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Old 04-28-2009, 09:04 AM   #1064 (permalink)
MPaulHolmes's Avatar
Join Date: Feb 2008
Location: Maricopa, AZ (sort of. Actually outside of town)
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Michael's Electric Beetle - '71 Volkswagen Superbeetle 500000
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Here's a super condensed answer to questions:

Yes, I'm a substitute teacher, so my electronics skills are not very impressive. They don't teach you about resistors in substitute teacher school, only how to kick naughty kids out of class. Everything I learned I picked up by asking questions on the EVTech list since December.

The nice thing is there are power electronics experts that are helping with the control section for free now, so it will be much more robust once it's done.

I think we are going to make a wiki on here. It will have the updated information.

The mosfet failure is pretty well understood, and the same problem can't happen now.

They have body diodes.

High voltage mosfets have a much higher RdsON then what I'm using. Find me a 1000v mosfet with an RdsON of 8 mOhms for 4 dollars, and I'll switch immediately.

DC series wound forklift motors are cheap and abundant. My goal is to make a freeway capable electric car cost $1200-1500 less than it would otherwise be by making the controller inexpensive.

It's switching at 15.5 KHz, but IGBTs are not a good idea below around 275-300 volts. They have a fixed voltage drop, which makes for greater heat loss below that range. Also, it's cheaper to use 10 $4 mosfets rather than 2 or 3 igbt modules that are several hundred dollars each new. A 1200v 600 amp IGBT module looks impressive, but it can't be run anywhere near it max ratings. They must be paralleled, which isn't the simplest thing to do in the world.

Most commercial EVs? You mean the $109,000 Tesla? The $20,000 25 mph Zenn? I'm talking about a home built $2000-4000 70 mph electric car with a 30-40 mile range. There are still basically no commercial EVs (sort of).

Good point about the u-controller being able to hang. I'm going to make use of the watchdog timer to help with that potential issue.

A PB-6 pot is the standard. You could go some sort of electronics route. I think the Zilla uses some sort of hall effect throttle, or at least has something as an option.

Don't worry, wiki coming soon.
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