Rewinding BBSHD for 72V?

SwampDonkey

100 W
Joined
Mar 27, 2018
Messages
227
I plan to try this out. Ive never rewound a motor before, but I happen to have a toasted BBSHD stator on hand.The rotor is fine,so are the magnets and laminations.

Does anyone know what wire gauge and number of turns would be ideal for something like this? Id like it to handle 72V.
 
Yeah Im definitely wanting to bring down the KV by about 15%. Does anyone know for sure what the original number of turns is? hard to tell, but it looks like 3 on this motor.

Lets say I did want to bring down the KV. More turns? Fewer? Thicker wire? Thinner? I think I would like to go with thicker wire if possible.
 
Tommm said:
You should be doing the opposite, let it rip to 8000rpm++

Sure, so how would one go about doing that? Does anyone know what the stock number of turns is on the BBSHD motor?
 
SwampDonkey said:
Tommm said:
You should be doing the opposite, let it rip to 8000rpm++

Sure, so how would one go about doing that? Does anyone know what the stock number of turns is on the BBSHD motor?

Kv is very low, similar to cyclone. About 22x reduction to chainring. Claimed rpm 160rpm there, so around 3500 on 48v. About 70 kv.
https://www.reddit.com/r/ebikes/comments/5cubs6/does_anyone_know_the_kv_rating_and_number_of_pole/?utm_source=xpromo&utm_medium=amp&utm_name=amp_comment_iterations&utm_term=active_search&utm_content=comments_view_all

Bbshd has magnets inside the metal core. That means less of a chance of the magnets flying off at speed. You could easily double kv if using 52v, or 1.5x if going for 72v.
https://california-ebike.com/shop/bafang-bbshd-1000-motor-rotor-replacement/
 
I put 72v through mine with 40-50 amps on a regular basis, no modification. No need.
 
thender said:
I put 72v through mine with 40-50 amps on a regular basis, no modification. No need.
He roasted his windings already. So has to repair it somehow.
 
With a 52V 14S Li-ion battery hot off the charger 58.8V), my 30A BBSHD spins at 180 rpm at the bottom bracket crank (or 155 rpm at the nominal 50.4V).

If you somewhat overvolt it (you'll need a different controller than the stock which only has max 63V capacitors) to 72V, it should spin around 220 rpm at nominal 72V (or a bit less is you account for inefficiencies). So you will gain top speed, but torque will remain the same.

On the other hand if you rewire the motor to keep the same 155 rpm but while voltage is at nominal 72V (20S) instead of nominal 50.4 V (14S). Then top speed will remain the same, but you will have much more torque (and with the same 30 amps amps).
 
Higher rpm is desirable so he doesn't destroy the internal gears and driveline.
 
The best way to figure out the number of turns is to count what you get when you take the old ones off. You also need a VERY detailed diagram of how the windings were placed so you can put the new ones on in the exact same configuration. Once you get one of the windings off, you can count how many strands were used and try to measure their individual diameters. Then there are charts or formulas you can use to calculate how many strands of what gauge wire to fill the slots for a desired number of turns.

Running it at higher speed is likely to melt the plastic gear. Look for a metal one. If you gear the bike so the motor loading stays close to stock, which means not going faster than about 30mph, then the plastic gear might hold up. Above 30mph, it just takes too much power to sustain that speed regardless of motor rpm and the gears won't like it.

The stock number of turns is probably going to be good for 72v. If you put one more turn, you can get more torque for a given current, which might make the controller and battery happier.
 
district9prawn said:
I have seen various chinese motors with 12 stator teeth and 8 magnets (just like bbshd). The winding scheme is usually ABCABC. Coils on the same phase wound in series.
Do you mean like this?
 

Attachments

  • BBSHD winding diagram.png
    BBSHD winding diagram.png
    29.3 KB · Views: 692
Back
Top