Bafang G510 Ultra Max Mid Motor Overheating

RMK!

Well-Known Member
I have the large 90lb ebike (pictured below) with the Bafang G510 Ultra Max Mid Motor 1000W motor. I've put just under 2000 miles on it since Jan 2021. Now that the warmer weather has arrived I have noticed that when riding it hard and fast the motor case gets hot to the touch and the motor loses power. It may be there is a temp control sensor that limits the motor power if overheating but I'm not sure. Although the weather has been warm (mid 80's) it can get quite warm where I live mid summer and I'm concerned about motor longevity due to temp issues.

The bike came direct from China so the tech support is a little sketchy. I'm just wondering if anyone had heard of or experienced this with the Ultra motor.
Minus Front Fender.jpg
 

theemartymac

Well-Known Member
There will be a temp sensor with a safety limit in there. You can also be hitting the battery limit too when drawing too much power for too long as well. Feel your battery and see if it gets more than lukewarm too. The batteries have no cooling, and the case insulates well, so a warm case can be a sign of outright hot cells.

The obvious stuff is not to lug the motor, and not to pull too much power at low drivetrain speeds. Any energy that the motor receives that it can't covert to rpms is converted to excess heat. So pinning the throttle/using high PAS settings at low speed and/or in high gear is just turning your motor into a portable heater.

I ride a similar bike hard and fast, and I'm 300lbs, and I can't even get the Ultra motor noticeably warm (but the case is an insulator, so that isn't saying it's not hot inside). But speed runs do draw a lot of continuous power, so I can get my batteries (and likely the controller) quite warm, and have a couple of times noticed the power fall off by being lazy with my energy management for too long. The Ultra is a beast, so I would suspect you would fry your controller before the motor.

I've also seen postings by some techs on this site that the stock lithium grease can disappear over time, so it might be worth a repack - if you can get a spare gasket.
 

RMK!

Well-Known Member
There will be a temp sensor with a safety limit in there. You can also be hitting the battery limit too when drawing too much power for too long as well. Feel your battery and see if it gets more than lukewarm too. The batteries have no cooling, and the case insulates well, so a warm case can be a sign of outright hot cells.

The obvious stuff is not to lug the motor, and not to pull too much power at low drivetrain speeds. Any energy that the motor receives that it can't covert to rpms is converted to excess heat. So pinning the throttle/using high PAS settings at low speed and/or in high gear is just turning your motor into a portable heater.

I ride a similar bike hard and fast, and I'm 300lbs, and I can't even get the Ultra motor noticeably warm (but the case is an insulator, so that isn't saying it's not hot inside). But speed runs do draw a lot of continuous power, so I can get my batteries (and likely the controller) quite warm, and have a couple of times noticed the power fall off by being lazy with my energy management for too long. The Ultra is a beast, so I would suspect you would fry your controller before the motor.

I've also seen postings by some techs on this site that the stock lithium grease can disappear over time, so it might be worth a repack - if you can get a spare gasket.
Good points all ... I have been going fast, in high gear with throttle and pedal but not shifting enough and not keeping the cadence high. It's just too much fun going 35+ mph on these big bikes road/trail allowing. I will back off a bit and try your ride tips.
 
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RMK!

Well-Known Member
My riding style must have caused the over heating. I rode +/- 35 miles several times this week in warm weather and no issues. I got out of the shifting habit when I had a Sturmey Archer 5 speed IGH belt drive on the bike. This drivetrain was so fragile that I kept it mostly in high gear relying on PAS and throttle to get me up hills. Recently, I replaced the SA IGH with a SRAM 9 speed cassette chain drivetrain and now, I can shift as needed without the drivetrain constantly slipping and phantom shifting gears. Not shifting under load is key to keeping your drive train in tact.

The irony of this was I chose the SA IGH based upon supposed reliability vs a standard chain/cassette setup. The reality is that an inexpensive (cheap) IGH isn't compatible with a powerful mid-drive motor like the ultra.