John, first of all, a '65 Falcon conversion is a SUPER COOL idea. I'm jealous. Well done!
Second, I'm far from a lithium battery expert, but I'm having trouble seeing why you're concerned with "bottom balancing." I don't see why it would be necessary or even desirable. As I understand it, the BMS's job is to (1) Limit and eventually shut down the discharge when any cell is flat (2) Limit the charge rate when any cell is full (3) Balance - that is bring up the other cells to full charge without overcharging the already-full cells This is how you get the optimum capacity from your battery without damaging it. It seems to me that if the BMS can't bring all the cells up to full charge even with a very long balancing session, then one short term solution is to individually charge each cell until it's full. Then see if the BMS can keep the cells properly balanced over a period of cycling. If it can't, it seems likely that the cells are inconsistent in usable capacity. This can be from several causes including (1) Cells aging at different rates (2) Some cells newer than others (replaced for premature failure?) (3) Careless manufacturing quality control which causes inconsistent capacity and/or varying self-discharge levels (4) Inconsistent temperature across cells in the battery, which can easlly happen in coversions where the cells are distributed around the car with multiple boxes and simple/passive air cooling (5) Tapping the battery for various loads at different voltages As I say I'm not an expert and those here who are can probably add to this list. I hope that I haven't given you any incorrect information, and welcome corrections if I have. David Roden, EVDL moderator & general lackey To reach me, don't reply to this message; I won't get it. Use my offlist address here : http://evdl.org/help/index.html#supt = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = I found one day in school a boy of medium size ill-treating a smaller boy. I expostulated, but he replied: "The bigs hit me, so I hit the babies; that's fair." In these words he epitomized the history of the human race. -- Bertrand Russell, "Education and the Social Order" = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/ LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org
