Noq wrote:Awesome looking project! Love the welder and the workshop setup you got going on. Definitely have the skillset to make a successful conversion. It's cool what you did with that half of the stock chainstay/swingarm. That's gonna be a fabulous whip. I think I briefly had the same QS 4kW 10" V3 motor as you. Nice choice.
Now I use different batteries than you (Leafs), but one thing I'd recommend at first glance is if you're using the 80A BMS, if you can, set it up so that you charge through it to balance, but don't output through it. 80A is way too limiting an output bottleneck for your system. 60V * 80A = 4800W, and you've got a 4kW motor, but of course you know you can do way more than 4kW through it at burst. Heck, even my 500W stock motor pulls two or three times more current than that at peak on a 20S system (highest was a 290A spike at around 75V). It's for the briefest moments at dead-start you'll spike like that, so if you're careful, no damage. Steady drive is much lower current, so it can handle it. You can also mount your own thermistor to monitor heat, which beats touching the casing to check. So why sacrifice your startup torque/burst limits? I wouldn't be surprised to see you get away with 15kW bursts through it, easy. I had a 100A BMS to charge through, but wouldn't have dreamt of outputting through it with my 500A controller on my 8kW QS motor from 2013. That thing made it up way, way higher than anyone expected for quite a long time, and it was an old model (40-50kW bursts, continuous drive >1h at 10-15kW). These QS motors, they can handle it. Just remember, if you open the motor to sink a thermistor, seat the 'mistor under the copper, but high-heat epoxy it to the stator material and try not to get any glue on the copper or you'll create a heatbed. When you close up the motor, seal it with metal-bonding silicone to combat water ingress. Sorry if you already know these details; just sharing some things I learned with QS tech in the past couple years daily driving it. May as well know about it. Of course, be careful over-driving it, and maybe don't peel-out every chance you get, lest you fancy burning your stator coils.
Wow Noq, those are all great tips! This is exactly what I was hoping for when I made the thread.
The BMS uses the same ports/connections for charge and discharge, so does that mean I should connect to the BMS when charging, and connect past it when driving? Should be doable, but something tells me it is also good to have the BMS there while driving, or no? It is protected for over charging at 80A, which of course limits the whole system to just above nominal power (like you said). BTW, do you know if the Kelly controller (the programmable one) can be programmed to limit acceleration, so as to limit the worst peaks from dead-start?
I must say I'm looking so much forward to receiving the motor and controller (+ throttle and disc brake), so I can start on the design and fabrication of the mechanial bits. Being a mechanical engineer I'm looking forward to a little break from all the electrical stuff
It's expected to arrive tomorrow!
About the thermistor, I'm not sure I dare opening up that brand new motor, I've had mixed luck when opening up alternators and starter motors to refurb them
Robert at QS told me it was too late to add the thermistor, so is it really that simple?