My figures are probably high since it dawned on me when you said that, that I was including the charging inefficiencies. I don’t have my PakTrakr yet which I can then use to do a true battery energy use calculation. The 240wh/mi estimate is my true cost at the meter value.

Coal_burner:

You’re right. A set of these batteries to run a car 40 miles would have a per battery draw much less. I wasn’t thinking of that part. The Tesla Roadster has a very small per cell draw because of its 6800+ cells. Just what you are saying.

kevin fitzgerald:

Anything which takes energy because of the motion of the car will rob the car of momentum and hence the motor will work harder to compensate. The generator will not be even 100% efficient so it will cause a net loss. For example, if you have ever ridden a bicycle with a generator light you know it takes energy to turn the generator: it is harder to pedal. After a ride feel the generator and it will be warmer than the air temp. This is part of the lost energy in the generator. One way to recapture energy is in braking. The electric motor can be turned into a generator to slow the car down and put energy into the batteries.

You’re using 240wh/mile at 30mph? That seems kind of high. The converted Priuses are getting much better than that.

http://privatenrg.com/#Bill_Moores

Alot of things pull more amps than my weedwhacker does, but not off of such a small battery. If the battery in the volt is big enough to run the car for 40 miles all electric, then depleting the battery pack would take alot longer than 5 minutes. The rate of discharge would be much in the volt than in my tiny comparison.

The a123 Dewalt pack has 3.3V x 10 cells x 2.3Ah = 75.9Wh. I have a small 3-wheeled EV (http://www.austinev.org/evalbum/1328) which uses about 240Wh in 2 minutes driving at 30mph. This means it consumes energy roughly 8 times as fast as your weed whacker. A PHEV in electric only mode will consume at least as fast as my EV does. Heat is definitely something to be concerned about.

David

If we can keep our eye on the prize we can rid ourselves of oil once and for all. Eventually we will only need to plug in once a week.

It isn’t so much a matter of keeping temperatures under control during charge/discharge, as it is a matter of extending the batteries’ calendar life. Lithium ion cells tend to lose a certain percent of their capacity every year regardless of how much they are used. This can be strongly minimized by keeping the cells cool. Now granted, the “decay” of some of the newer chemistries isn’t fully known yet, but GM probably wants to play it safe by cooling the cells below ambient temperatures.

If you chose to cool the EnerDel cells to below ambient as well, you’d need liquid cooling.