Paul & Sabrina's cheap DIY 144v motor controller

[blacksun1989]

So my controller works now. Great and thank you paul for all your help. But now i have another issue. So i want to use my Original Gas-pedal its already an electronic one. But now i have the problem it starts at 2.42 Ohm and goes down to 1.9 ohm. Is it possible to use it with that controller? because i tryed it but i cant configure it. When i enter for throttle max 166 and for throttle min 296 it just does nothing. And if i have it on the basic settings and i move the pedal i can see the red trottle bar going up and down for a little in the rtd explorer...

[MPaulHolmes]

Originally Posted by blacksun1989

So my controller works now. Great and thank you paul for all your help. But now i have another issue. So i want to use my Original Gas-pedal its already an electronic one. But now i have the problem it starts at 2.42 Ohm and goes down to 1.9 ohm. Is it possible to use it with that controller? because i tryed it but i cant configure it. When i enter for throttle max 166 and for throttle min 296 it just does nothing. And if i have it on the basic settings and i move the pedal i can see the red trottle bar going up and down for a little in the rtd explorer...

Do you mean that it goes from 2.42v down to 1.9v? In that case, you would set "throttle-max-rc" (or whatever the heck it's called) to anything LOWER than 495. I'd try 485 to allow for some dead zone for zero throttle. Then set "throttle-min-rc" to 389.

By the way, 495 = 2.42volts/5volts * 1024, and 389 = 1.9volts/5volts*1024.

The 1024 is because the A/D converter is 10 bits (2^10 = 1024), and it's on a scale of 0 to 5 volts. 0 volts corresponds to an A/D reading of 0, and 5v is 1023. oops, I used 1024 above. haha.

-Paul

[MPaulHolmes]

I had an interesting failure of the DC test controller. I bumped up the voltage to 144v, precharged the capacitor bank, verified that the bank was full, and then removed the precharge resistor. I figured it would be safer to do a test just with the energy stored in the capacitor bank, not directly hooked up to the batteries. I had changed the code so that twisting the throttle to 100% corresponded to only like 6% duty, just to be safe. I gave it a tiny bit of throttle, and the gate to source signal on the oscilloscope looked perfectly clean. I turned it back to 0, and found that the capacitors were discharged. I tried to recharge the capacitor bank, but the mosfets had failed shorted!

[apowers]

Hi Paul

I see you pre-charged the caps checked the voltage then removed the resistor. Was there still voltage on the caps then? If not then one of the MOSFET's may have already been bad. It could have been damaged from soldering. Or bad right out of the box.

Mine is still working. It has been in use for over 3 years.

Thank You Very Much

Alvin

[MPaulHolmes]

I verified that the caps were at around 145v, and falling slowly due to some leaking. Then as soon as I gave it some throttle, the mosfets were failed shorted. Maybe I should do an experiment with some exotic solder that melts 140 degC or something. Maybe they don't like the thermal shock of going from 20degC to "really hot" to 20degC in like 5 or 6 seconds.

[apowers]

Maybe pre-heat them in the oven. Is this the controller with the mosfet's attached to the bus?

[MPaulHolmes]

Yep, I heated the bus bar, and stick the mosfets on, and as soon as the middle leg (connected to the back of the mosfets) gets to solder temp, I submerse the bus bar in water. The whole process only takes maybe 6 seconds, and the bar is less than 500 degF. The datasheet says the mosfets' legs can be at 500degF for 10 seconds, but it says nothing about the back metal heatsink. The diodes have never failed. I think you are right about preheating the mosfets too.

[MPaulHolmes]

I remember when Joe (yanof) was telling me that he tried the cincon as a high side power supply for a charger, and it worked for low voltage, but not high voltage. Maybe I screwed up the isolated supplies. I did pick the cheapest possible line filter. I know for a fact that if I use a powerex isolated 15v-15v dc-dc converter, that an isotop mosfet switches just fine at high voltage. That's how I did the charger... So, I could try the powerex dc-dc instead of my isolated dc-dc. It may not be a problem with the soldering at all.

[jyanof]

Originally Posted by MPaulHolmes

I remember when Joe (yanof) was telling me that he tried the cincon as a high side power supply for a charger, and it worked for low voltage, but not high voltage.

yeah, in my application, the high barrier capacitance in the DCDC caused the micro to lock up, but the fets were still fine. it was really weird, but using the powerex dcdc solved it.

would you be able to rig up some way to clamp the mosfets to the bus bar for a quick test instead of using solder? That might be a quick way to see if the soldering was the problem. Just add a little thermal grease and maybe just weigh them down with something heavy. You probably won't be able to go to as high of currents, but if it still has problems, then that rules out the soldering...

[Roche]

fwiw

It may be worth baking the mosfets for 24 hours prior to soldering at about 30-50C - that helps get rid of any moisture the package may have absorbed - it's a reasonably common procedure. The cooling probably shouldn't be more violent than a cool air blower; too bigger dT/dt can be quite damaging, due to differential coefficients of expansion. (or contraction)

Regards,

Roche