On Wed, May 7, 2014 at 11:06 PM, Jan Steinman via EV <ev@lists.evdl.org> wrote: >> From: Bill Dube <billd...@killacycle.com> >> >> The internal resistance of a battery does not change it's Ahr >> capacity. Not even a tiny amount. > > No, but it *does* determine how much of the battery capacity gets turned into > waste heat, no? > > Assuming voltage stays fairly constant, the power dissipated by internal > resistance rises with the square of the current drawn. That's energy that > isn't going into moving you forward. >
No. Don't confuse charge capacity with energy capacity. None of the charge capacity gets turned into heat, only some of the energy capacity gets turned into heat. That is why what Bill said is correct and why I monitor SOC (state of charge) of my batteries and not SOE (state of energy) to determine how much I have left in my battery. I know if I use it faster more energy is converted to heat. With LiFePO4 cells, however, the warmer they are the more energy efficient they become so it actually doesn't affect range as much as you might first think. Also, to assume voltage stays fairly constant with changing current is way off the mark of what happens. In fact, it is that very change in voltage at the terminals that accounts for the energy dissipated as heat internally in the cell since the current throughout the circuit is the same. -- 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)
