Hi Justin,

How long does this remote device need to operate without maintenance?
Each day your battery will see some amount of charge and discharge and
this will put some "cycle life wear" on the battery which will cause
the battery capacity to decline over time and it will eventually need
to be replaced. What kind of battery are you thinking of using?

Sean


On Wed, Apr 27, 2011 at 9:43 AM, Justin Richards
<justin.richards@gmail.com> 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
>
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