For your hybrid application, I'd go with the AC. One word: regen -- without it to recharge the battery, "hybrid mode" is of little benefit; better to just disengage the motor altogether.
I get decent performance out of my Porsche 914 with a single 9" DC motor in 3rd gear (although it tops out around 65MPH). It even starts and drives OK in 4th, but the clutch begins to slip. The lower gear ratio Netgain suggests will keep motor speed down, making it easier to to push current when the engine is spinning the crankshaft at higher speeds. However, running slow comes at the expense of the torque multiplication in your gearing; ultimately, you'll be running the motor hot in a low-efficiency region. My Porsche performs as it does because I have a 170V pack and a 1000A Zilla, but each of those drives up the cost & complexity. At lower voltage, I'd be much more dependent on the gearing to have any power at speed, and at lower currents, I'd be much more dependent on the gearing to provide starting torque. And when I actually use 2nd-4th gear, it's a lot more fun/powerful throughout. The AC has a better torque profile for a fixed (albeit higher) gear ratio. However, given the rating of the motors, you'll probably need two AC-51's to get decent performance unless they're upstream of the transmission. As for the hybrid mode, I would strongly encourage you to take it incrementally, because the controls will be a challenge and you don't want to be kept off the road while you figure it out. The vacuum sounds like a good idea, but my gut says you'll need inputs from the throttle too. You'll almost certainly require a control processor (possibly Arduino, possibly more powerful). Step 1, IMO, is to make the car work with an EV mode and with an engine-only mode where the electric motor just spins freely. Once you have that working, you can tinker with hybrid control schemes all day long. Frankly, I think it will be a game of diminishing returns. Since you're using the existing engine instead of an undersized one that relies on the electric boost, and since your motor is fixed on the driveshaft (meaning you can't regen without also burning energy in compression braking), I think the fuel efficiency gains will be limited. I would say you should think of it more like a Honda Civic hybrid than like a Chevy Volt/Prius, except it will have the ability to fully disengage the engine for EV-only drive. -Ben On Jul 23, 2014, at 5:02 PM, Ben Goren via EV <ev@lists.evdl.org> wrote: > I know the question of AC and DC motors is a controversial one, and probably > done to death. But if all y'all might humor me, I'd appreciate a bit of > guidance on this. > > To recap, I have a chance to buy a 1964 1/2 Mustang in good shape for not > much money. The goal is to get something not unlike the driving experience of > a Volt, with an all-electric range of roughly a couple dozen miles and a > "traditional" Prius-style hybrid range limited only by the gas tank. The > thought is to replace most or all of the driveshaft with one or more electric > motors. > > I've now spoken with somebody at both HPEVS and Netgain. > > The guy at HPEVS wasn't exactly enthusiastic about the plan, but thinks it > can be done. He recommends a rear differential ratio in the 6:1 range to make > an AC-51 not be miserable. That would require a new 9" rear end for the car > and a custom transmission geared appropriately taller to keep the combustion > engine happy. He doesn't know much about people doing direct drive or hybrid > stuff with HPEVS motors. > > The guy at Netgain was most encouraging, and has done something nearly > identical to what I have in mind. He didn't recommend any gearing changes; > indeed, he suggested that a higher ratio (3:1 or higher) might be better than > stock, instead of the other way 'round. He had many very helpful suggestions, > such as ways to couple two motors or to get the electric motor(s) to supply > most of the power at low speeds and little power at high speeds, thereby > maximizing overall gasoline economy. > > It seems the beaten path for this type of project is therefore a Netgain DC > motor...but I still like the regen capabilities of the AC motors and the > reduced maintenance. > > I'm aware that only limited efficiency gains are available with regen, but I > have a secondary concern. When running in hybrid mode, once the batteries get > depleted, the car would become a pure-gas vehicle. It'd be nice to instead > use the combustion engine to just barely recharge the batteries enough to > still provide acceleration assist -- the same way the Prius and the Volt do > things. With regen, that should be straightforward. Without, I'm left > thinking of kludges such as using the combustion engine's 12 volt system to > trickle-charge the electric motor's batteries, and I'm not so sure that's > even safe, let alone possible. However, as a practical matter, this might not > actually be a concern if a full battery charge would be comfortably ample for > a full day's worth of hybrid-mode city driving. > > So...I'd appreciate a bit of insight on all this. Would a pair of AC-51s be > as happy in a direct drive application as a pair of WarP 9s, despite the > HPEVS guy's lack of familiarity with the matter? Am I worrying too much about > regen and brush maintenance? Is there something else I should be worrying > about instead? > > Thanks much, > > b& > -------------- next part -------------- > A non-text attachment was scrubbed... > Name: signature.asc > Type: application/pgp-signature > Size: 801 bytes > Desc: Message signed with OpenPGP using GPGMail > URL: > <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140723/4e0f8876/attachment.pgp> > _______________________________________________ > 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) > _______________________________________________ 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)
