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 Cor16.5 days @ 45 degrees CFigure about 20% shorter mid summer; 40% longer mid winter. And, always park in the sun! Bob