How to measure "fuel efficiency" of an electric car?
 

I'm buying an electric ForTwo. Anyone know how to check for "fuel efficiency" with an electric? Thinking of doing some of these mods, but curious how to quantify the results.

[Admin note: moved this question from thread: http://ecomodder.com/forum/showthrea...4-a-26046.html ]

Doesn't the car have a built-in trip computer that can show energy consumption?

I know the Leaf does. The Bolt does.

The iMiev doesn't, however. (And considering it's a bare-bones EV along the lines of the Smart, it's possible there's no energy gauge in the Fortwo)

There are several ways and several considerations.

First, the energy drawn from the wall is more than the energy supplied by the battery because charging is not 100% efficient. Charging efficiency is normally in the 77-90% range.

Some people take the number of miles driven and divide by the number of kWh consumed. This would give miles per killowatt hours. A rough average of EV drivers is 4 miles per kWh.

You could just as easily take the kwh consumed and divide by miles, which would give you watt hours per mile (lower is better).

You'll want to do A-B-A testing with your mods to verify the results reflect real differences in the mod rather than some unaccounted for variable like wind direction, temperature, etc.

I used to measure energy consumption of the ForkenSwift at the plug.

It was easy to do since the charger was only 110 volts, and it drew less current than a Kill-a-Watt's max rating, so I simply used one of those.

http://ecomodder.com/forum/fe-graphs/graph12.gif

Another point to consider...

If you're mainly looking at doing areo mods, you can test them doing coastdown runs. Results don't care what drivetrain the vehicle has.

Aren't EVs required to have an OBDII port? (Even if much of the standard things on it are only applicable to ICEs.) So it's possible that the manufacturer has put data like current draw &c on that, Worth checking out, I think.

Yes, EVs have an OBDII port. Some of the more popular EVs have apps to tap into that information such as "Leaf Spy".