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Old 05-13-2012, 10:49 PM   #64
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Member#: 95600
Join Date: Sep 2005
Location: Pittsburgh
2003 WRX wagon


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.

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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