Finding and Replacing Blown Motor Controller Mosfets

In this video Phil illustrates the process he uses at Grin for identifying and replacing shorted mosfets in an ebike motor controller.
Mosfet usually fail when they have to deal with sustained high amperage that generates more heat than they can dissipate. They can also fail from exposure to excessive voltages on the wrong pins or electrostatic discharge.
A well engineered controller will use temperature sensors to limit the current through a mosfet if as it overheats to prevent a catastrophic failure in use, but many systems don't have this intrinsic protection and instead on the motor and bike parameters to generally not overstress the component in normal use. As a result, it's not uncommon for people who push their ebike systems to the limit to find themselves dealing with mosfet repairs in the process.
When they fail it is almost always in a short circuit. On a bike with a direct drive hub motor this results in a heavy cogging and chugging whenever the wheel is turned.
Fortunately a repair is often possible as Phil shows. If it is only one mosfet that is blown, the odds are good that a mosfet replacement alone will fix things. But if both the high and low side mosfets of a motor phase our blown, then that usually indicates damage that has also propagated down to the mosfet drivers and other components, and the odds are lower that a mosfet replacement alone will fix the controller.
There is more ebike troubleshooting information available here
www.ebikes.ca/learn/troublesho...

[@siaseeds8950]

Dude. We need more humans like this gentleman on this earth. I have a Blix Vika+ that failed on me and I called the manufacturer. Talking to them was about as useful as talking to a sack of potatoes. This dude knows exactly what he is talking about.

[@ncm805]

Thank you for the video! Helped me find and switch out a bad mosfet that went bad after a month. FWIW the replacement part for mine was IRFB 3607. Mine also was a negative mosfet but different location than in the video. Moving the mosfet back and forth until it broke off made it a lot easier to hold one leg with pliers and then heat it on the back side until it could pull out. Cleaned out the hole with Chem-wik, right stuff for the job, and in with the replacement. I was able to isolate the correct phase wire by disconnecting each phase wire in turn while rolling the bike backwards. Once the correct phase wire was disconnected, bike rolled backwards easily. Prior to that rolling backwards required more effort indicating a problem (as well as an E9 error code) Bravo - Thank you for your instructions!

[@Cyberbikesau]

Great repair guide. Justin and the team from Grin Tech are the best in the industry!

[@abood533]

Many thanks for the nice video. The way you described the symptoms at the beginning is perfect. Now I can fix my bike thanks to you

[@goodvibes0101]

Oh yeah I have just come across GRIN channel and viewed a few of the content all worth the time so subscribed to validate my appreciation 👏

[@bspalteh]

Thanks for putting these videos together, very useful!

[@maukaman]

Super helpful video! Lots of good information for working with mosfet controllers in general. Thanks!

[@46B3x2you]

thank you so much. Good Job. You just made a horrific challenge into a simple fix.

[@81formann]

If possible, its often easier to cut the legs and remove one leg at a time. Might not save everyone a lot of time in cases like this, but its safer and easier for those unskilled or working with less than ideal tools. A weak 15W soldering iron or an oxidized tip might end up taking too long, and before you know it the traces just come right off the board. Nice video. Blown FETs is a common problem and fixing it is something most will be able to handle. Especially if they have some soldering before.

[@jeffreymorrison2208]

good video, the diagnostics in the beginning were helpful. I would recommend replacing the heat sink compound or at least mentioning it as this is very important in an electrically isolated heat sink. also, the wattage of your gun is important with mosfets as a lot of heat is sucked away by the large traces and the center leg. probably would have fallen out if your gun was hotter. :)

[@antoineboutier8837]

This might be the problem I have with Urban Drivestyle bike. Extremely helpful video.

[@pietypereira8239]

Thank you for the great video. It was a big help.

[@doni20091]

Boa tarde Amigo .super legal .parabéns por compartilha seus conhecimentos. Vou ver todos os seus vídeos valeu td de Bom..

[@donl1411]

Awesome video, didn't realize these could be opened up. Tried on my Aventon, got the end covers off but its sealed in a clear,flexible material.

