I'm getting ready to stay a while in my wife's remote Pacific Island village. I want to add to the tiny 12V solar system we already have there. I know what the goal is, but I am not certain about what I need to do. I would love some comments.
What we have: 40W 12V panel supplying about 10W LED lights, via an old Plasmatronics 1206 6A regulator (on a fused switchboard with voltmeter and ammeter) and car battery. Car batteries are all we can get there, and even they are expensive. It's run for four years like that and the battery is still holding up ok. Obviously with such a wrong battery, it's a delicate system, and I don't want to disturb its life chances.
What we want to do: take over two permanent magnet 18V 36W fans, a 100W panel, a 9.5V 24W netbook (old tiny laptop) and maybe a 7.2Ah SLA battery dedicated to the netbook. The old 6A regulator won't cope with 140W panel output (or whatever we really get - but I guess it would be up around 10 or 11A sometimes). Could buy a new regulator, but I'd prefer not to. Same with more batteries - prefer not to. So it gets a bit devious here.
What I'm thinking (here's where I need some feedback):
1) run the two fans direct from the 100W panel. When it shines they go like blazes, when it's dull, they stop. We don't need them running via a regulator and battery. They soak up energy, so that even if the 100W panel is also connected to the existing 40W panel, the balance of the current after the fans (about 70W) can still all run through the 6A regulator (if I have to, I'd buy a 10A Plasmatronics 1210 regulator, easily installed because it has the same form factor as the old 6A one - just for headroom in case the fans stop working as a load dump). Is my logic correct here?
2) Run the netbook via its 9.5V DC charger which plugs into the 12V 7.2Ah SLA battery, which is itself charged from the car battery. I'm hazy about this. I know I don't want to load the fragile car battery with extra night-time demand. Hence the 7.2Ah SLA, which can be charged daytime but can be isolated from the system at night if I want to use the netbook. Would I need to regulate the charge from the car battery to the 7.2 SLA? Or would it be happy just connected directly to the car battery terminals? Is there anything else that's wrong with this idea, or that I need to know?
I'd really appreciate some guidance.