Following my hub failure the wife's also went, just the nylon gears, but as it was rusty and spokes kept breaking we opted for a new wheel. She has ordered a 500w direct drive for the cheapness and reliability. Her current controller is a kunray 6 fet 15amps, will this be enough for such a big hub? Mine feels like 25amps just wakes it up. Will a 6 fet survive a shunt mod if it's weak? I've done it before at 36v but I think 48v might cook it
Direct drive hub, 15 amps controller enough?
- Thread starter anon4
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Hell no! Direct drive (DD) motors are absolutely gutless running on 15A. I'm of the opinion that DD motors are pointless running below 35A, since geared motors are able to reliably generate similar torque levels up to around this point.
Hey I just realized I posted in the wrong section, oh well. Yeah was suspecting that, it comes as a kit with a bigger controller but it's 36v so will probably not work. Will see how it is, have a couple spare 6 fets if the shunt mod kills it but will probs just upgrade fairly soon. My hub is fine at 25a tbh 35a would probably be fantastic but doubt my cheap battery (or hers) is capable
The 15 amp controller will overheat because its only rated for 7 amps. 15 amps is the max it will give, which would normally only happens occasionally, but with only 15 amps, the motor most likely won't be able to get up to its efficient speed, so it will be drawing the maximum current all the time. A lot depends on what speed the motor is wound for.
I'd say that you need at least a 22 amp controller for one of those motors at 36V.
A shunt mod will only make it overheat more. I wouldn't recommend it.
I'd say that you need at least a 22 amp controller for one of those motors at 36V.
A shunt mod will only make it overheat more. I wouldn't recommend it.
It's advertised at 22mph but we'll be running it at 48v so it'll be more. Pretty sure we're going to have to invest in a new controller then unless the included one is dual voltage. They are cheap enough so not a big deal, a bigger problem is it won't fit in the box but she has space under her rack for a nice stealth setup
Mines running a 9 fet 25a and it runs just fine, no excess heat or anything like that
Hill torque is acceptable if not great, I've ridden 250w setups that have been worse. Will probably be ok on longer rides as we have mostly flat commutes, there are a few gruelling climbs we do but they are pretty short, just depends how much heat builds up in the controller during those. Tbh the hills in question are such a slog to get up that it's probably running max amps anyway, has overheated twice previously with a motor short error until the fets cool down. This could happen more frequently with the more hungry motor if it gets warmer prior to the climbs, I don't think it'll just blow up I think it'll just have thermal cutouts more often. But who knows? Might get the magic smoke tomorrow then I'll be tasked with pedalling a great lump home because she can't do it with her bad hips
The problem is the speed of the motor. At legal speeds, there is insufficient back emf, so the controller will allow maximum current all the time. If it's a KT controller set to current control (torque simulation), it'll be OK as long as you don't leave it on level 5. If it's any other type of controller without current control, it's going to get hot.
It seemed ok today, it struggled with a steep hill though, definitely needs more amps. Didn't get any cutoffs yet though. It just needs to survive until a suitable replacement arrives