[@GrinTechnologies]

Some controllers are potted which makes things like mosfet repair a lot more challenging. But first you should confirm if you do actually have a blown mosfet, using the technique in this video or just by plugging it into a motor and spinning the motor with no power applied to see if there is heavy chugging resistance that goes away when the controller is unplugged.

[@donl1411]

On my Aventon the mosfets are ok but the speed is not displayed on the unit & I'm getting am E30 error. Spoke to Aventon & they thought the controller is bad so I thought I'd open it up to see if it was something obvious.

[@dgb5820]

Outstanding easy to understand video

[@34Merlin]

Thanks so much this helps I have two go out on me and the comment on the movement of the tires helped that is what caused my issue

[@TeamHeapMI]

Exactly! Every time I searched what the problem was nothing could give me anything related to my issue

[@marcumkelly2321]

great video help me sort my problem out the best .

[@ajikatakusa3255]

Thanks for your tutorial lesson

[@evil17]

Great vid and info. Thanks

[@DavidMartin-wq5pn]

A great vid learned a lot. Maybe I can get my Charly (from Germany) going now. Thanks

[@sidsnot7850]

Excellent educational video but would have liked to see the heatsink compound replaced.

[@rickc2222]

Thank you so much for this. I'd love to see more on electronic repairs - i have a couple chargers that need diagnosing/repair.

[@GrinTechnologies]

Chargers are trickier if there is an actual component failure, but we've seen quite a few fail from fatigue cracks in the PCB traces where heavy components (capacitors, transformers) were soldered but not held down with a glue or vibration absorbing compound. When people carry the charger with them on their ebike, it's exposed to a lot of vibration.

[@rickc2222]

@@GrinTechnologies Ah, so sometimes just re-soldering all the joints might fix?

[@manFromPeterborough]

@@GrinTechnologies SMPS supplies can be PITA to fix, I once blew a VCR up when my DMM probe accidently touched the drain lead on the chopper FET, after that replacements FETs got destroyed, the TV tech told me the oscillator wasn't switching in/out, I ended up junking that VCR (NEC VN65) Daewoo rebadge

[@tomassimaro6795]

Helped me a lot, thanks!

[@hjeffwallace]

I’ve only built 2 ebikes, but have already replaced 2 controllers. Now I’ll see if I can fix them!

[@al-ayoungentstailorfasalia651]

Very nice work

[@eddiebuckelew]

Thanks for this. Helped me diagnose a bad mosfet in my daughter's hoverboard. Unfortunately, I'm unable to identify the mosfet, so I can't get a suitable replacement. Either way, now I know what the problem is!

[@thekillerdog5228]

Now you can show her this comment as a memory! 🎉

[@DeleteWorld]

Thanks a lot! Keep doing like this! :)

[@edwarddeal6948]

Awesome video. I'm learning more and more about these ebikes. I'd rather fix my own bike rather than pay someone esle to do it . And sometimes you gotta draw a line between what to fix and what to just replace

[@GrinTechnologies]

Controller mosfet replacement can wind up on either side of that line. Very few if any businesses would find it worth attempting these kinds of controller repairs since there is no guarantee of success and they need to pay staff and technicians regardless. But if it's your own motor controller that's blown, then you don't have much to loose from trying and that's what we want to encourage!

[@46B3x2you]

@@GrinTechnologies True to a company that holds true to providing reliable customer service. Nice!

[@stonecoldkill40stinecoldki54]

Great video I appreciate brother!

[@stevemcgowan3017]

its the yellow phase wire on power resistance test thats zero reading on negative test it starts off zero then slowly builds up to the other phase readings or up to 5kohms.i have my old 48v controller will try that soon im just waiting for some jst sm connectors to connect hall sensor back up .steve in uk

[@dein2rad735]

Sehr gutes Video!

[@goodvibes0101]

Nice instructional content good job but I always reapply heat sink compound to new component 👍

[@urbanpuma9136]

Fantastic! Very helpful. Do you have a video for checking 5v regulator transistor in the controller?

