Thread: Low cost BMS
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Old 07-07-2011, 05:31 PM   #7 (permalink)
harlequin2
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The micro has an operating voltage of 1.8 to 5.5 and yes, it is powered by the cell that it is connected to. Because I wish to use a single byte to carry the cell voltage information, I have limited the voltage range that can be measured to 2.2 to 4.0 which more than covers the needs of Li cells.

Using a single byte cuts down the comms overhead.

It is a "daisy chain" system where each module is connected to the next passes its data from on through the chain until finally ending up back at the master.

The parts are labelled on the circuit diagram.

The shunts are indeed connected across each cell with a transistor sitch to turn them on or off. Yes, this wastes energy but any other cell balancing system is immensely more complex and expensive. The shunt resistor system is adequate provided you never let your cells get very far out of balance.

Hope this helps!
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