> Anyone have a solution to this quandary other than a full bms? Half pack voltage monitor. Lee Hart proposed this years ago and a slight modification and installing a volt meter that reads double the input voltage will give the half pack voltage difference. The chance of cells in each half of the pack doing the same thing on average is quite slim so that rogue cell would be found rather quickly. In your example, the low capacity cell would show up as a high voltage cell at the end of charge so relatively quick to find in a pack, even if the pack had 100 cells in it. You would only have to make 50 readings because the monitor tells you which half to check out. My blog shows how I made mine.
On Tue, Apr 22, 2014 at 9:08 AM, Marcus Reddish <[email protected]> wrote: > If the cells are bottom balanced at a voltage lower than the low-voltage > cutoff of the charger, then the low end is taken care of. A "deep" cycle > will not bother them. For example, if you have 100 cells then bottom > balance at 2.6V and low-voltage cut-off at 275V. > > But what about the high end? How do you know if one of the cells is almost > full even though you cut the charge off early? What if that cell is losing > capacity and each charge cycle it gets closer to the danger zone? What if > one night it goes over the line and gets damaged, losing even more > capacity? I can see that it is easy to find the weakest cell and monitor > that one (or several) cell. Fairly easy to terminate charging if that cell > goes too high. However, doesn't the "monitoring" of a cell use energy and > be the cause of drift? How to watch that weakest cell without affecting > it? Perhaps once a year watch it during the end of the charge cycle? > Anyone have a solution to this quandary other than a full bms? > > -- David D. Nelson http://evalbum.com/1328 http://www.levforum.com _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
