Rewinding BBSHD for 72V?

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SwampDonkey   100 W

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Rewinding BBSHD for 72V?

Post by SwampDonkey » Aug 01 2020 1:15pm

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.

district9prawn   100 W

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Re: Rewinding BBSHD for 72V?

Post by district9prawn » Aug 01 2020 1:41pm

Are you trying to lower the kv? The windings should handle 72v as is. Easiest way forward is to simply replicate the existing turn count and wire gauge.
Neu 8057 6kW left hand drive hardtail with 18 fet Vesc: viewtopic.php?f=6&t=96754

SwampDonkey   100 W

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Re: Rewinding BBSHD for 72V?

Post by SwampDonkey » Aug 03 2020 12:11pm

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   10 kW

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Re: Rewinding BBSHD for 72V?

Post by Tommm » Aug 03 2020 12:20pm

You should be doing the opposite, let it rip to 8000rpm++

SwampDonkey   100 W

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Re: Rewinding BBSHD for 72V?

Post by SwampDonkey » Aug 03 2020 1:29pm

Tommm wrote:
Aug 03 2020 12:20pm
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?

Tommm   10 kW

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Re: Rewinding BBSHD for 72V?

Post by Tommm » Aug 03 2020 4:15pm

SwampDonkey wrote:
Aug 03 2020 1:29pm
Tommm wrote:
Aug 03 2020 12:20pm
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/comment ... s_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/bafan ... placement/

thender   100 mW

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Re: Rewinding BBSHD for 72V?

Post by thender » Aug 04 2020 12:05am

I put 72v through mine with 40-50 amps on a regular basis, no modification. No need.

Tommm   10 kW

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Re: Rewinding BBSHD for 72V?

Post by Tommm » Aug 04 2020 4:27am

thender wrote:
Aug 04 2020 12:05am
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.

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Matador   10 kW

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Re: Rewinding BBSHD for 72V?

Post by Matador » Aug 04 2020 8:57pm

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).

Tommm   10 kW

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Re: Rewinding BBSHD for 72V?

Post by Tommm » Aug 04 2020 9:06pm

Higher rpm is desirable so he doesn't destroy the internal gears and driveline.

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fechter   100 GW

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Re: Rewinding BBSHD for 72V?

Post by fechter » Aug 04 2020 9:41pm

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.
"One test is worth a thousand opinions"

district9prawn   100 W

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Re: Rewinding BBSHD for 72V?

Post by district9prawn » Aug 04 2020 10:31pm

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.
Neu 8057 6kW left hand drive hardtail with 18 fet Vesc: viewtopic.php?f=6&t=96754

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