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Old 05-13-2012, 10:49 PM   #64
sxotty
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Join Date: Sep 2005
Location: Pittsburgh
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2003 WRX wagon
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Quote:
Originally Posted by shikataganai View Post
Tesla quotes 86% charging efficiency for their Roadster's 53 kWh battery + charger setup, see link below. They also quote 0.215 kWh/mi energy efficiency for said obese-Lotus Roadster, so I feel the combination of my 90% charging efficiency estimate for the smaller RAV4 EV pack and 0.440 kWh/mi energy efficiency for the larger, heavier vehicle probably are close to reality, if not a bit conservative yet.
There is a lot of overhead that isn't related to size. In other words the smaller pack may have a smaller thermal management solution, but it takes less charge so 85% will still be a good number. Further that is only if you plug it in and charge then immediately drive off. The roadster had a lot of vampire draw after it is charged.

Quote:
By discount rate do you mean the value of the money not spent up front for the EV in the gas scenario? With savings accounts yielding 1.1%, if that, it's not such a big concern to me.

12k miles over a year works out to 32 miles and change per day. That's certainly possible even with the charge-only-at-home scenario that must will adhere to (my guess).
I am just saying that is the proper way to do cash flow problems. You used a discount rate of 0. Since it is a personal discount rate that is fine maybe that is yours. But as you note a bank is 1%, CDs are higher, bonds, etc... there are many options. Businesses use something north of 10% usually. Consumers exhibit wildly varying discount rates because they won't buy efficient refrigerators, but save money in low yield accounts. The reason for this is likely a bunch of things, but one of the main ones is most consumers have no idea about what a discount rate is or how to calculate the time value of money.
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