Paul & Sabrina's cheap DIY 144v motor controller

[flores]

Originally Posted by MPaulHolmes

It sure does make it easy to turn it into a charger. I guess that's one benefit! All you need then is an inductor and output capacitor, and badabing, badaboom, you have a charger.

Stupid question 1: doesn't it already have an output capacitor? The ring cap?
Stupid question 2: where does the inductor go? And why?

[MPaulHolmes]

The ring cap is the input capacitor. In a buck charger, instead of the motor, you have an inductor hooked to m+, and battery bank to be charged hooked to inductor's lead B. Output cap to inductor lead B as well. Output cap Neg to neg of Battery bank being charged. It makes an LC filter so the voltage and current are more stable.

Oh ya, you also need a rectifier before the ring cap if you are charging with AC.

[thingstodo]

Originally Posted by 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.

If you are using 3 sets of IGBTs, at 8 Khz, I think you may be able to alternate the switching - U+, V- ... V+, W- .... W+, U- ... at 24 khz (higher than I can hear) for a 'silent' mode? Dogs may not like it much, but I think I would

There would be 3X heat since you are switching 3X as often, so it would be *BAD* for heavy acceleration. But it may be good for cruising?

Just a random thought ...

[MPaulHolmes]

They were talking about something like you are describing on the EVTech list a bit ago. I bet that would work. My plan though is just to use spread spectrum switching. I got it working really well just yesterday. It sounds like the controller is telling someone to shoosh (for a really long time) in a library. I think it will blend in very nicely with the wind outside of the car.

[duncan]

The wind outside the car?

[MPaulHolmes]

Oh you know how theres sort of some background noise while driving, like the tires on the road, a little wind, etc. It would just blend in with that. My guess is that it wont be noticeable at all.

[thingstodo]

I listened to the spread spectrum 'white noise' that Paul posted.

Plus:
- does NOT sound like a Kelly DC controller, or a Curtis DC controller
- does NOT have the AC 'whine' at low speeds that industrial AC controllers typically have (2 Khz - 10 Khz carrier with ... apparently .. no randomize algorithmn). The typical AC 'whine' is most annoying IMHO below 20% speed.

Possible Minus:
- may be audible at low speeds ... but I've never heard car noises at low speed (without the ICE engine noises) so the car may be louder than I realize

HUGE PLUS:
- if it *REALLY* annoys me that much ... I can CHANGE IT!

[Astro]

Originally Posted by jedsmd

My two cents:

Keep it simple. Just run the 2gauge where it needs to go in the controller and lets us worry about hooking the other ends up. Each extra connection in the power path is an additional voltage drop and potential failure point.

How about just using cable glands to pass the cable through the end plates?
Some nicely insulated cable should allow the end plate to be made of metal if that makes it easier for Paul to fabricate. Would probably be more durable that way too.

So run the cable from the motor to the controller and right through the end plate and connect it internally to the bus. If we needed to remove the controller at some point then we could disconnect the cables at the motor end.
That should reduce the number of connection points. Also it would save Paul from having to supply any cables, we could just hook up the length of cable appropriate to our layout.

[MPaulHolmes]

OK, I need a plan for the wiring now. If I got orange 2gauge cable, then it would be "SAE" compliant I think. Here's my plan (so I can test each controller):
3 cables coming out of the controller will be around 3 feet long (from the point of connection inside the controller). They will be orange. All 3 must connect to the Motor Plus.

Here's the fuzzy part (but I'll sound assertive. Feel free to tell me to do something else):
3 cables will come out of the controller, and will all need to be connected to battery pack plus (maybe connect all 3 of them to a big fat 4/0 cable that runs to the battery pack plus). The lugs will protrude around 3-4 inches past the end cap, so I can use metal end caps with cable glands.

3 cables will come out of the controller , and will all need to be connected to battery pack NEGATIVE (maybe connect all 3 of them to a big fat 4/0 cable that runs to the battery pack NEGATIVE). The lugs will protrude around 3-4 inches past the end cap, so I can use metal end caps with cable glands.

You will need to connect Motor negative (a big fat 4/0 gauge cable) to battery pack negative (or to the 3 cables in the previous paragraph).

All of the cable coming out of the controller will be orange #2, terminated with #2 lugs with 5/16" holes.

I'm just running that up the flag pole, to see if anyone solutes it. If they do, then I'll find the necessary amounts needed, and beg and plead for the funds to buy it. haha.

[duncan]

Sounds super good to me