Paul & Sabrina's cheap DIY 144v motor controller

[MPaulHolmes]

Ben, the heatsink is.... HERE!!! YAHOO! It is way more heavy duty and fancy than I expected! It is going to work really really well! I'm so grateful, Ben! When you test it out, I think you'll be able to be that much more lead footed. Speaking of heatsinks:

I found that attaching the mosfets/diodes directly to the heat spreader, and then insulating the heat spreader from the heat sink is NOT how it should be done. I tried it, and I think the giant heat spreader acted like a big sponge. It seemed to soak up each pulse, allowing only a very small pulse to make it to the motor. It wouldn't even turn the wheel at 12v. So, the heat spreader will be bolted with actual metal bolts directly to Ben's heat sink, and the insulating sheet from Rod Hower will insulate the mosfets/diodes from the heat spreader.

The capacitor side of the pcb in ExpressSCH is finished. Accurate to +/- 0.5 mm.

[MPaulHolmes]

There were some 3/8" brass (copper alloy!) machine screws on ebay for $0.20 each (and that includes the cost of shipping)! They are used to electrically connect the capacitors to B+ and B-. It's sort of hard to explain. You would need to see a schematic. All 500 amps (or whatever) needs to go through those bolts to complete the circuit.

I got enough for 10 or 11 controllers (116)! And they were new too. Without the cost of shipping, from boltdepot.com, they are $1.63 each! The cost of an open source motor controller just dropped by $15.73.

[esoneson]

Paul and Sabrina,
I want to take a moment to thank you for all your hard work on this open source project. I am a software engineer (RTOS) but know next to nothing about EE. I also am looking forward to attempting to be one of your first clients for your open source controller projects. Others out there know that there is a market for good reliable hearty controllers but they are not going the open source path. Shame on them. You are the shining example of helping others with your talents and time. It is much appreciated!!

I was the one who asked you to name the Mosfets I adopted after my dogs Emma and Jake. Now, just to make sure that you are very careful with all those Mosfets I thought I would give them a little personality to make sure that you treat them carefully. Attached are pictures of Emma and Jake.

Good luck with the project. There are many more people out here who are also very thankful that you are doing such a good job with this project. It will only do good for both home-brew EVers and the EV industry as a whole.

Many Thanks.

Eric

[MPaulHolmes]

Your encouraging words me a lot to us, Eric! And your dogs are adorable, too! My wife loved the boarder on the second picture. (She does lots of video and picture editing) Our baby loves dogs, but we don't have one yet. I think we should get a big one like your labs. He would love that. Your mos-doggies will be used to help people drive down the road without letting out poisonous fumes! Then your real dogs won't have to choke on stinky air every time they go outside.

I'm doing up a word document that has all the coordinates in millimeters (upper left is 0,0 because of all my dang video game programming, it's a habit) for drill points of the PCB, their diameter, and etching paths. Also, the picture will be saved as a JPG scaled correctly. So, if you choose to print it, you can then lay the ink onto the PCB, and then etch/drill it that way, or you can convert the document with the coordinates to a file that a CNC can read, and it will do everything for you.

It's just the first draft PCB layout. I think it will be good, though.

[MPaulHolmes]

OK, so I've got good news, and I've got some freakin awesome news!

Good news: Open Source contoller price just dropped by 150 - 56 = $94. Let me say that again: Take $94 off that controller price! The EVTech group just brought to my attention a new mosfet that is 200v, about 2 times as efficient as the other 200v mosfets that I was about to order, and if you buy them in bulk, they are $5.68 each! The other 200v mosfets were about $15 in bulk.

Other good news: It may be possible to increase the current limit rather significantly with the same number of components with some tricky coding! Ian brought this to the EVTech group's attention. It is really cool! More info on this soon! Like maybe 144v 1000amp under certain circumstances, and 144v 500amp safely!

[Daveedo]

Wow! That's a significant savings. Keep up the good work on this project!

[Daox]

Wow, great news! Keep up the great work Paul.

[bennelson]

Originally Posted by MPaulHolmes

Like maybe 144v 1000amp under certain circumstances, and 144v 500amp safely!

A world of 1000 Amp Geo Metros and Super-Beetles? Dare I dream it!!?!?

Now we are going to need cheap batteries that can give that sort of power.

No, wait, home-built Super-Caps!!

Leyden jar of DOOM!

[MPaulHolmes]

Each mosfet/diode can handle 50 amps for a while (maybe 1 minute?) until things heat up too much. But read the datasheet. The mosfet is no problem. It can handle 130 amps continuous (well, it would need some AMAZING heat sinking, thanks ben, and the leads might not like that much).

The diode is rated for Irms = 50 amps, but it's root mean square! So, to be safe, all you have to do is keep both diode and mosfet root mean square current under 50 amps. This allows for higher peak currents in the current limiting software under most circumstances.

So, assuming that you limit Irms to 50 amps for both the mosfets and diodes,

Here's a table of controller current limit:

0% PWM DUTY-- 500 amp current limit
10% PWM DUTY-- 527 amp current limit
20% PWM DUTY-- 559 amp current limit
30% PWM DUTY-- 598 amp current limit
40% PWM DUTY-- 645 amp current limit
50% PWM DUTY-- 707 amp current limit
60% PWM DUTY-- 645 amp current limit
70% PWM DUTY-- 598 amp current limit
80% PWM DUTY-- 559 amp current limit
90% PWM DUTY-- 527 amp current limit
100% PWM DUTY-- 500 amp current limit

[bennelson]

I SOOOO want dibs on road testing this thing.

Seriously, I am going to load up 6 more batteries in the Metro right now to see how it handles - er, if it handles...

I need to get upgraded suspension and charging done before you finish the controller!