[MLB-WIRELESS] Cray---zeeee idea.

[Julian Featherston]

Hi All

I couldn't help being a bit sceptical of cheap solar powered AP's (wind
looks
good on tall buildings / hilltops).
So here's my attempt to cost a solar power supply for 12V 290mA.

All power would be drawn from cheap deep cycle
batteries so one would charge to Max~13.6V.
Average charge would be ~13V say we use cheap
Vreg for 12V supply, average drain would be
	>13V x .29A = 3.77W/hr

It's easier to work in days so
	>3.77W/hr x 24hr = 90.48W/hr per day

charge/discharge loss ~16%, say battery power is used half the time, so
battery loss is equivalent to 8%.
	>90.48 plus 8% loss = 98.347W/hr per day

Efficient solar battery charger/regulators are expensive and very
difficult to 
substitute, but suitable ~75% efficiency models can be sourced for
~$100.
	>98.347 plus 25% loss = 131.129W/hr per day.

The people from Murdoch reckon a cell will average in Aus. winter about
twice
its rated power output in watt hours per day.
	>131.129 x .5 = 65.564W

So one would need
60 or 80 Watt rated cell 		$659 or $799
Charger/regulator		$100
Deep cycle batt			$120
Output Vreg & bits		$15
Mounting etc.			$10

60W solution $904
80W solution $1044

Plus: AP; Ants; Cable and mounting etc. whole node could easily be done
for under $2000
I'd reckon the 60W would be fine in better than average locations, the
80W probably mandatory for sheltered locations. This is cheaper than I'd
thought but involves pretty big cells (60W - 502x1105mm  80W -
502x1456mm). I'd guess the cells in this shot would be 25W each (wonder
if he's tops up the charge occasionally?)
http://www.cowmix.com/solar5/compressed/MVC00012.JPG