Paul & Sabrina's cheap DIY 144v motor controller

[flores]

I'll set mine to 16000

[MPaulHolmes]

Hmm... How about "time to zero current" from max throttle? It's fun not pile-driving into a car in front of you. haha. Maybe instantaneous would be best?

[jedsmd]

Originally Posted by MPaulHolmes

Hmm... How about "time to zero current" from max throttle? It's fun not pile-driving into a car in front of you. haha. Maybe instantaneous would be best?

Instantaneous - ramp down should be controlled by how fast you can lift your foot.

[MPaulHolmes]

I hate to nickel and dime you beta testers, but here goes:
You guys will need 3 pieces of at least 3 foot, 2 gauge cable. Each pieces goes with its very own IGBT/current sensor to the motor. They need to be 3 feet long each, since 2 gauge cable has a voltage drop of about 0.2v at 400amp through 3 feet of cable. That will help with current sharing of the IGBTs. If one IGBT attempts to be a current hog, his cable will say "Oh no you di'ent!", and have a larger voltage drop, causing less current to go through that IGBT, bringing that naughty child back in line with his other 2 brothers.

So, that's 9 feet of 2 gauge cable per person. Now is a mounting question. Do you guys want to just bolt the 3 cables right to the motor? Or bolt them to a big fat 0000 cable (which is about the same cross sectional area as 3 2gauge cables), which gets bolted to the motor? I don't know how close your motor is to the controller.

I should probably get the 2 gauge cable, so I can mount a current sensor to each one, but that step isn't rocket science and you could do it too. But I would like to test each controller before mailing it out!

All this to say, I need 2 gauge cable! and I have no more money left. LOL.

3 kits * 9 feet each is... (pulls out calculator)... 27 feet!

And... to add insult to injury...

Now, for connecting B+ and B-. How about 2 pieces of 1 foot, 2gauge cable for B+, and 2 pieces for B-. I need to spread the current across the capacitor, I think, since there are so many tabs. I don't want to have a single connection point, since the tabs aren't super thick. That makes for 4 more feet of 2 gauge cable per person. So, 13 feet per person... And 4 more lugs per person... The battery current is sure to be smaller than the motor current, so I was thinking 2 cables of 2 gauge is probably OK. Does anyone have batteries that can sustain over 1000 amps?

So, I need 30 lugs, and 40 feet of 2gauge cable.

(if you want to get your own cable, or can find 40 feet, let me know)
Welding Cable 2 AWG 50

ONE ORDER OF THESE: (it makes for an extra 10 left over. If you can find 30 lugs for sale, let me know)
20 2 Gauge 2 AWG x 5 16 in Tinned Copper Lug Battery Cable Connector Terminal | eBay

And then ONE ORDER OF SMALLER HOLE LUGS. Because those capacitor screws are pretty small.

The last part is the end caps. I haven't gotten that yet either. I was thinking 1/4" or thicker of some plasticky sort of material. I hate this part of controller making. The dang enclosure, and interface to the outside world.

P.S.: INSTANTANEOUS TURNOFF IT IS!

EDIT: Or maybe several 2 gauge cables go to a single lug output that's super big and fat. I don't have a way to crimp 0000 lugs though.

[MPaulHolmes]

I wanted to do the forced current sharing way because people who will be doing this will likely just buy 3 IGBTs from Ebay, which will not likely be well matched.

4 6gauge cables might be better for B+ and B- (4 each). It's easier to find small lugs with small holes than big lugs with small holes.

[criley]

Greetings,

I have been reading this thread from the beginning, and I have a couple of questions:
In several early posts, it's mentioned that the controller board and the power section do not share a ground. Is there a reason for that other than the controller is powered by a separate battery?

I ask because I'm considering building one of these for my "golf cart" which has limited space for batteries. I was considering a voltage reducer to pull power from the main pack. Although maybe a small 12v battery would be better (is there such a thing?)
I emphasize "golf cart" because I've never used it for golf.

