I have been tinkering with BMS for some time now, and i found it very precise when not driving. When underway i find the EMI disturbing voltage reports. However it rarely happens that the system locks up. Probably watchdog is not even aware of the EMI. A friend of mine suggested the interference is normal for AC systems wheres for DC they dont happen. Well maybe the brushes throw something out...
So i decided to play with optical link. I will use IR LED from last out terminal and IR transistor on the receiving end. I designed modules that simply fasten on existing terminals on the cell boards. Of course the will require + connection to the battery to power the module, but it should be simple to put one more terminal to the Batt positive. Then 1mm plastic fibre will carry signal undisturbed to the master module which is protected inside Alu box. Also master powers outgoing module. Should work without major changes. I got the idea here:
http://www.rcgroups.com/forums/showthread.php?t=500234
Regarding 5W resistors, why not use 5W C5W car bulbs?
They are relatively cheap, a socket can be used to replace them if necessary and when you would want to perform regular inspection, your battery box will be all lit up
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Last time i used one 55W bulb to quickly bleed one cell to 2,8V. It took like 15minutes and it was with the others, requiring only a little bleeding in the end.
A