I don't think that math is right but you won't get 100% efficiency out a controller. I think Curtis advertises 88%. Current out of a battery is not calculated based on internal resistance. Internal resistance or Impedance of a battery can be modeled and measured but it doesn't act like a normal load. It's a chemical reaction and different chemistries will give you different currents. If it is not due to limits on the controller and the efficiency drop then I would say the batteries aren't at full capacity any more. The battery industry uses a 100-hour rate as an index to compare batteries of different types and sizes. The 100-hour rate is the amount of Ahs the battery will deliver during a 100-hour discharge. The capacity of a battery, in Ahs, is a dynamic number that is dependent on the discharge current.
For example, a battery that is discharged at 10A will give you more capacity than a battery that is discharged at 100A. With the 100-hr rate, the battery is able to deliver more Ahs than with the 20-hr rate because the 100-hr rate uses a much lower discharge current than the 20-hr rate. Both rates are used as baselines. Either rate, however, will give you the same view of a battery. A higher capacity battery will have higher 5 and 20 hour rates than a battery with lower capacity. They publish tables that you can look up to see these values. From: Lee Hart via EV <firstname.lastname@example.org> To: Electric Vehicle Discussion List <email@example.com> Cc: Lee Hart <leeah...@earthlink.net> Sent: Monday, September 11, 2017 11:40 PM Subject: Re: [EVDL] Slow due to 96V pack? From: lektwik via EV <firstname.lastname@example.org> >96V = Slug Not necessarily; but in this case, probably correct. 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. In practice, the resistance of the pack is a bit higher due to the wire and connectors. So a 200a max current is probably the most you can draw from the golf cart batteries before their voltage under load falls to 72v. Now, if you had a different kind of batteries with less internal resistance, or a controller that would cheerfully pull the battery voltage even lower, you'd have a lot more current, and peppier performance. For example, my old ComutaVan had a 72v pack of golf cart batteries, and a contactor controller. It would cheerfully pull 1000a from the batteries, and spin the tires if you "floored it" from a dead stop. I tried a Curtis 1221 400a controller; and it was *worse* than the contactor controller for accelleration, because it never came anywhere near 400a due to voltage sag. -- Excellence does not require perfection. -- Henry James -- Lee A. Hart http://www.sunrise-ev.com _______________________________________________ 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) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20170912/6fed2515/attachment.html> _______________________________________________ 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)