[@itsaustraliadayeveryday7234]

Thanks Phil did me well

[@lenkasendecka183]

Great video. I have the same controller as in the video and my motor just shudders and then stops when powered up. I get about 5 kohm's between battery -ve and 2 of the phase wires but only 1.8 kohm on the 3rd phase wire. Is this too low and could one of the mosfets be my problem? Resistance builds as expected on all 3 pahses against battery +ve. I've checked hall sensors and windings on motor itself and they are all good. Thanks for any help.

[@gideonashby1594]

great post thankyou for that the share!

[@sausagefingers714]

i just taken a reading on all 6 of my mosfets.. 2-6 all have a climbing voltage reading. but number 1 has a voltage spike on first contact and then begins to fall? is this the problem im having? when the system is live, its feeding 5v to all phases at the same time.. even when i apply the throttle, the voltage on all phases just sags to 0.3v and the motor makes a tiny humming sound.

[@EBIKESBR]

obrigado por compartilhar seu conhecimento!

[@DPRKGrandmarshal]

great video!

[@nuwansandaruwan4334]

Hey Friend thanks showing us , my scooter have problem at starting switch I replace one , but it not working, my friend told me the control, it’s? Can u help me please

[@MKxSylOiZ]

Thanks for this great guide, the biggest problem to find the right china mosfet, in my case it is a brainpower control. DC52V (the scooter is a Speedway 4 clone + no dualtron 1x800w motor) the mosfets(to 220) have the designation: K M ..9Y ....... 19x 2452 ..... L12 .... K3475N .. Unfortunately I could not find a data sheet to find comparable replacement mosfets. does someone have a tip?

[@DallasAya]

Cool video, I think you may consider wearing a bicycle helmet with alien blinking strobes for theatrical effect

[@roncooke2188]

Nice video interesting, just replacing a faulty mosfet, don’t know what solder they used but quite a job trying to melt the solder with very hot iron

[@GrinTechnologies]

Most controllers are made to be RoHS compliant for the CE sticker and so are using lead free solder, which yes is a PITA to melt and work with. Use flux and use the hottest iron setting with the largest tip. When you resolder on new mosfets you can use the much easier to work with lead/tin stuff.

[@jesp999]

Im trying to diagnose my nanobot d4+ 2.0 scooter. This problem does not happen in the cold morning on my first ride but happens in middle of day when it is warmer. Im in NM. What happens is both motors cut out when I'm in dual mode and when i go full throttle, and also sometimes when i try to just accelerate quickly. when it cuts out i does not come back alive by simply backing off a little on the throttle but i have to totally go back to 0 or no throttle and then the motors start if i re-engage the throttle more gently incrementing the speed. It does not happen in single mode when in just rear hub drive. When in single mode i can press the throttle fully and as quickly as I like. If I think of the thumb throttle as a clock that goes clockwise from 12 to 6. it is at the 5 when the motors cut out. It also happens if i got from 12 to 3 very very quickly. I'm pretty techy and i can replace of fix most anything but I like to diagnose first. I did have an extra thumb throttle speed controller so i did decide to replace that (because a year ago i brew out its usb power port when making a dual charger for a camera i have) but changing that speed controller had no change in the symptoms. Do you think there is a short somewhere in the system on full power or is it a hall sensor. Is it overheating and the bms cutting out? There are two controllers in the scooter with a communication wire between them, could one of the controllers be off. Both motors shut off when this happens. What tests should i run to see where the problem is? I have opened up the scooter before because I silicone sealed everything to protect from water. but actually moved to NM where there is little rain and I do not ride it in mud or water anyway. Any help appreciated.

