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This thread is too good to pass up.

I have a Dell laptop which contains a 2300 mA-hr battery (or 2.3 A-hr). 2.3 A-hr is the amount of energy that a fully-charged battery contains and is equal to 8280 A-sec. If I bring the battery from fully-discharged to fully-charged in 9 seconds at a constant charging current, I would need to supply 8280/9 A or 920 amps to the battery for 9 seconds. Furthermore, this 920 amps times 14.8 volts represents 13,616 watts power for the 9-second charge time. Mucho amps and lotsa watts!

How big would the connecting wires need to be to carry this huge current? The largest gauge copper wire in the American Wire Gage standard is number 0000 which is 0.46 inches in diameter and is rated for 380 amps; you would need to connect 3 of these huge wires to each battery terminal to keep from exceeding the wire current-carrying capacity. Of course that much current would vaporize the terminals.

The 920 amps is DC but it could be converted from house current AC by using a power supply. A 120-volt wall circuit can supply 15 amps maximum at 120 volts or 1800 watts. Clearly, if you need 13,616 watts and only 1800 watts is available from your friendly local wall socket, you would come up short. If I got AC from the heftiest circuit in my home breaker box (30 amps at 240 volts), that would provide only one-half of the power needed to charge my laptop battery in the 9 seconds!

Of course, if I ran 920 amps into my laptop battery it would explode. Period.

Someone brought up the Prius. My sister has a Prius and I checked the owner's manual which lists the auto's specifications. According to my calculations, the Prius can run on the battery pack for only two minutes! The gas engine has to almost constantly start, run, and stop to recharge the battery. Her car does get an honest 45 MPG which I attribute to two factors: The engine runs at a constant speed to charge the battery pack (at optimum efficiency) and the Prius wheel motors turn into generators when you slow down, using the car momentum to recharge the battery pack.

"Her car does get an honest 45 MPG which I attribute to two factors: The engine runs at a constant speed to charge the battery pack (at optimum efficiency) and the Prius wheel motors turn into generators when you slow down, using the car momentum to recharge the battery pack."

Close. It uses an Atkinson cycle variant of the common Otto-cycle internal combustion engine. That yields about a 15% efficiency gain right there. The peaky personality of these engines would render them undrivable if it weren't for the clever differential-like electronically continuously variable planetary gearset, which as you say maintains the engine in a narrow speed band for maximum efficiency. Regeneration is another advantage, as you also point out. But then there's another thing: the gas engine need only be sized for pulling the car at-speed. For burst-power needs, the electric motor contributes. So the gas engine doesn't need to be oversized in order to accommodate acceleration, passing and hill-climbs. As a consequence, the Prius is quite a drivable vehicle. It is also very roomy, seating four adults quite comfortably and five when needed, with a cavernous cargo area. And one last thing: the a/c is electric, so the engine doesn't have to run at idle at stops in order to keep the cabin livable. (Flip side: since the engine's coolant provides heat to the heater as with all other cars, turning the heater setting up can make the engine start to run!)

Lots of Freepers get all gruff and dismissive about the Prius because it's, well, kind of the ultimate Al Gore-mobile. But it's a nifty car, very easy to live with, and competitively priced compared to others with equally capacious cabins.