I have seen the same behavior with the LiFePO4 cells in my conversion. As the cells approach empty, the low voltage alert sounds under heavy acceleration. As they get closer to empty, it takes less current draw to cause the alert. There is very little capacity left at that point, and it's time to park the car and find a charge.
The motor and controller are trying to draw constant power, so when the voltage droops, current increases, which makes the voltage droop worse. Mike On February 25, 2016 8:08:26 AM MST, "Craig M. via EV" <[email protected]> wrote: > >I need some feedback for anyone who has seen the following effects. > >I want the maximum possible range out of my EV but when the battery is >weak (58 miles or so,) acceleration can be a problem. If I hold down >the accelerator pedal too long the voltage drops low. The motor pulls >a lot of current, and the motor may slow down as the battery rapidly >discharges. I have also observed that if the motor stalls, it draws >very high current and the battery is soon fully discharged. To get >home on a weak battery I have had to accelerate in steps or pulses. I >would lift my foot off the pedal for about a second and let the voltage >on the battery come back up before pressing the pedal down again to >accelerate. There is an alarm that sounds if the voltage on any cell >is too low or too high. I have an AC-50 motor and controller with the >regenerative feature and LIFEPO4 cells. This may be playing a role in >this effect. I would appreciate hearing from anyone who has pondered >the effects of voltage sag on batteries and motors. I have asked this >same que >stion elsewhere and I got back shrieks of how I am breaking the laws of >physics, motion or thermodynamics. I can't break those laws so I >frankly have stopped worrying about it. I am making observations and >trying to learn from them. >-------------- next part -------------- >An HTML attachment was scrubbed... >URL: ><http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20160225/af92877b/attachment.htm> >_______________________________________________ >UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub >http://lists.evdl.org/listinfo.cgi/ev-evdl.org >Read EVAngel's EV News at http://evdl.org/evln/ >Please discuss EV drag racing at NEDRA >(http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
