Carnegie Mellon Honda Civic

dpeilow said:

$17k plus donor car for a 40 mile range, 35bhp Civic with 10 hour recharge time. Why would you?

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Batteries are linked to a supercapacitor, a high-capacitance energy storage device, and artificial intelligence algorithms are used to decide when energy is drawn from batteries and stored in the supercapacitor. The goal is to improve battery life.

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bolosky said:

Probably because of this:

They're messing around with algorithms for augmenting BEVs with supercaps, and they needed some cars to play with. In other words, it's a research project.

(Or, maybe I'm just trying to find a justification because I'm a CMU alum.)

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TEG said:

...There had been a lot of discussion about ultracaps on this blog months back , but it appears that Tesla isn't going to tell us everything they are considering at this point.
I have to imagine that they are considering all the possibilities for ultracaps, but may not have much to say about it until they day that (whatever they do) it is ready to show up in a product. Along with being (as you suggested) a way to accept a charge more quickly when hooking to a charger, they also offer a benefit at being able (theoretically) to capture more regen energy under hard braking that might produce more current than the regular pack could accept (on short notice).
Primary difficulties with ultracaps are wide range of voltages based on stored energy (compared to batteries which have narrow voltage ranges) and low storage densities (which may be on the verge of being solved with upcoming nanotechnologies). Also, the difficulties with quick charge are not just ability to accept charge, but also the need for extremely high current lines which are not typically found in residential areas, and can be quite dangerous...

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TEG said:

...One real reason why ultracaps in tandem with Li-Ion batteries would be a good idea is that chemical batteries tend to have limited "cycle life" with each charge/discharge cycle slowly wearing out the battery. Capacitors (on the other hand) tend to have much more capability for longevity with heavy cycling. If the capacitor can be a "front end" to a battery bank it could possibly provide the frequent charge/discharge associated with acceleration and regen braking. The battery "traction pack" could then be used to make sure the caps were kept with enough charge even when there wasn't enough regen going on. Another benefit to an ultracap front end is that the battery pack doesn't have to be optimized for max current delivery anymore. The batteries can be chosen to provide a more average current output, with the ultracaps providing the extra boost needed for short bursts of acceleration. A funny thing is that a lot of ultracap development has been done for high powered stereo systems. There is a surprising amount of similarity between a high powered stereo amplifier and a motor controller for an EV. In the case of high powered stereos you need short bursts of high power to drive the big woofers, but you can reduce the size of your battery bank if you have some "boost caps" to feed the amps at times of short term power need. Again the voltage characteristics of capacitors make it more complex to use when driving inverters to run an electric motor. I would say that the day will come when tandem (or "hybrid") battery / capacitor packs becomes commonplace on EVs, but for now the focus seems to be on pure battery packs...

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