Upgraded Fat Tire bike stopped running, something seems Burnt!!

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banshee28   10 mW

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Upgraded Fat Tire bike stopped running, something seems Burnt!!

Post by banshee28 » Jun 10 2021 9:24pm

Hey guys, need some help here!!

So, I upgraded my fat tire bike with all new components: 52V 21Ah battery, 35A controller, Color LCD, 750W Bafang rear Hub, throttle, etc. Everything was working good for a month or more across all terrains, no issues!

Last ride, I rode in some heavy beach sand areas and had some low speed areas where I used full throttle at very low speed. I think this may have really been a bad idea, but it seemed to handle this fine on previous rides.

I did look down at the LCD at times and notice 1200-1500 or so watts showing so i know at brief times it was working hard.

Anyway, during this ride the motor and LCD eventually turned off and would not turn back on. I peddled home and let it cool down. Still no power. Nothing seemed hot or burnt at the time. I disconnected the battery to the controller and let sit overnight.

The next day, I try to plug things back in and quickly heard a sizzle and seen the battery terminals turn black while plugged in to the controller!! I also notice while pushing the bike backwards there seems to be a slight more resistance in the motor.

So I would like some help here on the possible issue. Did I overload or burn out the motor, controller, battery, hopefully not ALL of them, LOL

Any suggestions on how to check things out?

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pwd   10 kW

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Re: Upgraded Fat Tire bike stopped running, something seems Burnt!!

Post by pwd » Jun 11 2021 7:39am

It's likely that you burnt up the controller and/or have damaged the phase cables from the motor to the controller. Is it a geared or direct drive hub motor? I'd start by inspecting all your connectors and cables for damage and then move on to controller troubleshooting:

https://ebikes.ca/documents/BlownMosfets.pdf
https://www.youtube.com/watch?v=lTssCn5YyTw
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Rocky Mountain Element
Magic Pie 4 front w/ Infineon 4 Clone @ 70A phase + Leafmotor 1500 rear w/ Infineon 4 Clone @ 200A phase
Samsung 40T 14S7P

Offroad Build viewtopic.php?f=6&t=102195:
2019 Rocky Mountain Blizzard 20
Cyclone "3kw" 13T motor to 36T chain ring then 32T chain ring to 11T-46T Cassette @ 100A phase
Molicel P42A 21S3P

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banshee28   10 mW

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Re: Upgraded Fat Tire bike stopped running, something seems Burnt!!

Post by banshee28 » Jun 11 2021 8:17am

Thanks, its a geared hub. It was originally the 350W version, but I swapped in the "guts" of a new 750 into the case, which is a perfect fit. I will check the cables but I don't think any are burnt or damaged enough to see on the outside, but will disconnect and check today.

Not sure how to troubleshoot the other stuff? Can I use a volt meter and check battery and things to make sure its still ok?

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fechter   100 GW

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Re: Upgraded Fat Tire bike stopped running, something seems Burnt!!

Post by fechter » Jun 11 2021 12:08pm

Unplug the motor from the controller and see if the abnormal resistance to pushing backward disappears. If so, the controller is shorted. You can also check the controller with an ohmmeter once the motor is unplugged. Measure resistance from each phase wire to B-. Reverse the meter probes and measure again. Repeat measuring to the controller B+ wire. If any of these measurements show near zero ohms in both directions, the controller FETs are shorted.
"One test is worth a thousand opinions"

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banshee28   10 mW

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Re: Upgraded Fat Tire bike stopped running, something seems Burnt!!

Post by banshee28 » Jun 11 2021 2:06pm

fechter wrote:
Jun 11 2021 12:08pm
Unplug the motor from the controller and see if the abnormal resistance to pushing backward disappears. If so, the controller is shorted. You can also check the controller with an ohmmeter once the motor is unplugged. Measure resistance from each phase wire to B-. Reverse the meter probes and measure again. Repeat measuring to the controller B+ wire. If any of these measurements show near zero ohms in both directions, the controller FETs are shorted.
Thanks will do this next!

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banshee28   10 mW

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Re: Upgraded Fat Tire bike stopped running, something seems Burnt!!

Post by banshee28 » Jun 12 2021 11:24pm

fechter wrote:
Jun 11 2021 12:08pm
Unplug the motor from the controller and see if the abnormal resistance to pushing backward disappears. If so, the controller is shorted. You can also check the controller with an ohmmeter once the motor is unplugged. Measure resistance from each phase wire to B-. Reverse the meter probes and measure again. Repeat measuring to the controller B+ wire. If any of these measurements show near zero ohms in both directions, the controller FETs are shorted.
Update: I think good news, I unplugged and it DID seem like the motor spins easier now! So does this mean its shorted and needs to be replaced or do I need to test further? It would be nice if it was only the controller and both motor and battery are OK.
Thanks!

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fechter   100 GW

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Re: Upgraded Fat Tire bike stopped running, something seems Burnt!!

Post by fechter » Jun 13 2021 11:18am

If the motor spins easily with the controller unplugged, then the motor is probably OK. You need a new controller.
"One test is worth a thousand opinions"

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banshee28   10 mW

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Re: Upgraded Fat Tire bike stopped running, something seems Burnt!!

Post by banshee28 » Jun 14 2021 10:23pm

fechter wrote:
Jun 13 2021 11:18am
If the motor spins easily with the controller unplugged, then the motor is probably OK. You need a new controller.
Great, hope so!! I will run a quick test on the battery ASAP, hope it is ok too. If so will order a new controller soon. Any suggestions on which model, maybe there is a better one than what I had here (35amp 36-52v KT Controller).

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