Improving MXUS performance

[majornelson]

I have a MXUS geared small "stealthy" rear hub motor from amped bikes. It was my first kit, with a stock controller and a 36v battery bottle. It's been reliable albeit slow with weak torque.

I'm considering putting on a 48v battery and upgrading the controller. Tested it with my 48v em3ev triangle battery and the top speed moved up a bit but acceleration was unchanged (clearly limited by the stock controller- not certain how many amps it puts out.)

Anyone have experience on how many amps this thing can take without toasting it? Not a lot of technical details on the amped site...

Lee

 

[amberwolf]

IIRC using a rear 26" MXUS DD hub on CrazyBIke2, in lots of start-stop conditions, I overheated and damaged halls (at least) in it using a 40A "ecrazyman" 12FET controller. It worked fine up until the day I had to take a detour and ended up doing complete stops and starts every few dozen (or less) feet for a while, in a little backstreet almost-closed-off neighborhood. Details are somewhere in my Crazybike2 thread from about 2.5 years ago, I think. Can't remember for sure.

 

[Drunkskunk]

It depends on the level of modification. 1500 watts in it's pure stock form is no problem. That's ~30 amps at 48 volts. Bumping that up to 40 amps (2000 watts @ 48 volts) should be OK as long as you watch for melting the connectors and phase wires. they are the weakest link. With cooling holes it can handle up to 3000 watts (40 amps @ 72 volts), and probably more if you keep the temps closely monitored.

 

[majornelson]

I may have listed the wrong motor... This is amped bikes small geared motor, not the direct drive one they sell...

I've edited the original post to reflect this.

 

[motomech]

I have a MXUS rear motor from amped bikes. It was my first kit, with a stock controller and a 36v battery bottle. It's been reliable albeit slow with weak torque.

I'm considering putting on a 48v battery and upgrading the controller. Tested it with my 48v em3ev triangle battery and the top speed moved up a bit but acceleration was unchanged (clearly limited by the stock controller- not certain how many amps it puts out.)

Anyone have experience on how many amps this thing can take without toasting it? Not a lot of technical details on the amped site...

Lee

Since you didn't say, I went back and looked though your post to see which MxUS motor you have.
As I recall, the stock controller for the Geared mini-motor would draw 17 or 18 Amps. I had a Hall failure(my fault)and had to replace the stock controller with one that could be used sensorless and went with a Lyen 6 FET Mini-Monster. I had him set it up to 22 Amps max. Using 11S or 12S Lipo(42 to 47 V), there is a big difference over stock. Mine is a frt. mount and I have to take care with the throttle. I think the motor will pull around 800 Watts, max. probably close to the limit for this motor.
With a strong 48V battery, maybe 20 Amps should be about the limit. You could solder the shunt on the stock controller to get that.

 

[Drunkskunk]

Ah. that does change things. 800 watts to maybe 1000 if you are careful. Its a great little motor, but it's a very little motor. so 20 amps is the most I would put into it if I planned to keep it for more than a week.

 

[majornelson]

Thanks guys. I'll pull the controller apart and try soldering the shunt. My memory is to add solder to about 1/3 of it, correct?

I keep it at the beach and it's just a light duty bike I take when we go into town. Just needs a little more zip!

Lee

 

[d8veh]

Soldering about 1/3 the shunt will take it up to about 20 amps. Don't overdo it. Once you go above that, you don't get more torque, the motor just gets hotter more quickly. I found the same as you. 48v gave more speed, but not much more torque.

 

[dogman dan]

Yep, 48v with a small solder of the shunt would be as far as I'd take that motor. Then, easy on how much load you give it. Less weight than a cargo bike, and keep the hills on the shorter side, don't try to run WOT for 20 miles, etc.

 

[Marc S.]

I was abusing a similar sized oil cooled Bafang SWXH geared rear hub in 26" rim with a cheap KU123 controller (12FET, 35A) at up to 15s LiPo.
My well used hub motor (6000km) lasted an other 1400km till the nylon planetary gears melted. Ooops! )

Aside from the Nylon planetary gears, the freewheel clutch is a weak point in these little geared hub motors. I'd strongly suggest oil cooling (and lubricating!) when 'hod rodding' these little motors. Then 20-25A at 14s-15s should be fine.

Now, updated with steel planetary geares, the little oil cooled Bafang is currently serving at 16s (65V) and 25A on my daily commute (the Bafang BPM2 died), till a 9Continent arrives.

 

[d8veh]

My MXUS didn't respond to more current like the Bafangs do.

 

[Marc S.]

My MXUS didn't respond to more current like the Bafangs do.

Thats unfortunate.
Apart from gears and clutch lasting not that long at these power levels (5-6.000km between repairs) both Bafangs can get quite fast (30-40mph) on the flats.