From: Bob Siebert (Energy Efficiency)
Date: 23 Jan 1997

Dave:

To charge an EV1 using a 3.5 ft. by 4 ft. solar array (the area occupied by
two Siemens PC4-JF 75 Watt modules), one makes a few assumptions and then
arrives at the answer.

Assumptions:

   1) Assume flat mounting.

   2) Use average day length, i.e., equinox day; and then
      estimate 4.5 hours/day of "equivalent" full power output.
      (The energy that would be obtained in 4.5 hours on a
      tracker is obtained in a day with flat mounting at this
      time of year.)

   3) Array output = 150 W @ 25 degrees C or about 135 W @
      45 degrees C module surface temperature.  So,

         150 x 4.5 = 675 Wh/day @ 25 degrees C
         135 x 4.5 = 607.5 Wh/day @ 45 degrees C

   4) Assume a dc:dc converter efficiency of 95% (generous, but
      this is a custom-made converter).

   5) Assume the EV1's battery capacity is 16 kWh.

   6) Assume a charge requirement is to get the battery from 80%
      depth of discharge to 20% depth of discharge, i.e., 9.6 kWh.

   7) Thus 675 (@ 25 degrees C) x 0.95 is to one day as 9600 wH
      is to "X" days.  And...

         X= 15 days @ 25 degrees C
                     or
            16.5 days @ 45 degrees C

Figure about 20% shorter mid summer; 40% longer mid winter.

And, always park in the sun!

Bob