Secondly, in the early posts I have read about "advancing the motor brushes". Can someone kindly explain what that is to me (or point me to something good that I can read?)

Finally, there's mention of a PI loop. I googled pi motor control and get lots of results about raspberry pi, which made me hungry but are probably not what I'm looking for. What are alternatives to pi? (aside from cornbread, which is usually square, but my wife's is round.). Any suggested reading?

Thanks!

Believe it or not I'm really enjoying my read through the thread. I have at least 400 pages of posts to go. I read on my tablet before bed, so this might take a while. Not that I'm implying that you guys put me to sleep or anything. Even though I guess technically you do.

[flores]

Originally Posted by criley

Greetings,

In several early posts, it's mentioned that the controller board and the power section do not share a ground. Is there a reason for that other than the controller is powered by a separate battery?

This is because you NEVER want to connect the high voltage pack ground to the chassis of the car.. it's dangerous.
Because the 12V supply is likely to be connected to ground these two are not connected in the controller.

[MPaulHolmes]

The power ground on a motor controller can be out of control and crazy. Evidently this can cause problems with the microcontroller if it has the same ground. One thing you could do is get a small dc-dc converter that takes the pack voltage and turns it into isolated 12v for the control power. Just a few watts would be enough.

As far as motor brushes go, I have no idea how to do that. haha. There are people on here who have done it. It's to optimize a motor for higher voltages. It cuts down on arcing. I think you rotate the brushes some unknown number of degrees, and then reattach them somehow.

PI control (without the D):
PID controller - Wikipedia, the free encyclopedia

I'm warning you. Pretty soon you will hit a naked picture of Kim Jung Il. I can't remember what page it's on, but I posted it, so I know for sure it's on here. haha.

[jedsmd]

Originally Posted by MPaulHolmes

I hate to nickel and dime you beta testers, but here goes: ....
You guys will need 3 pieces of at least 3 foot, 2 gauge cable. Each pieces goes with its very own IGBT/current sensor to the motor. They need to be 3 feet long each...

Three feet of cable is a little long but I will make that work.

Are you regulating the positive or negative side, that is does the other end of the motor returns to batt+ or batt- ?

I should probably get the 2 gauge cable, so I can mount a current sensor to each one, but that step isn't rocket science and you could do it too. But I would like to test each controller before mailing it out!

I see no advantage to us installing the current sensors, you might as well install them.

Now, for connecting B+ and B-. How about 2 pieces of 1 foot, 2gauge cable for B+, and 2 pieces for B-.

On mine I would like 12" on B+ and 20" on B-

I have no more money left. LOL.

Are you hinting that it is time for a progress payment?

[MPaulHolmes]

You know, we could shoot for a 0.2v drop at 500amp instead of 400amp. That would shorten the 3 foot cable to... drum roll please... 2.5 feet (starting from the igbts inside the controller, so that eats up 6-8 inches right there I think). Any length will just help keep things balanced. There's no rule that says it has to be a particular length though. If you find that the IGBTs always have the same current, then you could shorten the cables.


It's a high side controller, so you will have the following wiring (ignoring all safety stuff):

BATTERY PACK + -------------- CONTROLLER +
Battery Pack negative --------------- controller negative
Motor Negative ----------- controller negative (or battery pack negative)
Controller M+ ------------------ Motor M+

On mine I would like 12" on B+ and 20" on B-

That's not not, I repeat, not a problem! I"m thinking a couple 0000 lugs sticking out of the end cap for attaching to B+ and B-. Then, how I connect it all inside to the capacitor is pretty irrelevant to the outside world. I need me a 0000 lug crimper. Actually, I may be able to make one with some big cable cutters I have and an angle grinder. I already turned it into a 2 gauge crimper, now I just need to grind the hole a little bigger. Or a small piece of bus bar might be good. Oh the possibilities are endless.