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

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banshee28   100 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
2WD Commuter/Street Build viewtopic.php?f=6&t=98286:
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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
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banshee28   100 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   100 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   100 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   100 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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banshee28   100 mW

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

Post by banshee28 » Sep 06 2021 10:19pm

Crazy how life gets in the way of important things, LOL.

So I was finally able to get this working again! Simply replacing the controller with a new one did the trick. It connected up, no sparks and runs like a champ. Battery was still showing 56v after all this time so very happy.

Now, lessons learned:

Would I buy another HUB bike: Absolutely...... However there is a place and environment for them, lol. I will never torture this HUB in this way again! I may still take it in heavy terrain, however with as much pedal assist as I can from a start, and always starting off easy from a stand still. Without gears, they need to stay in their proper RPM most of the time.

Also, I am now looking for my dream mid drive setup, so I can properly ride in ANY terrain with this type of setup!

Was thinking OEM, but of course, very costly and still not a perfect setup of components.

As of the last few days, kinda leaning towards buying a very nice used DH bike with good components, and putting on the new CYC X1 Pro Gen2 and DIY.... :D

Still researching that and may post one day...

Anyway, thanks for the help getting this one back to normal!! :bigthumb:

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fechter   100 GW

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

Post by fechter » Sep 07 2021 10:12am

Glad to hear you got it working. Ideally, the motor and controller should both have temperature sensing that will start limiting the power if things get too hot. Adding a couple of thermistors can't be that expensive, but very few DIY setups have it.
"One test is worth a thousand opinions"

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MoneyPit   100 mW

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

Post by MoneyPit » Sep 07 2021 10:34am

Out of curiosity, was this a Sondors fat bike? One of the older Originals with the 350w plastic-cased Bafang G060? What you are describing sounds exactly like one of those bikes, including battery size, controller output and brand etc. etc.

There are no temp sensors available on this setup as-is, but I did put a surface sensor on my controller and found it was reaching 160 fahrenheit. I opened up an air channel into the battery box, shielded it from dust and used the battery plugin holes and some vent caps to provide exhaust ports. With a straight thru air path, controller surface temps went down to just above ambient. Within 10-15 degrees IIRC (its been awhile).

Zillions of those bikes got the kind of aftermarket upgrade you are describing, including one I had, and they worked great. But as I think you discovered, hub motors have some limits. Still, it doesn't sound like the motor had anything to do with this. You just got unlucky and got a bad KT controller, unless something like a bad connection somehow caused this. I've never heard of connectors turning black while you watch on these bikes :D

You definitely have the right idea with regard to a hub motor being singlespeed and all. But you want to be aware that mid drives have a learning curve to them whereas you can just jump on a hub drive bike and you pretty much already know how to ride it without breaking anything.

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banshee28   100 mW

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

Post by banshee28 » Sep 07 2021 4:05pm

MoneyPit wrote:
Sep 07 2021 10:34am
Out of curiosity, was this a Sondors fat bike? One of the older Originals with the 350w plastic-cased Bafang G060? What you are describing sounds exactly like one of those bikes, including battery size, controller output and brand etc. etc.
So Yes its a Sondors Original, lol. However the motor casing is still stock (350w version), but the inside was swapped with the new 750W motor. Could that have contributed? So maybe a temp sensor would help, or maybe I had a bad KT controller. Now that I think of it, I did exp some weird readings from the old setup where everything was at ZERO, and would never change. Anyway, will take things easy for now and see how they go.

Definitely will learn and research about Mid-drive but I think for a real e-MTB in conditions I would prob like to ride in, Mid-Drive is prob the way to go.

justlooking808   1 mW

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

Post by justlooking808 » Sep 10 2021 4:27pm

i usually have a cheap controller lying around incase something like this happens. can swap the controllers to test and it takes like 5 min. plus, if the controller is broken, i can use the cheap low amp one until new one arrives. :o

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

Post by MoneyPit » Sep 17 2021 4:48pm

banshee28 wrote:
Sep 07 2021 4:05pm
So Yes its a Sondors Original, lol. However the motor casing is still stock (350w version), but the inside was swapped with the new 750W motor. Could that have contributed? So maybe a temp sensor would help, or maybe I had a bad KT controller. Now that I think of it, I did exp some weird readings from the old setup where everything was at ZERO, and would never change. Anyway, will take things easy for now and see how they go.

Definitely will learn and research about Mid-drive but I think for a real e-MTB in conditions I would prob like to ride in, Mid-Drive is prob the way to go.
So many people did that conversion with no issues, I think your experience was a fluke. Sure an alloy casing would seem to be better, but it sounds like you found your problem and it was the controller.

I stopped messing with hubs some time ago in favor of mids. They're just more versatile. With that said, there's a lot more to screw up on a mid drive build. Also if you are running city streets that are reasonably flat, those G060 hubs are great mated to a 35a controller and 52v..

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

Post by Chalo » Sep 17 2021 5:50pm

MoneyPit wrote:
Sep 17 2021 4:48pm
With that said, there's a lot more to screw up on a mid drive build.
You can get everything exactly right, but a mid drive bike will keep screwing itself up. That's it's nature.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

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