Another thing I forgot from my last email - I am no expert in solar power but I don't see any consideration of the average insolation (both due to latitude and weather) at your location. Have you taken that into account? On Wed, Apr 27, 2011 at 9:43 AM, Justin Richards wrote: > I need to size a solar install to remotely power a 3G Modem and a > Intenna (Intenna is an enclosed wifi antenna with =A090 mW UltraWAP). > > Total current draw at 12v is 0.5amps. =A0I will base my calculation on 1 = amp. > > Below are my calculations which include some assumptions which maybe > incorrect. =A0Therefore I welcome any corrections or suggestions. > > Location Lat=3D-28=B0 =A0Long=3D+122=B0 > > Winter Solstice 21/06/2011 =A0Rise 0642 =A0Set 1701 =3D 10:18 hours dayli= ght > =3D 7 hours usable hours. > > Worst case battery drain for 1 day =3D 1 amp current draw for 17 hours = =3D > 17 amp hours. > > Considering 50% charging efficiency requires 34 amp hours to recharge bat= tery. > > Total Amp Hours =3D 34 amp hours + 7 amp hours =3D 41 amp hours > > Over a 7 hour period =3D 41/7 =A0~ 6 amps. > > Power =3D 6 x 12 =3D 72 watts. =A0Considering solar panel not working at = MPP > need to add margin guess 10% =3D 80watt panel. > > >From above, 17 amp hours discharge during dark period. =A0Batteries > Availabale in 18amp hr and 40 amp hr. =A0Choose 40 amp hour. > > Summary > > To power 1 amp continuous at 12 volts requires 80watt solar panel > mounted at 28=B0 with 40 amp hour battery. > > Does this appear to be a reasonable selection. > > Cheers Justin > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .