That made no sense to me but a DC motor controller takes the input voltage to power mosfets or igbts which switch the power on and off with a pwm signal to get the desired output to drive a motor. It has no knowledge of the battery impedance.
Sent from my iPhone > On Sep 13, 2017, at 6:09 PM, Roger Stockton via EV <ev@lists.evdl.org> wrote: > > paul dove wrote: > >> You said:Here's my guess: A 6v golf cart battery has an internal >> resistance of about 5 milliohms (0.005 ohms). A 96v pack has 16 of them; >> so the resistance is 0.005 x 16 = 0.08 ohms. Let's say the Zilla limits >> voltage to 72v (i.e. it won't pull the pack below 72v). Then the most >> current you can get is I = V/R = (96v-72v) / 0.08 ohms) = 300 amps. >> **It is either going to be 96v/0.08, 72v/0.08, or somewhere in between. >> The voltage won't be 24/0.08 at any time.So, somewhere between 1200 and >> 900 amps. > > You are (almost) correct only if you *short* the battery terminals, so that > the voltage on the load side of the internal resistance is 0V. > > This is *not* the case with a controller that enforces a low voltage cutoff, > such as the 72V value in the example: > > > 0.08 ohm > Internal R > +-------/\/\/\/\------oo------+ > | | > --+-- ideal / 72V > --- 96V \ minimum load > ----- battery / voltage > -+- \ > | | > +---------------------oo------+ > > The controller effectively regulates the voltage on the load side of the > battery internal resistance such that the voltage difference across the > internal resistance will indeed be approximately as Lee states. And the > maximum battery current that *this* load can draw will be on the order of > (96-72)/0.08=300A. > > Cheers, > > Roger. > > > > _______________________________________________ > 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)
