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)