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Author Topic: 112 switches need reading  (Read 1820 times)
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Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law.
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As I said in my reply, it's when more than two switches are closed at once that you must have the diodes. Suppose switches A1 and B1 are closed. Then lines A and B are shorted together. So when you discover that driving A causes line 5 to be detected (as well as lines 1 and 2), you don't know whether it is A5 or B5 (or both) that is closed.
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Yes,  I am stupid today!! Adding the diodes is easy .
In case you wondered what this is all about.. here's the quick view.. I have 112 cells in a nom. 400 volt battery pack for my electric car that I am building. Need to know as a minimum if the pack is discharging  as when being driven if any cells are lower than the low limit . Also when charging except that I just have shunting across any cell that has reached full charge allowing the rest to get fully charged too. This is called a BMS, battery management system, and is the biggest PITN . There are chips that are meant to do this but the ones from MAXIM have shown a failure mode that makes their use questionable, ( EMAIL ME DIRECTLY IF INTERESTED IN THIS )  so I am designing a simple system with relays for isolation. Each cell will have it's own relay and the contacts are what is forming the 7 x 16 array. I can have number of these open or closed depending on the individual cell condition. so diodes it is.
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