[@bionicblitz171]

shorted yellow phase of sabvoton to positive. replaced fets but the power light wont even come on... help? will pay for a working soloution

[@trevorjames5493]

Hey thanks for the video it helped me do some troubleshooting just had a question for you so if I'm getting continuity from battery positive to two out of the three phase wires, and continuity from battery negative to the third phase wire, does that mean all 12 of the mosfets are bad? I'm also getting continuity from the positive battery connector on the board to the battery negative on the extension cable for my battery. So let's say I changed all 12 mosfets would that fix the problem or would I have to find what the problem was in the first place before I change them because they might get shorted again? It looks like some of the mosfets actually have a crack in their leg maybe they're not fully connected on the one leg there's three legs on each and about 6 out of 12 them look like they have cracks in the solder but no signs of burning or anything and the rest of the board looks okay except for one capacitor that is not swollen but it looks like it's caving in a little tiny bit. When capacitors go bad is it possible for them to cave in instead of pop up swollen? Thank you in advance for your time!!!

[@robert71457]

Good stuff maynard!😁

[@stevemcgowan3017]

hi i tested my controller in resistance mode like your tests and one reading is zero on red power side does that mean mosfet blown?controller not that old from alixpress 48v 1500watt on a 1000watt hub motor and 54v 18650 samsung.had throttle problem before so bought this new controller and throttle kit.lcd display lights up ok had last ride and motor died and seemed to run rough the wheel with motor in.ride before that was intermittment power.

[@nettuananh]

Hello, how to remove speed limit on xiaomi himo c20? Thank you very much!

[@5jazzman]

Great video, very well explained. Here's what happened last week, after a heavy rain my ebike died, the display doesn't turn on anymore, so I decided to check the controller. Doing a resistance test I connected each phase wire with the negative probe while alternating the positive probe with the positive and negative of the power inlet. From each phase wire the negative gives 0 while the positive gives 18, should I conclude that all negative mosfets are blown? Please help :(

[@bobravenscraft5376]

Buy an xtra cheap controller

[@lukewalker1051]

Nicely explained. Many thanks! PS. I own some Grin products. Great, innovative company.

[@GrinTechnologies]

Thanks Luke! Glad you found the video useful!

[@roncooke2188]

Good video how do we know if we have the correct mosfet

[@mscir]

Great video, thanks. Is there a procedure for the Baserunner Baserunner_Z9 ?

[@roncooke2188]

I have an ebike just come in been standing in his shed 6 months, has no light on display, battery is good fully charged all wiring and connections are controller connections all good bike is only 18 months old , any pointers please ??? could be controller but all looks new condition

[@stephen8385]

i have a minimotors controller shorted because the accessories wire positive and negative touching, i tried replace the fuse but lcd only turn on for split second, motor also a bit weird when spinning by hand, but if i unplug the yellow wire motor turn smooth by hand. any idea how to fix it?

[@douwesteen]

Thank brother you saved me!!

[@globalwarming5050]

how to tell if a mosfet is bad for a treadmill? will the same apply if the treadmill motor is showing resistance if you spin the belt by hand?

[@dr.moustafaibrahim6810]

Thank You for the video

[@GrinTechnologies]

You're welcome

[@flow0125]

Hi I have an electric scooter I connected it to the battery indicator and it made me short-circuit the whole indicator works the lights the brake lights the horn everything except the engine you think it is

[@billyjenkins3015]

I have a 48v Brushless Razor mx650. My problem is the motor only runs when you rotate the drive gear to a certain point. Do you think I might have a bad mosfet in my controller?

[@roamingeyesvision]

What will be the result if I replace 85v 150A mosfet ( k150e09ne- 18 nos) & 63v caps with 100v 200a (SSF1006 mosfet) & 100v Caps. Controller is 48v 45a...

[@odoohub5010]

What causes the mosfet to fail? is a lesser amp controller more likely to fail than a bigger ah controller?

[@pietypereira8239]

The pedal assist wiring shows positive +5V and signal wire + 4.6V. Please any help. What can I replace? The throttle works fine. Except the pedal assist not working. Please advice.

[@Bergwacht]

my battery cable fell of so the kers burned anything on my controller. sadly i dont think that replacing mosfets will help if the esc just does nothing anymore, even the scooter doesnt turn on anymore. I have a functioning replacement controller but it's from a german 20 kmh m365 clone, and just the tail light flashes ... so i have to replayce broken parts but what for parts?

[@AndreLuiz-ip3fh]

Isn't better to change all the 6 Mosfet? Even using an higher current model?

