Here's a small solar charged emergency power box I built up with an old 80 watt solar panel and some retired burglar alarm batteries. It sits on the back deck and just keeps the batteries charged. It'll provide enough power to recharge USB devices and run a laptop for a while.
The batteries and controller fit in a plastic box that sits behind the solar panel, which lives in the back deck.
Given that the system is never under any real load it does not need to be facing the sun directly. So our west facing deck is good enough.
The battery box is small enough to carry in one hand - so it's easily transportable.
The 80 watt panel is bigger than needed - but I had it spare, so it might as well be doing something!
- 80 watt solar panel
- 4 x 7amphour 12 volt sealed lead acid batteries (retired burglar alarm batteries). I'm guessing they have half the capacity of new cells - so the full pack should hold about 18 Ahrs (0.22 kWhrs)
- 12V 10A Solar controller/regulator US$14 with free shipping to NZ
- 12 volt car socket
- 12 volt to USB charger
- 12 volt to 230 volt mains inverter 150 Watts
- Red LED Digital Panel Voltmeter DC 0-30V
- old speaker wire to connect the solar panel to the solar charge controller (could also use the mains wire from a dead vacuum cleaner)
- old power cord wire to connect the batteries to the solar
- female spade connectors to connect to the batteries
- screw terminal strip
- clear plastic fishing tackle box
I upgraded the battery and charger to lithium.