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Old 06-16-2009, 09:48 AM   #1721 (permalink)
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Quote:
Originally Posted by charlie_fd View Post
The code you are using for serial link (chris stuff) is converting from hex to ASCII inside the uC witch in my opinion is a waste of uC cycles (the conversion can be done in the client on the computer). Also, you are using the classic "wait for transmission ready" algorithm so every second you will stop the program to do the ASCII conversion (3 characters) and the transmission of 5 characters. Have you taken a look at the interrupt based transmission algorithm I'm using?
Well, the code I used (threw together is more like it) was as simple as possible so that I wouldn't have to re-mail the engineer chips for testing.
I plan on using interrupts for the input and outputs, definitely! I had no way of testing anything in a reasonable amount of time, so I went for super simple.

by! I need to leave! Must go to work!

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Old 06-16-2009, 09:56 AM   #1722 (permalink)
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Originally Posted by wjdennis View Post
Guys, I'm not trying to be persnickety or contrary here. I asked a question that was on-topic, about the controller and its possible use as a charger. My follow-up questions were going to be able how to size the inductor so that when I built the controller I could test it as a charger, too. But I got responses about choosing the right battery pack and energy losses and pack swapping. I've already got my battery pack. My EV goes over 100 miles on a charge. I drive it 88 miles round-trip to work. It just has trouble with sagging on steep hills, and Lee Hart recommended the solution I mentioned, getting a small second pack that could handle the high-demand draws for hills, and have my existing pack supply a constant 70A. Paul's controller seems like a good solution since I'm planning on building one anyway.

Bill
wjdennis, your EV goes 100 miles on a charge??!! If Lee Hart suggested it, then it will almost certainly work. I'm sorry for making light of it with the comment about the hydrogen. I was just being goofy. I'm not sure about correct inductor sizing. hmm... That's a great question. The inductance in an EV motor is around 50-100 uH or something of that order of magnitude.
I need to go back and read what Lee described.

EDIT: OK, I read it! Yes, I think it would work. Maybe use a larger inductance than a motor's for smoother charging of batteries? Or maybe that doesn't matter? Those dang Lithium batteries are like 99% efficient with their charging. I can't wait to hear how something like that would turn out.
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Old 06-16-2009, 10:23 AM   #1723 (permalink)
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Originally Posted by MPaulHolmes View Post
Those dang Lithium batteries are like 99% efficient with their charging.
No, not with a simple constant current applied to them. and that is precisely why this discussion about charging batteries belongs in another thread (hint, hint)
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Old 06-16-2009, 10:31 AM   #1724 (permalink)
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Quote:
Originally Posted by MPaulHolmes View Post
wjdennis, your EV goes 100 miles on a charge??!!
Thanks, Paul. Yes, the car has 36Kwh of Lithium-Cobalt cells on board (300Ah). Using 238 Wh/mile at 65 mph, the car's range is really closer to 150 miles at 100% DOD (though I'd for sure never try it!). Here's a one-minute video of my first test drive last year. It also shows how mountainous the terrain is here:


The issue with these LCP cells (LFP wasn't yet available when I bought my pack) is that they're rated for only .3C continuous. At 100A at 65 mph on flat roads, that works out pretty well. But I soon found out that the freeways here aren't flat--they go up and down all the time which I never noticed in my ICE vehicle. So the cells sag badly and overheat.

I'm really excited about trying your controller to pull 70A-90A continuous from the LCP cells.

Bill
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Old 06-16-2009, 10:40 AM   #1725 (permalink)
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Bill, if you only need 70-90 amps continuous, you can conservatively get away with maybe 4 or 5 mosfet/diode pairs and much fewer capacitors, since each mosfet/diode pair can handle 50 amps. A mini controller. Man, you weren't joking about those mountains.
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Old 06-16-2009, 02:12 PM   #1726 (permalink)
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Sorry for complaining then.

I thought you were planning this, not applying a "fix".

As fixes go it seems OK, your car already does what you want, bar a little problem, so fix that problem.

@Paul:

Which components see the increased current from free-wheeling? Would he even need those for charging duty?

(or am I thinking of an AC motor?)
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Old 06-16-2009, 03:42 PM   #1727 (permalink)
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Well, the freewheel diodes are needed for when the mosfets switch off 16000 times per second. Otherwise it would be like a piledriver of current destroying all the mosfets (because of the inductance).

OH HECK YA: I have just been informed that there is something from Digikey at the door. LIke almost $400 worth of yellermonkeypoo from Digikey! by!
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Old 06-16-2009, 09:00 PM   #1728 (permalink)
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New to this site. Just wanted to see how it works.
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Old 06-16-2009, 09:38 PM   #1729 (permalink)
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Hey Royal! New to the site, but not new to supporting the project! Thank you again, Royal! Welcome!
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Old 06-16-2009, 09:38 PM   #1730 (permalink)
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One more check.

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