Comments on: MPGe of an electric car, revisited

By: Alex Willmer

Alex Willmer — Thu, 17 Jun 2010 01:50:45 +0000

@student Sorry for replying so late. If your refer back to my first post, you’ll see I did include UK grid efficiency of 92%, which I obtained from the Digest of UK Energy Statistics 2008. I had assumed the 20.63 kwh/100 km for the Mini E includes plug-to-wheel efficiency. That assumption may be wrong, I’ll need to look into the matter further. Mike’s numbers do account for plug-to-wheel efficiency, at 2:45 you’ll see the watt-hour meter that he used.

Agreed on the point about winter strongly affecting kwh/km, and hence range. I tried to cover how variable kwh/km is, and how sensitive it is to conditions and driving style, but were I to do it again I would state it more explicitly.

By: student

student — Mon, 07 Jun 2010 04:23:22 +0000

You didn’t calculate for plug-to-battery efficiency or grid efficiency. Typical EV plug-to-battery efficiency is currently around 70%. Most EV manufacturers, including BMW, are very coy about their EV’s plug-to-battery efficiencies and have sidestepped the subject (charger efficiency is not the same as plug-to-battery). I’m not sure about in the UK, but in the U.S., average grid efficiency is 93.5%

Also, BMW has said normal driving range for the Mini E is between 70 and 100 miles. In the winter, one Mr. Beesley experienced 40 mile range at below zero temperatures. Thus there will be a range of emissions.

You may wish to revisit the calculations.

By: drivin98

drivin98 — Fri, 19 Mar 2010 11:41:56 +0000

One might also keep in mind that as oil become more difficult to get, it becomes more CO2 intensive. The grid, with its lessening of dependence on fossil sources, is becoming less CO2 intensive.