Paul & Sabrina's cheap DIY 144v motor controller

[isaac_alaska]

thanks paul! i learn just a little bit more every day

back to the capacitor topic, i was thinking about it again, and the rms current rating on the capacitor is just the ripple current. and i haven't actually tested this on something this big yet, but it seems that the capacitor just kind of has to fill in the corners of the pulse, to make it a nice square pulse, and the batteries are still doing most of the actual current. i'm not sure how it relates in terms of percentages, but i would bet that the ripple current on the capacitor is probably less than 20% or so of motor current. just how i'm picturing it in my head...

*EDIT*
to put this capacitor in perspective, we can compare it with the existing capacitor bank in the cougar 1k. 22 electrolytics in parallel:
2.84 amps ripple current each
149 mOhm ESR each
in parallel with ten poly caps,
7.5 mOhm ESR each=.75 mOhm total
this gives
62.48 amps ripple for the whole stack
~.74 mOhm total ESR

compare this with the ring cap:
500 amps ripple
.125 mOhm ESR

new capacitor should be more than up to the job

[Nevyn]

HOT DAWG! Not only does that simplify the build, but I bet it also reduces cost, too! I'm getting more excited to work on/finish this!

On that note, I got the Jetta in my garage. I need to de-burr my heatsinks, program the controller, get bus bars, and then should be able to test it out! Oh, have to build a programmer, too.

[MPaulHolmes]

Well, maybe not SAVE money, but it's definitely the best and the simplest. You probably only need a couple film caps if any (no other brand uses them, like Curtis), and the electrolytics are $2 each, so it's probably around $45 for the caps compared to $198, but these are definitely apples and oranges.

[Nevyn]

Oh. Well, doing this on a shoestring budget, we may go the multi-cap way, then. Thanks for the info!

[MPaulHolmes]

Hey Louman! That was just a test board, and I don't have any more. It also had some minor design flaws, but I'm starting to think that the real problem may have been the lack of shielding on the current sensor. The LEM is designed to tolerate a noisy environment, but Freyguy found an interesting application note that shows you need a little mu-metal shield around the base of the bus bar, covering the sensor or you can get significant errors.

[harlequin2]

Originally Posted by LouMan

Well crapola, LOL thanks Paul, I bet it's something so simple that just looking at it isn't going to find it, like a trace in the wrong place or a wrong value on some part that at first hand should be the right part
I hope we can get some of them off the press soon, I see yaw took some of my advice about the labeling the connectors in there on section

Hey LouMan, good to see you back in action and it looks like you have some money again! (Hint, hint)

[isaac_alaska]

Originally Posted by MPaulHolmes

Hey Louman! That was just a test board, and I don't have any more. It also had some minor design flaws, but I'm starting to think that the real problem may have been the lack of shielding on the current sensor. The LEM is designed to tolerate a noisy environment, but Freyguy found an interesting application note that shows you need a little mu-metal shield around the base of the bus bar, covering the sensor or you can get significant errors.

ah! this explains why there isn't much documentation on this one. well hopefully i'll get it running and get some real world tests for it!

[XmodAlloy]

Hey everybody!
Man, this stuff is getting mighty exciting! 1000 Amps of home-brew power, I'm diggin' it Paul!
Anyway, I had a minor concerning incident today, I was revving the massive motor in my Geo a bit and decided to see what kind of RPM I could get out of it with 8 drive batteries, all went well and nothing is blown up yet, but when it got to a certain fairly high RPM the volt meter began to flutter badly into the 150 volt range with only 96 volts of nominal power. the meter is analog so it's nt some bug that a digital one might have with high frequency input. I suspect it's the back EMF from the motor surpassing 200 volts and jumping the on-board diodes of the MOSFETs, does that sound at least possible? I already have replaced the main blocking diodes with 600 volt ones after the 200 volt ones decided to become silicon popcorn.
Obviously I should restrain myself from revving the motor that high again but I am now very curious about what can be causing this voltage spiking back into my batteries.
The motor in my car is a mysterious 12 inch monstrosity which refuses to pull more than 250 amps and is quite happy to spew back all the voltage I can get rid of when running.
It's overkill I know, but I was rather naive when I bought it and everything else is built around it now, otherwise I would swap it out for something a little smaller. Who would have guessed there is such a thing as too big? Lol...
-Donovan Gibson.
P.S. I really don't mean to bug you any more Paul, it's just I can't help it! I'm cursed with oddities in my car's system!

[Green Eggs and Sam]

Hello Everyone,

I am a reporter for The Calgary Journal, and I am researching a story on hypermiling. I am looking for someone in the Calgary area to talk to about how they hypermile, the benefits they have seen and the mods on their vehicle. Please send me a PM and we can set something up.

Thanks in advance!

[mrbigh]

Getting back on the board after some time...............