great idea I suspect you are right most people go power mad and fit the most power they can bbshd 1700watt and 52 volt battery but I think it may work if we all collaborate the answer may be found

Nice one, makes more sense now. I knew that a motor could be used as a dynamo, but hadn't considered it would be producing voltage when used as a motor. As you say this is down to the physical characteristics of any given motor and can only really be changed by external gearing, hence why I asked earlier how this could be improved by firmware or controller improvements.

There is one thing you can do with the controller. You still see it on some controllers, and that's then three speed switch. You get an extra connector with three wires. One is ground and the other two are basic digital inputs to the controller, so the switch only acts as a command to the controller when to operate high-speed mode. High-speed mode changes the timing slightly - a bit like you can with an internal combustion engine to get more torque or speed. I'm not sure about exactly how the changed timing deals with the back emf, but the end result is a 10% boost in maximum speed.

 

Not all three-speed switches do the timing change. some are just programmed for different speed limits. The KU63 controller that we used to buy from BMSBattery used to have it.

Changing the gearing won't help your natural cadence which sounds to be similar to mine at about 100-110?

 

If you put a bigger chainwheel on to slow your cadence you will be running into other issues. The GSM is a BBS01 clone and is supplied with a 46 tooth chainwheel, it is on a 28" wheel bike at the mo'. I managed to stall the motor with that and an 11-32 cassette so went to a 42-32 double chainring on the front. The 42 is a little too small, a 44 is probably the ideal for a 28" wheel but with the 32 I can climb anything in bottom gear, seated...

 

The motor will be moved to the trike which is 26" rear wheel so the big chainwheel will be upgraded to a 48 tooth. At the moment the cassette is an 11-40 8 speed but I think I will upgrade to 11-46 10 speed. I have also ran the ratios for the stock single 46 tooth chainwheel (http://www.bikecalc.com/speed_at_cadence) which is also an option as 1x10. I hardly ever use the 11 tooth top gear feeling more comfortable in 48:13 which still gives about 55 km/h before spinning out. 46:13 is still a healthy 50 km/h and the 11 tooth is always there for those moments you must be pedalling at 60-65 km/h...

 

The advantage of the GSM external controller over the BBS0x is... the external controller! I have tried 12S - 44.4v nominative battery and hot off the charger seen about 680 Watts on the LCD. That is too much for the 36v controller I have at the moment which is using the thermal cut off to save it's skin. Although all that power is lovely I expect to run a 48v controller at 12 Amps which gives the same power as a 36v at 15 A give or take a Watt or two. The cadence of the motor is 110 rpm with a 44.4v battery so no back EMF in the tests I have done so far.

Maybe then it may be worth trying the BBS01 with an external controller at 48v and 12A to improve the back EMF effect. Not sure if the Bafang PAS will work, but I think it would be possible to fit an external one on the non drive side.

Is that what a gsm sold by Woosh £199 for the 36v can it be over volted ?

Yes, same unit