[@TnTckoo]

Hi dude, i have bad controller, but i check 3 phases and there is no problem. So i try check resistence betwen mosfet legs and i find one with diferent resistence - shorted circuit with no resistence. you think that mosfet is broken? And when is 80V/170A i need stick with these volts and amps or can be different? how much if yes? 75V/160A? Rds same or lower and Total GATE charge same or lower? thats all what i need to know when replace this mosfet? thanks dude

[@jcreedy20]

Could have just unscrewed the heat sync and snipped the mosfet legs and pulled them individually. If youve got a nice chunky head on your soldering iron then its easy enough to pull it as a whole chunk. I liked the diagnostic method you used for finding the bad fet.

[@jorgedelagarza7611]

Thank you! Question, which control is this?

[@viynmobility3121]

My controller has two wires each for the brakes(the brakes are on when i short the wires of one brake) and i want to use one of the brake's wires with relay to control with arduino is this possible ? If not what should i use?

[@deftrover]

Thank you!

[@darrellwhiteman6190]

what does the letters and numbers refer too on the solder side of the controller

[@cliffwisser9077]

Thanks Phil for the video. I have identified several blown Mosfets after seeing your video. I have a chinese controller with 12 Mosfets. No markings to identify them. Can you tell me what Mosfets I need, and where to get them? I have a 48V, 26amp controller.

[@kevmatt8450]

good luck

[@user-nk5xi6lj6f]

I've got same issue, I've established the issue is on yellow phase however my multimeter is ancient and has no beep noises... what should I be looking for on screen in terms of finding the offending mosfet? There are 5 per phase on my controller

[@christothegreat1]

What if any is the risk to replace only the 2 blown mosfets out of 6, with ones that are quite close in values V, A, Rdson?

[@Mr.Whites_Forex]

great vid

[@rajendrarajput5906]

hey! how can I find the rating of the motor controller if the label removes from the motor controller mosfet? is there any way to get this number using multi meter ?

[@roncooke2188]

Thank you

[@tapsmith339]

I bought a lot of vailride scooters from action and i can not get them to go. Is there a way to solder a bypass on speed controller. If anybody can help me with this I would appreciate it. Thanks

[@ziadfawzi]

Thank you.

[@ibbredeh777]

Hi please can you look into my case I got about 6 blown controller I watched your video and tried to fix by testing if any mosfet is bad just like one of your video but luckily all are good So what do you think is the faulty parts . Note some of them are reading high voltages more than as it should Please guys I need a help to.

[@Jrobt3223]

Hi there. I put one of these bikes together for my son. It was so cool I decided to put one together for my self. I am 60 years old and have a three miles of hill to climb to get home from the flat lands. My son and I decided to take a ride the next day after I put mine together. We were out about seven miles and mine quite. I shut it off and then turned it back on and it went about a half a mile and then it blue a fuse. I put in another fuse it blue that one to. I did what you said and checked out the wires and the blue one went to ground. I pulled it apart and there’s 12 of these mosfets . Don’t know what to do now. Some are positive but not like what you show. I’m stuck

[@seahawks1185]

Sounds like the controller fuse can't handle the battery voltage, whats the controller rated at and whats the battery voltage? A 48v battery charges to around 54.6v - Controller fuse should always match the battery voltage.

[@ramkatyal277]

sorry mate i dont have reading on any phase with positive conector, any idea?

[@northernlits425]

your work bench is making me claustrophobic man!

[@killack4944]

Hi, I have a question to ask. Today I was going to charge the battery of my 72v 40amp 8000w and once I plugged it it short circuited, are you able to tell me what is gone? So I turn on the scooter and the volt meter on the scooter is going down really really fast? Can you help me? Thank you Sir

[@abood533]

I have a question about the replacemnet Mosfet. Should it be exactly matching the old. Or I can use something with in range? I have 6 mosfet controller 32V, 250W controller. Can I use 49A 55V Mosfet?

