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Old 03-20-2017, 02:16 AM   #3061 (permalink)
MPaulHolmes
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Join Date: Feb 2008
Location: Maricopa, AZ (sort of. Actually outside of town)
Posts: 3,753

Michael's Electric Beetle - '71 Volkswagen Superbeetle 500000
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Harold, I'd love to learn more about that motor. Post away (here or in a new thread).

thingstodo, I never posted anything much about the BMS. A microcontroller powered by the 12v system supply monitoring 'n' battery voltages. It monitors the 'n' batteries by receiving the voltages from little attiny25 microcontrollers that are powered by each cell. They send the voltage by a sort of morse code across optocouplers. The attinys are only powered when their cell circuit is enabled, so if the 12v power is off, there's zero draw from the cells. One neat trick was, for each attiny25 to measure its cell's voltage, it would just measure a 1.25v reference on the A/D channel. Then, from that you can infer the cell's voltage. For example, if you read 1023, that would mean the cell's voltage was 1.25v. But if you read 512, that would mean the cell's voltage was 2.5v, etc...

We fly out tomorrow! yay. haha My brother in law is getting married.

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