Here is a suggestion which I have made to the EV industry concerning
charging metrics:
I believe that charging time is in fact a poor and often confusing
metric. Let me explain. Suppose you have two vehicles - one with a
high capacity battery (say 20 kWh) which provides a high range (say 100
miles). Suppose we compare this with a second vehicle which has a
cheap, small battery (say 5 kWh) which provides a range of 25 miles.
(Note that in both cases, the range per unit energy is 5 miles per kWh.)
Now suppose both vehicles have the same charger (assume that the
charge rate is 2 kW). The first vehicle will have a recharge time (full
recharge) of 20 kWh/2kW = 10 hr. The second vehicle will have a
recharge time (again, full recharge) of 5 kWh/2 kW = 2.5 hr.
Based on the above, it might appear that the second vehicle has superior
recharge (2.5 hr versus 10 hr). In both cases, however, the range
gained per hour of recharge is the same - namely 10 miles of added range
per hour of recharge. This is the number which counts. How long does
one have to charge to provide a given amount of driving. The metric of
use is therefore "miles per hour" - miles of driving per hour of
recharge. If this concept makes sense to you, I suggest that you
consider using it.
This product was added to our catalog on Tuesday 25 May, 2010.
