One system I saw awhile back...Originally Posted by steiner
A guy had a similar deal going with a bunch of LiPo batt's in an EV.
He had a bunch of 'modules' made, one for each LiPo cell, mounted right on top of the terminals.
The modules were all identical. Each had a few MOSFETs (one for basically shorting across the cell terminals, and a couple more for 'disconnecting' the cell from the string, a precision Vref, and a 12F683 (I think).
The basic operation was...the PIC would draw uA off the cell itself for running, low power mode, slow clock, sleeping most of the time, etc.etc.etc...
The 'shorting' MOSFET was 'off' most of the time, the 'disconnect' MOSFETs were 'on' most of the time. (I'm not 100% sure on the MOSFET idea, this was awhile back, but this is how I remember it)
The PIC on top of each cell would wake up once in awhile, check the cells voltage against the precision Vref on the module. If the cell's voltage was too low, it would 'open' the 'disconnect' MOSFETs, and turn on the 'shorting' MOSFET, keeping that cell from draining too low by bypassing it. If the cells voltage got too close to the upper cutoff, same thing happened, bypass it to keep the charge off of it.
There was also a serial line coming in and going out to a 'MASTER' PIC which monitored all of the PICs on the cells and these serial lines were set up in a daisy chain. PIC-Cell#1 would generate a message containing voltage and send it to PIC-Cell#2. PIC-Cell#2 would get that message, add it's own info and send it to PIC-Cell#3 and so on and so on. The MASTER PIC would get all this info and display it as needed.
I would almost think that this method, with 24 identical modules, all running the same code, doing the same function, would almost be easier than trying to tie a bunch of analog inputs/outputs/multiplexers together.
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