## Thursday, January 24, 2013

### What would you do if every gas station in your area was limited to dispensing gasoline at only half a fluid ounce of fuel per minute?

As ridiculous as that sounds, that's what the average charge time for a Nissan LEAF or Chevy Volt is when compared to a Toyota Prius.  The math is simple when you consider the Prius may be getting 50 mpg or more (I got up to 66.6 mpg when I rented one while CO2 Fre was being repaired a couple weeks ago).  Compare that to about 4.0 mikWh in the average LEAF or Volt during Winter when our batteries are straining to keep their capacity.  When you consider LEAF and Volt both fuel at about 3.3 kW it's clear that 4.0 mikWh×3.3 kW is 13.3 miles per hour of charging.

Now, if that same 50 mpg Prius was fueling at a rate of 13.3 miles per hour, or 0.222 miles per minute, with each 50 miles representing one gallon of fuel, then 50 miles would take 50 mi÷0.222 mi per minute or 225 minutes (3¾ hours) to fill just a single gallon!  Since there are 128 fluid ounces in an American Gallon, dividing 225 by 128 gives 1.758 minutes for each ounce or the reciprocal 0.5688 ounces per minute.

And a 30 mpg car wouldn't fuel much faster (the more fuel efficient a car the less gasoline it needs per mile and thus the less time required to fill up enough to go that mile).  If we replace 30 mpg in the above equations we get:

(4.0 mikWh)×3.3 kW÷(30 mpg) = 0.9387 oz per minute.

And that's with a Level 2 charging station; at a standard, Level 1, US NEMA 5-15 wall outlet, 1.44 kW, the fueling rate diminishes to a mere 0.2458 oz per minute for the Prius or 0.4096 oz per minute for the 30 mpg Internal Combustion Engine vehicle.