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[greasypants]

Got all the parts and started putting my bike together this past week . Rear 5304, 72V 35a controller , 2 x 36v 18AH nimh packs from ebikes. Tested @ 36V to make sure everyhing worked while I built a box for the second battery .Rode around the neighborhood a few times last week and everthing worked fine . Today I finished and mounted the battery box for the second battery and tried the bike @ 72v . Road up and down my short street a few times at 1/2 throttle and everything worked fine , then went full throttle and after a few feet the bike quite . Figured I blew a fuse as I could only find 30 amp fuses to fit the fuse holders that came with the batteries. Checked the batteries and sure enough both fuses had blow; when I replaced the fuses the bike lurched forward and blew one fuse immediatley even though the throttle was at zero . Tried running just one battery at 36V and same thing happened . Looks like the controller is stuck @ 100 % throttle . I removed the end plate of the controller and didn't smell or see anything melted . Anyone know what the problem may be ?

 

[lemmiwinks]

Sounds like a shorted MOSFET in your controller.

 

[fechter]

Sounds like a shorted MOSFET in your controller.

Sounds like that to me too. I hate it when that happens.

Try disconnecting the motor phase wires (the fat ones) and use an ohmmeter to measure the resistance from each phase wire to both the main red and black battery wires going to the controller (six combinations).

If any of these measurements are zero ohms (or nearly zero) then you have a shorted FET. More than one combination might read zero, telling you how many FETs blew.

 

[xyster]

QC issues bite. I have the same controller paired to the same motor and it's held up just dandy for 3 months now at 84 peak volts.

 

[knoxie]

Yes

Its luck of the draw as I have one that works fine at 72V and others that blow. I am out of action for a few weeks but will have a modified controller to help sort this problem out.

You will have almost certainly blown a fet, I have heard so many problems of these controllers blowing at 72V, Has anyone told Kenny? the new 150V mosfets should make it a lot more reliable at 72V.

Do the tests Fechter mentioned it will tell you all you need to know, I have blown a controller at 72V under no load, there is an issue with these controllers at 72V and it is a reason certain vendors sell them as 48V controllers, good luck and if you got your kit from justin lets us all know what he says.

cheers

knoxie

 

[fechter]

Hopefully you can get the controller replaced under warrany.

I'm not convinced it's the actual voltage that blows them. At higher voltage, they have to take more amps and dissipate more power. I think the dissipation kills them. I'm also suspicious of the stock FETs, even though they are made by IR. Like Knoxie says, some can handle it, while others can't. Maybe they get a discount for "factory seconds" or untested parts.

They just need to start making them with IRFB4110's :wink:

 

[knoxie]

I agree Richard

I think they are using poor quality fets, I think you are right the higher voltages may be exposing them, i dont think it is thermal as i have had them blow in a second under no load and my kmx controller runs really hot at 72v under load and has been fine, i think they have got some bargain basement fets in some of these controllers.

I wouldnt want to change all the fets in more than 1 or 2 as its very time consuming. I will beef my ones and maybe a couple more, but thats all, kenny should get this sorted.

Knoxie

 

[Ypedal]

You guys are makin me nervous... I have a shipment of parts on the way from Kenny....

Good thing about this is that i will PERSONALLY test every single motor and controller before shipping to a customer... i see no other option. Better to get a " Used and tested " part than a " might work but brand new " ... As long as i'm not selling large volume . i will afford the time required.. even if it delays a shipment by a day or 2.

 

[greasypants]

Thanks everyone , did the fetcher test and one showed zero , and three of them didn't move the needle at all. Waiting to hear back from ebikes. Wonder if its better to just replace all the fets or roll the dice and try another one , hate to get stranded somewhere with the same problem .

 

[fechter]

The fuses probably prevented the usual catastrophic FET blowout and smoke release.

If you can replace it under warranty, you should do it.

If you're real lucky, they won't want the blown one back :wink:

Changing all the FETs to 4110's is a fair amount of work, and the little buggers seem to be in short supply right now, since they beat the crap out of older FETs. This also makes them expensive. 4310's are another option.

There's about a 50% chance that one of the gate drivers also blew. For sure the gate resistors almost always go when a FET blows, but those are cheap.

Knoxie has a thread on repairing the FETs.

 

[knoxie]

Well

I would let Justin sort it, the 72V issue wont get sorted unless the suppliers address it with Kenny, Its a pain but these controllers are generally not reliable at 72V. I will replace mine but its a job and a half, I hope Kenny sees sense and starts using better fets in the controllers. I will almost bet he will drop the rating to 48V on the 36-72V controllers and bring out a 72-100V or a true 72V controller for more dollars! I know how the Chinese work!!

Good luck

Knoxie

 

[greasypants]

Justin has offered to upgrade the fets on my blown controller for a resonable fee. He wants to document it and put it on his website as DIY guide so that should be good for everyone.

 

[fechter]

That's great!

Did he say which FETs he's going to upgrade to?

 

[knoxie]

Yep

Good news, If I were Justin I wouldn't advertise these controllers as 72V controllers until this problem gets sorted, Kenny must sort this one out, we have exposed them as having a problem its not fair on the vendors to have to change them, its a 4 hour job start to finish esp if one has blown you have to fault find and swap out board components usually.

Good luck

Knoxie

 

[greasypants]

The new fets are the IRFB4110's. Lowell had some extra and Justin will buy them from him on my behalf.

 

[greasypants]

The new fets are the IRFB4110's. Lowell had some extra and Justin will buy them from him on my behalf.

 

[fechter]

Excellent!
Those should be nearly bullet proof below 90v.