January 14, 20197 yr I have already overvolted my suntour hub and noticed some gains, it's a lot faster however to actually get the extra speed one needs to pedal more or be on a slight downhill. I suspect torque is the main issue, it pulls around 15 amps, the display has option to increase amps up to 20 but this has no effect either up or down so I suspect it's just limited by the shunt. Would upgrading to say a 500w 20 amp controller remedy this? And will the hub be able to take it? I know my battery can handle it
January 14, 20197 yr You are probably running into the speed limit of the hub winding. Next step is to go to 52v. Be very careful with increasing the Amps, you will make more heat but not more speed. I wouldn't go over 16-17 Amps x 48v with a small motor.
January 14, 20197 yr I have already overvolted my suntour hub and noticed some gains, it's a lot faster however to actually get the extra speed one needs to pedal more or be on a slight downhill. I suspect torque is the main issue, it pulls around 15 amps, the display has option to increase amps up to 20 but this has no effect either up or down so I suspect it's just limited by the shunt. Would upgrading to say a 500w 20 amp controller remedy this? And will the hub be able to take it? I know my battery can handle it motors are limited by two constants: Km and Kv. Km is winding independent; e.g., winding a motor with 6 turns with 2 parallel wires instead of 12 turns single wire will double the velocity constant, Kv, but Km remains unchanged. Kv is fixed by the number of turns in the winding and used for selecting the speed of the motor. You have seen the speed increase when you overvolt your motor, that's Kv that does it. Km is fixed by the size of a motor, more turns = more torque and less speed, until you hit the magnetic saturation. higher magnetic saturation = bigger maximum torque = bigger motor. When the motor hits its magnetic saturation, all your extra input Watts will turn to heat. In your case, your motor has hit its magnetic saturation. Increasing the controller's maximum Amp rating is then counter productive.
January 14, 20197 yr Author motors are limited by two constants: Km and Kv. Km is winding independent; e.g., winding a motor with 6 turns with 2 parallel wires instead of 12 turns single wire will double the velocity constant, Kv, but Km remains unchanged. Kv is fixed by the number of turns in the winding and used for selecting the speed of the motor. You have seen the speed increase when you overvolt your motor, that's Kv that does it. Km is fixed by the size of a motor, more turns = more torque and less speed, until you hit the magnetic saturation. higher magnetic saturation = bigger maximum torque = bigger motor. When the motor hits its magnetic saturation, all your extra input Watts will turn to heat. In your case, your motor has hit its magnetic saturation. Increasing the controller's maximum Amp rating is then counter productive. Very informative, thanks. I am pretty satisfied with what I have now anyway, however I may upgrade the hub in time, or maybe even a mid drive. What hub motor would be a good upgrade?
January 14, 20197 yr What hub motor would be a good upgrade? You have for example a 48V 12AH battery. Rule of thumb: maximum battery power is 1.5C, that is 48V * 1.5 * 15A= 864W At maximum yield (83%), the future motor can deliver 864W *0.83 = 717W at the rear wheel. That power should produce 27 mph on a flat road without headwind. Your best choice is a Bafang SWX02C or Bafang BPM CST 500W with winding code 13. https://bmsbattery.com/20-motor You need winding code 13 in all cases. The nearest choice in the UK is the motor on the Oxygen S-CROSS MTB. It may not last very long if you ride on maximum speed all the time. Edited January 14, 20197 yr by Woosh
January 14, 20197 yr Author You have for example a 48V 12AH battery. Rule of thumb: maximum battery power is 1.5C, that is 48V * 1.5 * 15A= 864W At maximum yield (83%), the future motor can deliver 864W *0.83 = 717W at the rear wheel. That power should produce 27 mph on a flat road without headwind. Your best choice is a Bafang SWX02C or Bafang BPM CST 500W with winding code 13. https://bmsbattery.com/20-motor You need winding code 13 in all cases. The nearest choice in the UK is the motor on the Oxygen S-CROSS MTB. It may not last very long if you ride on maximum speed all the time. Sounds good. Like I say I'm pretty happy with what I have, it manages 24/25mph on a flat road hot off the charger. Nominal is closer to 20mph, but can do a lot more with a little push or hill. At least I know what to get if I get bored or melt my hub
January 14, 20197 yr The little Yose hub (cst) still appears to be hardy @48v. My one I believe is 280/290 rpm and with a 20a KT have seen 28mph on the flat, may have got a bit more if I had more then 48/11t top gear. Still super impressed with mine and not burnt it out yet.
January 15, 20197 yr The little Yose hub (cst) still appears to be hardy @48v. My one I believe is 280/290 rpm and with a 20a KT have seen 28mph on the flat, may have got a bit more if I had more then 48/11t top gear. Still super impressed with mine and not burnt it out yet. Depends on your cadence, I'm good for 60 km/h in 48:11 if I could pull that ratio (spoiler: I can't any more...). Watt wise 28 mph (45 km/h) only requires 440 motor Watts at the rear wheel so along with my 160 W for a total of 600 or so Watts it is doable. Are you lying down on the cross bar at that speed? Because of back EMF the GSM could only reliably provide about 42 km/h at 36v so 45 km/h was a bit of an effort on my part. I haven't tried with the 44v battery (yet) but I suspect that it should push the trike along at over 50 km/h on a flat road requiring maybe 500 W because of improved aero. As chance would have it, as I type, a young guy who lives up the road just went whizzing by at about 30 km/h on a 20" wheeled machine on the flat bit of road that goes under the motorway overpass. He is always sitting up straight and very rarely pedalling... Don't know what motor he has but he carries his battery in a backpack.
January 15, 20197 yr Author The little Yose hub (cst) still appears to be hardy @48v. My one I believe is 280/290 rpm and with a 20a KT have seen 28mph on the flat, may have got a bit more if I had more then 48/11t top gear. Still super impressed with mine and not burnt it out yet. Yeah mine will do that with some serious Welly on the cranks. The wind and cold are probably not helping, or maybe my expectations were a little too high. It's still great
January 15, 20197 yr Part of your problem could be that the Suntour motor has been developed as part of a restricted system, whereas the likes of Yose,Bafang etc. are more open and left to the end user to restrict as they see fit.
January 15, 20197 yr Author Part of your problem could be that the Suntour motor has been developed as part of a restricted system, whereas the likes of Yose,Bafang etc. are more open and left to the end user to restrict as they see fit. Not sure on that one. On the suntour system it would cut at 17mph and could easily reach that even when near empty. Due to the difference in voltage I knew it was capable of more. That said I have no doubt there are faster winding codes but the torque may suffer unless amps are increased. I can get it faster than I'm comfortable with anyway, I just need to do a bit of excercise to get there lol
Join the conversation
You are posting as a guest. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.