increasing varnish failure. Higher temperatures, bring the magnets closer to their curie point, where they lose their magnetic fields. .. this point, particular to each magnetic alloy, is affected by both temperature and external opposing magnetic field, in this case the additional current in the windings.

 

[Deleted member 4366]

Any way yes the motor is just as you describe, but overvoltage has consequences..
the insulation , basically only a varnish on the copper coils is very thin and punch through at higher voltages very plausible.

People run those up to 72v. I've never heard of any ebike motor with insulation breakdown. There's been a few that completely burned because too much power was used at too low speed. You should see what people are doing with tiny motors on Endless-sphere. They fill their little 250w Bafang hub-motors with oil and then run them with 20 amps at 72v. Did you know that you can now get a 50 amp 72v controller for a BBSHD? Don't tell Soundwave though.

https://electricbike-blog.com/2016/12/28/kill-yourself-50-faster-with-2x-the-power-e-r-t-s-72v-50amp-3000w-ext-bbshd-controller/

I've personally run 36v motors at 64v using 48v controllers. Nothing blew except the tyres from the wheel-spin.

Basically, you can run any e-bike motor at any voltage. The only consequence is that you have to be mindful of the efficiency. Increasing the voltage increases the motor speed and moves the efficiency curve up the RPM band, so you can't use such high power at low rpm for long.

It doesn't make much sense to increase the voltage much on a crank-drive because it increases the crank speed to faster than what you pedal and reduces the efficiency at normal pedal speed. You'd be much better off increasing the current for more torque.

 

[anotherkiwi]

... Why do you say that Woosh comes accross as a very caring person....

Any way yes the motor is just as you describe, but overvoltage has consequences..
the insulation , basically only a varnish on the copper coils is very thin and punch through at higher voltages very plausible. The higher voltage will allow more current to flow , heating up those same windings and increasing varnish failure. Higher temperatures, bring the magnets closer to their curie point, where they lose their magnetic fields. .. this point, particular to each magnetic alloy, is affected by both temperature and external opposing magnetic field, in this case the additional current in the windings.

Couldn't rate "funny" and "informative" so you got an "agree"...

I completely agree but the OP is talking about 36 to 48 V range and there is not much risk there. Marc S of electrictrike fame, probably one of the people d8veh is thinking about above, melted his nylon clutch gears before anything bad happened to insulation and magnets but he thought he might have been close. Oh and that was at 90V and after 1400 km. Top speed WOT? 68 km/h.

Some motors will survive rougher handling than others, Bafang seems to make quite robust motors other than the nylon gears which many hot rodders have stripped because of high temperatures.

 

[Danidl]

People run those up to 72v. I've never heard of any ebike motor with insulation breakdown. There's been a few that completely burned because too much power was used at too low speed. You should see what people are doing with tiny motors on Endless-sphere. They fill their little 250w Bafang hub-motors with oil and then run them with 20 amps at 72v. Did you know that you can now get a 50 amp 72v controller for a BBSHD? Don't tell Soundwave though.

https://electricbike-blog.com/2016/12/28/kill-yourself-50-faster-with-2x-the-power-e-r-t-s-72v-50amp-3000w-ext-bbshd-controller/

I've personally run 36v motors at 64v using 48v controllers. Nothing blew except the tyres from the wheel-spin.

Basically, you can run any e-bike motor at any voltage. The only consequence is that you have to be mindful of the efficiency. Increasing the voltage increases the motor speed and moves the efficiency curve up the RPM band, so you can't use such high power at low rpm for long.

It doesn't make much sense to increase the voltage much on a crank-drive because it increases the crank speed to faster than what you pedal and reduces the efficiency at normal pedal speed. You'd be much better off increasing the current for more torque.

... As someone who lost the compressor in an expensive air to water heatpump requiring a new installation due to insulator failure in the windings it's a sore point with me. I agree that in a low voltage supply such as 40 volts , manufacturing practice in painting on the varnish, probably give a thicker coating then optimum and a higher breakdown voltage . Unfortunately I had not that luxury at 220v
When the motor burns out due to overheating, it will be because the varnish has melted or oxidised, or allowed punch through as it's resistance drops at high temperatures. A hotspot forms and ..... We all know the smell. This will occur well below the melting point of the copper.