Quote:
Originally Posted by MetroMPG
PS if you want to save money, you don't necessarily have to buy a shunt. AFTER I bought our shunt & ammeter (600A, which it turns out is too high a rating for our needs), I read you can make your own. It's just a calibrated conductor, with a known voltage drop across its length.
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I spent a good amount of time searching for information on making my own shunt. I ended up buying a 1200A 50mV shunt, which I am sure is WAY too high, but you never know with Ni-Cad batteries. I'd rather build things to too high a capacity than start burning stuff up. I'll be using a home-made serial interface 6-channel multimeter plugged into a spare laptop and running custom Visual Basic software for my gauges, so I'll be able to calibrate it to whatever the full-scale reading actually ends up being. I do only have 1.2mV resolution on the meter though. If I end up running 40amps or so for most around-town driving, I'll be reading only 1.6mV, which will be pretty much the bottom of my scale. For acceleration though, it should be a bit better.
Perhaps I can use the shunt I bought to calibrate some other conductor. Then again, one of the guys at work says he's got an old airplane shunt or two for me if I want them. I'm guessing they're around 200-500A.
My project is going over-budget very quickly with "R&D" spending, but I won't be including that in the cost 'to build the car'. When I get everything dialed in and know it works, I'll put it up open-source style for the rest of us wanting to make an electric car for a reasonable amount of money (sub $2000, including car, not including batteries).
Hybrid Mode
