Paul & Sabrina's cheap DIY 144v motor controller

[duncan]

Hi Paul
A question - the new power board has 3 holes - the hardware I have has 4 holes

I was thinking about changing/machining the hardware to match the board but I am now thinking about drilling some extra holes in the power board - I will need to ensure that the mounting bolts don't touch the copper

What do you think??

[blacksun1989]

Thanks for all the help!
Thanks paul for all the help so far! The controller runs fine and its amazing!
But i still have an question to you. So is it possible to change the pwm frequency? Because electric motors dont all run best at the same frequency. Because i feel like my 11" forklift motor ( rated at 80v and 15k originally) should have a little more torque... So think tis controller runs at around 20 khz and i wanted to try some lower ones...
Thanks johannes from germany

[MPaulHolmes]

Hi Duncan, sorry, I wasn't getting notifications about new posts. The "diode" is actually 2 diodes in parallel, with a common cathode, which is the middle leg. So, there's anode #1 which is leg #1, and anode #2 which is leg #3, and then common cathode (and back of the TO-247 package) is leg #2. So, the middle leg has to carry 2 times the current of the other 2 legs. But it's not the problem you might think. The back acts like a big heat sink, so it's actually much harder to vaporize the middle leg from high current than it is to vaporize leg 1 or 3. It's the same way with the mosfets. The drain leg is usually still intact after a failure, since it's connected to the back.

Sure, you could drill in the power board. You could use those little plastic flange things to isolate the bolt. I have no idea what they are called though. Man, I just bought some the other day... It seems like "bearing" is one of the words. Flange bearing?

Hi Johannes! The puny torque just comes from the fact that it's limiting the current to 500 motor amps. Even at a lower frequency it would still limit the motor amps to 500 amps. You just need more motor amps, and this poor little controller will start to blow up above 600amp. There is an option in the code, however, to run the pwm frequency at 8kHz rather than the standard 15.6kHz.

I submitted the stupid paperwork for the retirement money and now they are doddling, probably waiting until the market tanks so they don't have to give me as much. haha.

[duncan]

Hi Paul

I am starting from an empty board so-
I am thinking of
MOSFETS - Gigamos - IXFK140N25T -
140amps, 255nC, 250volts - slightly more current but 50 more volts

Diodes - SBR60A300PT-ND -
60amps, - 300volts - the reverse recovery is not as good 55nS as opposed to 27nS
Is that a killer???

Capacitors - EET-ED2E681CA
680uF - 250volts,

This would enable me to increase the voltage - ~ 180v??

I would like to increase the voltage as I am sagging a lot - I only have a small pack

2P - 44S of 16Ah Headway cells

I do intend increasing my pack size as soon as I can afford it

So Paul - Is this a good recipe? - would I be able to go to 700 amps? - 180 volts?

A assume I would also have to change the current sensor - and possibly the software

- Changing the subject entirely - Retirement funds?? - I thought you were a youngster - not an old fogey like me

[MPaulHolmes]

Duncan, I think it would work. 55nS is still a very fast reverse recovery. I had a little retirement money from when I was teaching at the college in Olympia, and I'm taking it out. Of course, we won't talk about the tiny fraction I actually get to keep... But it will really speed things up for getting some stuff done that I've wanted to test for a long time.

[type2teach]

Originally Posted by type2teach

Update:
I finally got some time to work on the EV. Now, the EV won't even roll out of the garage at a low speed. It seems like whatever is happening is getting worse. It *starts* to move and then stops. It rolls a tiny bit, maybe half an inch, before the episode starts happening.
So I took the two cables from the controller off the motor and with the controller on and my hand mechanicaly controlling the pot, I measured the volts going to the motor. It put out way more volts than I expected very quickly. It went from 0 to 90v within a very small movement of the pot arm.
But I took that to mean that the controller was responding appropriately.
So I dropped the motor (easier said than done) and with it firmly secured, I used jumper cables to run 6v to it and then 12v to it from my battery pack. At 6v I could barely stop the motor from turing with my hand. 12v was too much to stop, and it sounded like the RPMs were going up and up if I left the cables attached.
There's nothing obvious out of place on the motor, but I don't have alot of experience looking at electric motors so I could be looking at something that's out of place but I don't know it.
Any suggestions of what I could/should test next and pointers on how to do it?
Thanks!

Next update:
I had a friend (an ME) come over and give me a hand and we dropped the motor to inspect it. We couldn't find anything obviously wrong with it. Then we hooked the pos and neg cables back up to it without reinstalling the motor into the van and tried it like that. At first, the same thing would happen- spin at low throttle and then just stop. But after a while, it started running normally! The problem appeared to "fix itself". Now I've been working on cars long enough to know that the vast majority of problems don't just fix themselves and I was skeptical. I reinstalled the motor and sure enough, nothing had been "fixed", the van started to roll and then stopped, just like before.
So today I finally had some free time and wanted to test the POT
-what is the best way to test the POT?
-I also stuck a vmeter on the Pos and Neg cables at the motor and by hand moved the POT to see what voltage was going to motor, and the highest it ever got was around 11v. (I have a 120v pack).
-Why would it measure lots of V with the motor NOT hooked up and just a few with the motor hooked up?
Any thoughts?
TIA!

[jyanof]

Originally Posted by type2teach

-what is the best way to test the POT?
-I also stuck a vmeter on the Pos and Neg cables at the motor and by hand moved the POT to see what voltage was going to motor, and the highest it ever got was around 11v. (I have a 120v pack).
-Why would it measure lots of V with the motor NOT hooked up and just a few with the motor hooked up?
Any thoughts?
TIA!

I doubt it's the pot based on your previous charts. The output from the controller indicate that the pot is working well.

Would you repeat the test with another volt meter on the controller input from the battery? It should read the same as your battery voltage, but I'm almost betting that it'll be really low like the motor voltage.

[MPaulHolmes]

Please don't bid on these:
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haha. My retirement money came! Hurray! Solar videos and new DC controller soon to come. Well, pretty soon. The universal power source/motor controller will be called the Unitard.

[bennelson]

I'd be happy to try out the new universal power source/motor controller, but I'm not sure anyone here wants to see me in a Unitard.

[johnsiddle]

Originally Posted by MPaulHolmes

That's a beautiful heatsink!! I can't wait until you test it.

Duncan, I think some people may have gotten 600amp working, but I'm not sure about 700amp. There's sort of a limit to what you can do with a single mosfet driver like the mic4451. You might be able to use some gigamos mosfets with the same gate charge as the regular ones.

Paul, was there a particular reason you used one mosfet driver instead of ten (apart from cost).
I have copied your power board using ten drivers and ten 130A 200V Mosfets and just had a spectacular blow up.
Also when your current sensor trips does it cut the motor drive and return as soon as the current drops or is there a delay or something? I think mine created a strong juddering effect just before blowing up.