[@GrinTechnologies]

In general it's a good idea to try and match or do better for the Rds ON resistance, and also the total gate charge or gate capacitance. Both or these specs are well documented in the datasheet for any given mosfet model. What you don't want to base in on is nominal amperage. Saying 49A doesn't mean anything really since the current handling depends massively on the extent of heatsinking, you want to look at the fet's actual electrical characterization.

[@sdiburro1]

I have a swagtron envy bike I think the motor is only 200 watts it has a small motor controller in it. I was having problems with it when I got a 14 amp battery at 36 volts that battery that came with it was only a 4.4 amp battery at 36 volts mine keeps cutting off the power and the display malfunctioning going crazy then I noticed the controller was getting hot is it because the battery has more amps in it how will I lower the amperage do you think I might need a new motor controller

[@garyosgood7499]

Can anyone please help me with a faulty e scooter? Every time I go to charge it up it shorts out the battery charger. The battery is actually fully charged, I disconnected the battery from the control unit. Every time I go to connect it back up it blows the battery connectors to bits

[@facelessvaper]

Perfect video major help - thanks - did you ever do a vid on testing hall sensors on a motor with the same connectors as the controller in this video

[@justinlemireelmore]

No, we haven't made a video on this yet but that would be subject of a future video for sure! Usually with overmolded connectors like this, in order to measure the hall voltages you would either make a M-F connector splice that brings out the hall wires to probe, or you would open up the motor controller and measure the voltages directly on the controller PCB. This is one case where the JST plugs are a lot easier to work with.

[@facelessvaper]

@@justinlemireelmore Inspired - thanks - I have spares that I could try and make a F connector, my connectors are "julet" or higo style - As my kit is new opening the controller and motor to test internally is no-go for me. I have a medium level of vibration from the motor felt from the seat when setting off or changing PAS levels for hills, it always seems to be when torque is needed, once over 12mph everything is smooth, how I explain or show the Chinese company this is the next question or maybe this vibration is normal for a rear setup, my first 2 motors were front hub.

[@camilorobles2433]

@@facelessvaper that's because you're using a squarewave controller. it's normal.

[@facelessvaper]

@@camilorobles2433 One year on and yes I would normally agree with you square vs sine, but in my case it was a motor and controller fault, the motor was replaced and worked well with no vibration on a newer square controller. The company in question has now moved away from KT controllers as the were getting numerous faults reported and I personally have moved back to front hub over volted to 48v and, yes are now using a sinewave controller, which like you rightly say is much smoother and overall is a better system.

[@thesmuler5627]

I’m my case the solder actually melted and shorter the source/drain trace. So also look for melted solder sometimes mosfet can handled load but not the solder board. I packed that thing with solder to allow more current

[@hawaiirealtorandrewellis4701]

Somehow I managed to Burn out 2 new controllers when just hooking up to the battery. I get no readings back when testing positive side, only negative side readings. And when putting the leads on both Positive direct to Negative I get nothing. Ever heard of this? New 60v battery is putting out the right current. Controller is supposed to handle up to 72v and 45amps 2000-3000 watt motor. Briefly worked but after unplugging and plugging battery to controller a few times with a decent spark at connector it fried the first one so I tried the second controller thinking it was a fluke and same thing. Ugh! Any thoughts? Hate to see this happen again. I'm going to get a spark resistor for the next one but sounds like that likely isn't the problem? Thank you

[@teemck9921]

Hey good video can you advise on whats best i recently have a fault with my scooter it powers on ok, the issue is that it won't accelerate and the brake light stays on, i have checked everything cables, battery charges ok the only thing is the controller or the motor hub i followed your video checking the misfets and can seem to find the problem ive checked the internet for a replacement but they all have different end connectors to mine are these controllers standard ? can i replace the end connectors.

[@harryhughes5868]

can you help please, my girlfriend has an old bateribike wich has stopped working. new battery, still not working. we think it might be a controler. can you advise or anyone to sort out, please. Harry

[@jhonny001]

Hi Phil, really nice and helpful video. It helped me find the faulty MOSFET in my controller. However, as soon as I plug the battery connector and try to accelerate, the same MOSFET is failing... I've replaced the same twice... Any ideas?

