Ben, It is not the motor asking for a certain amount of electricity, the setup: battery - controller - motor places the motor in the dependent position, how much that the *controller* allows to flow from the battery. So, the short of it is that if the battery cannot deliver as much as the motor could be taking, then it is the task of the controller that limits the current (or voltage) to the motor. This means - *you* need to program the controller to limit the output to the motor to a safe level for both motor and batteries. NOTE that if the batteries are capable of delivering more power than the
motor can handle, again it is the controller that regulates a safe amount to be delivered, though the controller can be setup to deliver an instantaneous large amount and throttle back to avoid overheating or otherwise damaging the motor. Direct Drive tends to "lug" the motor, meaning: low RPM and high torque. Torque is produced from current through the motor. NOTE that for high motor current, it is not required that the batteries are capable of the same current, as the controller can "multiply" current at lower output voltage, so the controller and motor must be capable of handling high current for a direct drive setup, or else you will be very disappointed by the result. For example, if the motor is capable of "only" carrying a peak 1000A while the voltage on the motor is always below 30V because it is running at such low RPM, then there is no way to force the motor to deliver more than 30kW even though your battery pack may be 144V and 200kW! Note that if you can put a 2:1 gearing between motor and shaft, your current goes down 2x and voltage goes up 2x so that means 500A 60V, much more reasonable! If your motor allows a peak of 2000A and at the normal driving speeds can take aound 50V then you are already in the 100kW range, but now there are very few controllers that can dish out 2000A, in fact I only know one affordable version and it is the Zilla 2K which is a DC controller. For direct drive it will likely need a pretty beefy DC motor, especially the brush setup needs to survive the 2000A currents, but drag racers have shown that it can be done. Forced cooling of the motor and brushes is a must! My previous EV was a US Electricar truck that was a factory converted S10. It retained the manual gearbox but there was no stick - the box was permanently locked in 2nd gear as a fixed reduction, so that the entire setup allowed the AC motor to spin faster, 1000 RPM for each 8 MPH. The truck topped out at 72 MPH since the motor redline was 9k RPM. I am guessing that the question is if you can place the electric motor *before* the transmission? Or find the highest reduction diff for your Mustang that you can find, you need to keep the Revs up to keep the electric motor alive! Another alternative would be to place the electric motor next to the drive shaft with a sprocket on the motor axle pointing forward (next to the output from the transmission) and a 4x larger sprocket on the transmission output. That 4x reduction from the motor will allow you to spin the motor at a decent RPM because the drive shaft typically does around 1k RPM at freeway speed, so your motor is then doing 4,000 RPM. If that reductoin is built-in to the motor, all the better. Success, Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: cwa...@proxim.com Private: http://www.cvandewater.info Skype: cor_van_de_water Tel: +1 408 383 7626 -----Original Message----- From: Ben Goren [mailto:b...@trumpetpower.com] Sent: Friday, July 25, 2014 4:21 PM To: Cor van de Water; Electric Vehicle Discussion List Subject: Re: [EVDL] Hybrid Mustang: batteries On Jul 25, 2014, at 3:21 PM, Cor van de Water via EV <ev@lists.evdl.org> wrote: > Why on the world would you need over 200kW unless you are doing a race > car? Well, each AC-51 is rated for ~80 kW; I'm assuming a pair is ~160 kW -- which is about the same as the 260 motor in the car already. Seemed to me that that it doesn't make sense to have the motor(s) wanting more electricity than the batteries can deliver, so I've been trying to reach at least 180 kW...but maybe that's not the way I should approach this? Um...maybe I should back up again. The only practical place to add an electric motor is along the driveshaft, after the transmission and before the differential -- which means a direct-drive setup. It's my understanding that that means lots of electric motor to be able to live with the gear ratios, with a pair of AC-51s or WarP 9s as the likely candidates. Based on that, I assumed that the batteries would, in turn, have to supply as much electricity as the motors could take -- else there wouldn't be a need for so much motor in the first place. > My suggestion: use half your pack size (are there 90 Ah cells that you > can use instead of 3 strings of 60?) which gievs half the cost and > capacity, as you indicated that is what you need. See, this is why I'm bugging y'all. As many times I've been over the various pages, I've often been looking for something different each time, and I've apparently missed something yet again. <sigh /> No 90 Ah cells are leaping out at me with a quick search, but I now see CALB 70 Ah 10C cells for $80.40 here: http://www.electriccarpartscompany.com/70Ah-32V-10C-br-SE70AHA-br-CALB-E V-Lithium-LiFePO4-Prismatic-Cell-Batteries-br-USA-or-China-Stock-br-44L- 24W-81H-in-br-113-60-206-mm-br-55-lbs-25-kg_p_287.html Two strings of 45 gets 200 kW with 20 kWh at 500 pounds for $3900 -- something *much* more reasonable than anything I had calculated earlier. So...maybe this isn't hopeless after all. Thanks! ...and now back to do yet still even more research.... b& _______________________________________________ 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)
