Quote:
Originally Posted by JSH
Capacitors are good for that usage but the problem is that only allows for start / stop function. It doesn't have enough energy storage to provide a boost for acceleration or run HVAC while the vehicle is stopped. Customers hate that type of system and often turn them off. (Nothing like sitting at a light on a nice hot and muggy Alabama day and having the HVAC blow hot air at you.)
(The EPA requires a stop / start system provide 1 minute of heat on a 30F day. There is no requirement to provide A/C with engine off.)
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Very true. Pros and cons.
Running the HVAC with the engine off means you'd need an auxiliary electric motor. Adding boost acceleration means you'd need another auxiliary electric motor. Sounds like you're pretty much at a full hybrid by that point. All you'd need is to have two motor/generators for the drive system, one for starting and charging and the other for acceleration and deceleration, and then you'd have a full hybrid capable of turning off the engine even during deceleration or low power acceleration.
A start-stop system that only has a high recharge rate via the "alternator" into a capacitor around 50V during deceleration would be simpler and cheaper. But yes, it wouldn't give you those advantages you mentioned.
It also can have an effect on the second hand market. A used 15 year old Prius, for an example, is the kind of car only dedicated afficionados can appreciate. For anyone else, finding out that they now need a $2,000 OEM battery once it goes bad they usually instead get a $600 one that lasts them a year or two if that, or go through the whack-a-mole stage. The complexity, cost and lack of longevity leads to frustration.
The same may be true of lithium ion higher voltage batteries for start stop systems or full hybrids. At some point they're going to die. The smaller they are the higher their charge and discharge rates and the lower their longevity may be. Not that super capacitors can't die either. But on the surface it seems they should outlast their lithium cousins in such a case. I guess we have to wait to see what small lithium ion packs will do. I would avoid Nissans at all cost on this one with their history of lithium ion in cars.
What I want to know is how to convert my 12V battery to LiFePO4 and get it to work without breaking the bank and without killing the battery. Seriously I do. But the complexity of thermal and battery management is holding me back.