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Old 07-20-2013, 05:20 PM   #264 (permalink)
NachtRitter
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Helga - '00 Volkswagen Jetta TDI
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Quote:
Originally Posted by jamesqf View Post
Wrong. A properly designed genset would either be running at optimum BSFC, or not at all. If it's producing more power than the car can use at any moment, the excess power is diverted to the battery (and if the car needs more power, it comes from the battery). If the battery is above a particular charge level, the generator shuts down.
Fine, you can argue that, but now you're opening the door to a properly designed pusher, which could also be designed to run at or near optimum BSFC (using CVT) while pushing and shut off otherwise. And there's no way to validate one vs the other because neither exists from which to pull real numbers. As well, you've removed any "plug&play" ability with the genset... the EV must be designed to work with the genset, whereas the "properly designed" pusher is self-contained and would work with any EV (well, any EV that has a hitch).

But lets go down that path a little bit... a "properly designed" genset where we use the Leaf as the sample EV... Since the Leaf isn't designed to be charged and driven simultaneously from the factory, I would assume that modifying the entire BEV system to handle the capability you describe would be a significant undertaking... but let's say it's possible. So what size genset are we talking about...? Large enough to offset the constant consumption of the EV while traveling at 65mph? Then you're talking at least 20kW... that already consumes more than the pusher in gph, even assuming it is running at it's peak efficiency. Or smaller, so that some of the EV consumption is coming from the pack and some from the generator? Even a 15kW generator is consuming 1.6gph, more than the unmodified pusher under the same conditions, and then the battery pack still limits your range.

EDIT: It's not until you get down to a 12.5kW diesel generator that you get to a consumption rate that is equivalent to the unmodified pusher (genset consumes ~0.9gph)... with that, you may be able to roughly double the range of the EV but that's not all that impressive with the Leaf's original battery pack range of 75 miles... and we still haven't accounted for the additional load that the trailer puts on the EV when accelerating or climbing... yes, it's partially offset by the regen, but since regen is lossy, not entirely.

So even such a magical "properly designed" genset is not able to outperform the unmodified pusher... if it's already losing against an unmodified pusher, I wouldn't expect it to compare favorably at all to a magical "properly designed" pusher.

Again, if you have a real world example where you can show that the genset outperforms the pusher from an efficiency standpoint, I'd really like to see it. The focused "corrections" aren't really doing it. "Unicorn" scenarios aren't going to do it either, especially since similar unicorn solutions can be applied to both sides, and nobody can validate the solutions with any real world numbers... so there's really no point in going down those paths.

Last edited by NachtRitter; 07-20-2013 at 05:36 PM.. Reason: Added add'l generator info
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