Further info needed on repairing controller

[minexplorer]

Hi,the situation i described in a previous post was this. Fitting a watt meter i carefully tweaked the shunt to give 17-18 amps on full.Ive ridden a couple hundred miles,with plenty of 2 mile long hill climbs at 17 amps all the way. Not once did this cause any overheating of controller or motor. Then one time i rode a mile on flat terrain,stopped.Then when i went to continue,all i got was a hum and a brief twitch from the motor. The caps are 50v ,the fets 60amp continous max.
I discovered one fet had blown. I replaced it ,then noticed a tiny black component nearby was split and surrounded by a smoke stain. Its black 2mm x 4mm ,marked Y2.Ive identified it as a ZENER DIODE. Well without much hope of it working ,i connected the battery anyway.There was a bang and the replacement FET instantly burst into flame. Fresh smoke staining around the diode apparent.
Can anyone tell me, have i pushed the controller amps too far,its 18 absolute max,usually 17 - 17.5 ?
Did the fet blow because the diode failed or vice versa ? Is the diode likely to have failed because of the increased amps,or just fatigue ?
Im trying to get an idea if replacing the diode and fet will get things going again.Or will it likely wear out again ,due to the amps being too much for it ? I like fixing things if theyre not too far gone.Its good experience. Thanks if anyone can enlighten me.

 

[Nealh]

I have shunt modded 3 of my KT's and all are working without any issue, admittedly they are the dual voltage models so may have slightly better component's. Being extra careful with the solder is important as any slight splattering or misplace dsolder will cause issues elsewhere.

 

[wheeliepete]

Minexplorer, didn't you have a blob of melted solder on the board near the shunt? Could of caused some other damage.

 

[minexplorer]

Minexplorer, didn't you have a blob of melted solder on the board near the shunt? Could of caused some other damage.

when i got it up to 20-21 amps the solder did indeed melt a little,but just settled around the bottom of the shunt legs .I removed it and didnt have a reccurence at 17 amp .That was ages back too,an no where near the diode thats blown. Im just wondering if it was just age or something made it fail and that then caused the fet to blow.

 

[footpump]

that was me as well solder melted and fell on cboard, yosepower/elife shop rear 350w with supplied 15amp controller, did shunt mod, added too much solder I believe.
a few hills ok, a real steep one at slow speed , all stopped fried controller mosfet.
new controller all ok.

I have ordered a kt 36/48 350 dualvoltage 6 mosfet 17 amp controller from psw power if I can fit it , have spare non jullet throttle/pas/ and hope to use with led 890.

replacing a mosfet looked a bit daunting so did not attempt is there a vid on how to

 

[minexplorer]

that was me as well solder melted and fell on cboard, yosepower/elife shop rear 350w with supplied 15amp controller, did shunt mod, added too much solder I believe.
a few hills ok, a real steep one at slow speed , all stopped fried controller mosfet.
new controller all ok.

I have ordered a kt 36/48 350 dualvoltage 6 mosfet 17 amp controller from psw power if I can fit it , have spare non jullet throttle/pas/ and hope to use with led 890.

replacing a mosfet looked a bit daunting so did not attempt is there a vid on how to

ive considered getting a kt 17amp controller.But also like to mend stuff. Replacing a fet s easy enough.Mine didnt blow on a hill tho ,wasnt under any stress at the time. You did indeed prob add too much.I used the watt meter display to tweak in increments .It was well in safety limits of the design

 

[Nealh]

FP soldered the wrong shunt leg, the solder melted and shorted other nearby circuitry tracks which were close to the Fets.

 

[Deleted member 4366]

I must have modded around 40 controllers altogether. I normally stick to 19 amps or below, but i have gone as high as 22A without any problems. I've never blown mosfets, though I am quite careful to not let the motor labour at low speed, which heats up everything.

Zener diodes are important because they're normally used to regulate voltage.

 

[minexplorer]

I must have modded around 40 controllers altogether. I normally stick to 19 amps or below, but i have gone as high as 22A without any problems. I've never blown mosfets, though I am quite careful to not let the motor labour at low speed, which heats up everything.

Zener diodes are important because they're normally used to regulate voltage.

i dont honestly think the modding caused this d8veh.It was under no strain. Looks like the blown diode caused the fet & the replacement to fail ( the replacement quite dramatically) . Does this seem reasonable? It looks very hard to replace, its so tiny.Have you any idea what may have caused this? Thanks

 

[Deleted member 4366]

It's impossible to say which component took out which. MOSFETs can blow for simple reasons, like a loose connected phase wire. People feel the motor start to stutter, so they give full power in an attempt to clear or override it, which is often fatal for the controller.