[@justinlemireelmore]

That usually means you also have a blown or damaged mosfet gate driver circuit unfortunately. and fixing that requires much more specific knowledge of your particular controller PCB. We find that in about 2/3's of cases with controllers that have a blown mosfet it can be fixed just with the mosfet replacement, but about 1/3rd of the time there are problem that have propagated further upstream and replacing a FET alone isn't enough. .

[@jhonny001]

@@justinlemireelmore Thanks Justin! It is a 22A KT controller from Aliexpress... Probably one of the most common ones... The rest of the components in the board look OK... I also tested a couple of capacitors of that same phase...

[@ideafromkurdistan5257]

Good mr. please my throttel not run maybe lost mosfet or short ?

[@kevmatt8450]

Why are all of these videos from over 2 years ago when these scooters are more popular now than ever?

[@Matanumi]

Because thats when these all came out

[@oldskoolhead0]

how does this work when you have 9 mosfets? there are only 2 polarities and 3 phases, though my mosfets are in apparently banks of 3 and there are 2 the same and 1 different in each bank, i am getting shorts accross the power rails and the 3 middle mosfets are all shorted across all 3 pins, the other 6 only show continuity on the middle pin, i am assuming it is only the 3 in the middle i need to change, great info, but a bit of elaboration on if there are more than 6 mosfets (which fit into the + - of 3 phases) would be helpful, cheers

[@GrinTechnologies]

When there are multiple mosfets they are always hooked up in parallel. Much more common than 9 fets would be to have 12 mosfets, where every mosfet is doubled up. With 9, it means that either the high side or low side fet is doubled while the complimentary (low or high side) is single. If the failure is on a paralleled mosfet, you can't tell until removing the fets which one of the two is damaged. The easiest thing to do is just remove and replace them both, but if you remove one first and see that the short is gone, it usually means that the problem was only with the mosfet you took out and the 2nd one can possibly stay in place.

[@johnykool59]

Hi My grandsons xiaomi has stopped working dead. The video you made has been a great help as its the first time working on these. The connector to the motor has melted so I presumed there's a short in the wiring or motor. Could you please confirm i am on the right track with that. Thank you.

[@GrinTechnologies]

Usually a melted connector is not the result of a short anywhere but simply the result of too much current through the connector for too long. First try just bypassing the connector and hooking up the wires directly to each other to see if it otherwise still works fine, odds are good that it will.

[@gigicontra2447]

hi,i have a problem with my ebike,battery is draining fast around 10miles range also when i put the battery on the bike it makes sparks at the connectors,i replaced the battery pack with a new one but still doesnt go more than 10miles ,im thinking it has a short but how can i test it

[@rockefelleragent1357]

Can the mosfets overheat and be blown too?

[@RoySATX]

Pretty good. I'd have applied new thermal paste, at least to the replaced MOSFET, and cleaned the flux off the board, both would add life to the controller which is, after all, the point of this exercise. Maybe you did, but you didn't mention or show either before stating it was finished and closing it back up.

[@GrinTechnologies]

Yeah the best thing is actually to replace the kapton tape strip with an ACTUAL thermal isolating pad that has much better thermal conductivity. The cleaning of flux residue doesn't have any consequences one way or another.

[@antorchabikes]

Hi, excelent video thanks a lot. i have a question. i have a controller that PAS works fine but throttle doesn't. i already tested throttle in another system and works fine. also made this test (fase and + or -) and it is working fine. do you know what more test can i do to the controller?

[@46B3x2you]

There may be two blue wires that connect together and cause the controller to limit your speed to 20 miles an hour. If you disconnect those two blue wires. You will be able to override the 20 mile per hour limit.

[@harryhughes5868]

Hi my girlfriend has an old bateribike which stopped working. we have tried a new battery , no goog we think it is the controler, ? any help would be good. Harry

[@antorchabikes]

@@harryhughes5868 hi it could be several issues. i teach in my channel how to try step by step, sorry it is in spanish! kzbin.info/www/bejne/Y168lHSJmrGphKM