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Discussion Starter · #1 · (Edited)
Would it be possible to just have a bleeder system for each cell independent? (a single wire with a micro circuit board to control flow/read voltage) and what are the issues with that?

I thought it would provide the basic safety against a single cell overcharge when pack voltage is still lower and being charged. (maybe a buzzer for low voltage)

Also, what about transmitting data to each unit using the high voltage cables/bars as a transmission line? ex. http://en.wikipedia.org/wiki/Power-line_communication#Automotive_uses

And finally, has this already been done? hehe

Josh
(ps feel free to move this to "chit chat" if applicable.)
 

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Discussion Starter · #3 ·
Who told you that you needed a bms in the first place
My battery warranty requires bms logs (not that I care) but that's a starter reason. Also a BMS doesn't seem like a bad idea to me, I just don't like 60+ extra wires in my car when (in theory) maybe any desired realtime communication could all be done through the HV wire or bluetooth, etc.

look to advert on right "mini bms".
The miniBMS v2 wiring diagram shows an extra communications wire tying each cell to the next and the end cells to the brain (and then on to the controller) so it's a nice design, but perhaps there is still a way to have zero extra wires?

I suppose if one has contactors on both ends of the pack then you don't have a copper connection beyond the ends of the cells (mine only has a pack contactor on one end with an additional in the controller), but in this case perhaps a transmitter could be attached to one end of the pack to send data from the cell units?

Josh
 

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I did build a wireless system, but it still needs a central brain. So not quite what your looking for.
http://www.diyelectriccar.com/forum...ng-up-bms-monitoring-only-infrared-82772.html

The idea of using the HV cables is intriguing. I have 0 experience with powerline stuff. My guess is:
- Inject a x MHz carrier signal using a capacitor
- Use FSK, PSK or ASK for modulating the bits onto the carrier
- Use a common light weight error correction code like hamming code for correcting bit errors.
- Use a x MHz bandpass filter on the receiving side
- Decode
- Correct errors.
- Use a request/reply protocol (bidirectional communication) for bus arbitration.

I hope someone tries this :)
 
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