I need to size a solar install to remotely power a 3G Modem and a
Intenna (Intenna is an enclosed wifi antenna with  90 mW UltraWAP).

Total current draw at 12v is 0.5amps.  I will base my calculation on 1 amp.

Below are my calculations which include some assumptions which maybe
incorrect.  Therefore I welcome any corrections or suggestions.

Location Lat=3D-28=B0  Long=3D+122=B0

Winter Solstice 21/06/2011  Rise 0642  Set 1701 =3D 10:18 hours daylight
=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 batte=
ry.

Total Amp Hours =3D 34 amp hours + 7 amp hours =3D 41 amp hours

Over a 7 hour period =3D 41/7  ~ 6 amps.

Power =3D 6 x 12 =3D 72 watts.  Considering solar panel not working at MPP
need to add margin guess 10% =3D 80watt panel.

>From above, 17 amp hours discharge during dark period.  Batteries
Availabale in 18amp hr and 40 amp hr.  Choose 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

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