Help! Upgrading a Bafang rear hub motor - struggling to find a source

[spleenharvester]

Hi all,

I currently have a basic G010.250.D motor in my Falcon e-bike (20" wheels, 36 spoke, 36V system, upgraded to KT36/48 15-amp controller). I'd like to upgrade to something with a bit more torque. It seems to me like the G070.350.D would be the best possible upgrade at double the torque of the G010. Only problem is I can't source the damn thing, anywhere, or even the similar looking G040.250.D. I've found one source for the G070, but it's from somewhere in Poland that doesn't have any reviews at all so I'm not sure it's legit. I can find G020 series, but the torque upgrade is only small (32Nm vs 45Nm).

Have Bafang discontinued the G series or something? Or are they only selling to wholesalers? If I can't find one are there any other manufacturers that would fit/work with a KT controller?

Cheers

 

[saneagle]

The torque comes from the controller, not the motor, If you want more torque, you need more amps. On some KT controllers you can turn them up in the settings. Torque is more or less directly proportional to amps, so a 3 amp increase would give 20% more torque. Your battery can probably go up to about 20A, but without having the tech specs, that might put it on the limit and prevent the use of a 20A or 22A controller. Running with higher current can actually make your motor run cooler because faster means more efficient, but the controller will run hotter if you use too much power for tool long. It should be fine with a 3A increase.

If there's no way to increase current in the settings, you can do it by adding some solder to the shunt in the controller. basically you get an increase in current in proportion to the length that you solder, so 10% soldered gives 10% more current. Do it a bit at a time to see whether it meets your needs, but don't go over 25%.

Another solution is to go up to a 48v battery, which would give an instant 30% increase in torque and more top speed if you want it.

All things considered, I'd go for a 48v battery. It gives a lot more options for torque, power and speed. Check the settings in your controller first because that's very quick and might give you what you want for nothing. Some go as high as 20A, so you can test whether your battery will cut out.

If you just changed the motor, there would be approximately zero difference. When they mention the torque in the listings, its more about how much they can handle rather than how much they give. Some motors have a higher internal reduction ratio, which can give an advantage, but they still make more or less the same torque at the same current and wheel-speed as any other motor.

 

[spleenharvester]

You've saved me a ton of money then, thanks very much! Seems KT controllers only support changes to current via the P3 parameter, imitation torque vs speed. Imitation torque is a tiny bit snappier.

I did look at a 48V system but was struggling to find a decently branded battery within my price range.

I might give a 22A controller a go, they're fairly cheap and I can always sell it on if I do get cut outs.

Thanks!

 

[saneagle]

You've saved me a ton of money then, thanks very much! Seems KT controllers only support changes to current via the P3 parameter, imitation torque vs speed. Imitation torque is a tiny bit snappier.

I did look at a 48V system but was struggling to find a decently branded battery within my price range.

I might give a 22A controller a go, they're fairly cheap and I can always sell it on if I do get cut outs.

Thanks!

Not P3 which is general riding mode, Set that to torque simulation. You want C5 - max current.

I just fitted one of these batteries. the compay seems pretty good - very responsive and helpful when i made a mistake on the order. The battery is on my bike and working - just need some good weather to fully test it. I ordered it in the evening and it would have been delivered next day if UPS didn't let us down. Eventually, it took 40 hrs from order to delivery, and I didn't pay for the fast delivery, which would have been more expensive. Try EASTER10 discount code. It worked for me to get 10% off the already very reasonable price. Their 48V 13AH battery is only going to be £170 - suck on that Bosch and Yamaha guys.

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[spleenharvester]

Ah good catch, C5 is already set to 10 - max current unfortunately :-(

I'm a bit wary of those Heilong-style batteries because you never know what they're filled with, especially when they don't show pictures of the internals!

Btw do you happen to know if it's worth upgrading the KT-LCD4 to a KT-LCD8? Can't find much info on the differences between them, besides the KT-LCD8 having a fancier screen

 

[saneagle]

Ah good catch, C5 is already set to 10 - max current unfortunately :-(

I'm a bit wary of those Heilong-style batteries because you never know what they're filled with, especially when they don't show pictures of the internals!

Btw do you happen to know if it's worth upgrading the KT-LCD4 to a KT-LCD8? Can't find much info on the differences between them, besides the KT-LCD8 having a fancier screen

They all work the same, except sometimes the cheaper ones(LCD1 and LCD5) don't give you access to all the parameters. What can happen is that the resellers get surplus stock when there were some left over from a factory ebike assembly run, and sometimes the customers wanted special features in the LCD, like passwords and blocked settings, so you never really know what you're going to get, though mostly they're standard, especially from the resellers we know, like Topbikekit, PSWPower, BMSBattery, etc.

I don't think battery quality is anything to worry about unless you want to run a very high power system. Some have better cells than others, some last longer than others and some cost twice as much as others. If you pais £170 for one, you can offord to buy two compared with a £340 one, and if they only last 80% as long as the £340 one, you're 60% up.