Wed May 29 00:28:23 PDT 2013

keeping my ass warm

So I was reading the owner's manual for the 2013 Nissan Leaf, (as you do) because I was wondering if it said anything about overuse of rapid charging.

Every time I bike to the grocery store, I see a Leaf connected to the 440V DC fast charger, (Google Kirkland is five minutes away.) which can put an 80% charge on a car in 30 minutes.

But batteries suck. Charging a battery in 30 minutes in precisely analogous to discharging it in 30 minutes-- something big lithium-ion batteries don't like. Sure enough, page 43:

Batteries don't like to get too hot or too cold, to be discharged too hard, too deeply, or left discharged for too long. You might then conclude that the best choice is to just leave the car in your driveway-- where the battery will then just quietly decay on its own. Batteries suck.

Also, page 187:

This makes a lot of sense-- heating pads are orders of magnitude more efficient at warming humans than using air as the transfer fluid. In an internal-combustion vehicle, you get hot air for free, since a heat engine has to dump a lot of heat to the outside environment in order to extract useful work from it, you might as well pass that waste heat stream through the cabin, like a not-terribly-efficient cogeneration setup.

But in an electric vehicle, every watt-hour of power comes from the battery pack, and each watt-hour is dear indeed. Heat is no longer free.

Bold prediction: Heated seats will be standard equipment in all electric cars.

Posted by Samuel Bierwagen | Permanent link | File under: Engineering