solar panels

hi folks,

heading north next week camping in the desert and chasing a few waves.
I have a 70 watt fridge and dual battery setup. I want to solar power the system as typically the van is stationary for a few days at a time.
Has anyone done the sums on how much solar power is needed ?
Is it as simple as 70w of solar ?

Mark
I would buy a 100 watt or even 120 watt folding solar panel from ebay (the Chinese panels are as good now as Solarex or BP of a few years ago). Make sure you do not mount it on your vehicle, but stand it away in the sun while you park in the shade. How long your batteries will last depends on their amp hour rating and how deep you will allow them to discharge. A 200 amp hour deep cycle battery should not be discharged more than 100 amp hours too often if you want it to last. Assume the fridge will operate 50% of the time and your solar panel will operate 5 hours per day while stationary. That means a 70 watt fridge will consume 6 amps for 12 hours or 72 amp hours per 24 hour day. Your 120 watt solar panel will produce 10 amp hours every hour for 5 hours or 50 amp hours per day, so you will lose 22 amp hours per day from your battery while you are stationary.
Happy travelling.
Doone

On Tue, May 11, 2010 at 10:23 AM, m.mullet <m.mullet@yahoo.com.au> wrote:

hi folks,

heading north next week camping in the desert and chasing a few waves.
I have a 70 watt fridge and dual battery setup. I want to solar power the system as typically the van is stationary for a few days at a time.
Has anyone done the sums on how much solar power is needed ?
Is it as simple as 70w of solar ?

Mark