Eva’s solar pageThis page is about the portable solar system I took to Papua New Guinea to be able to charge the batteries of my computer and videocamera while doing fieldwork in a remote village.
I had trouble finding enough information on the web about a system this small so I thought I’d put some up now that I’ve worked it out. I’m actually in the field writing this on the very computer we’re talking about, and the pics were just taken using the videocamera in question (obviously, I’ll have to go to town before I can get it on the web). Note: If you won’t be using a car battery, this may not be the page for you. Components
Skip down to the » diagram.
The solar panelNow this is the niftiest thing you’ll ever have seen. It is canvas backed and folds up to the size of a biggish book, does 30W, and weighs only 1.5kg. There are different sizes (20W, 56W, etc.); you check out the pages of AltEnergyStore. I didn’t find their sales department particularly helpful and bought mine from AAPS Power at US$682 + freight (May 2004). The exact model I got is made by Global Solar and is called Portable Power Pack P3-30-60, 30W, for 12V. The only drawback is that it is not marked for positive and negative poles on the output cable, so you have to check that (the car mechanic mentioned below will do it for you). 30W seems in fact to be more than I need, at least with the tropical sun. I can charge 2 computer batteries in the night and when I gauge the battery it still tells me it is full. Might be useful for a rainy spell though. The battery and charge controllerI knew I would be able to buy a car battery locally so I didn’t bother carrying a battery here. If you are going to take a battery to where you are going you will want to get a different type (sealed etc.) but I haven’t the slightest clue about those, sorry. The useful thing about the car battery of course is that you buy it when you get there so you don’t have to carry it from home, and you can get them in most third world places. Someone will usually be happy to inherit it when you leave. The scary thing about car batteries is that they can get over-charged rather easily, produce a lot of gas and explode. This is where the charge controller gets into the picture, it prevents the battery from over-charging and prevents power leaking back and cooking you solar panel (or somesuch, sorry not too clear on this point but you definitely need a charge controller if you use a car battery or other non-sealed acid battery). The charge controller I got weighs nothing and is clearly marked for what leads need to go where. It’s by MorningStar and it’s called SunGuard, 4.5A, 12V PWM charge controller, and was US$40.
The other thing about car batteries is that they are apparently not very happy about being drained too much and too often, but I seem to be doing OK with the size panel I’ve got, relative to the load of charging my computer. I got a plastic box for my battery, as I was seriously worried about water reaching it or something metal falling across the positive and negative poles and short-circuiting the whole thing, or me just being stupid and touching both poles at once. (This one is made for a car battery; if you get a random other box, make sure there is some ventilation.) Lighter socket and car adapters – a 12V systemI decided to get car adapters for the equipment I want to charge. These are the things that go into the cigarette lighter socket in a car so that you can charge your stuff while on the road. They are normally produced by the manufacturer of the equipment itself and tend to be apparatus-specific. They run off the car battery, which is 12V, so you do the same thing here, only omit the car. You can get a used lighter socket from a junk yard anywhere in the world. The trick is to work out which bit is positive and which is negative, you don't want to cross the cables! Any car workshop could probably do that for you, using one that is installed in a car. Mine has the positive pole at the bottom of the socket where the tip of the plug goes (maybe all do?), and the negative pole in the metal cylinder of the socket itself. If you want to use your normal charge adapters you first have to convert the power to the voltage they need (110V or 220~240). This means getting an inverter, which will consume some percentage of the power your solar panel generates (up to 30% I think; the car adapters may take a little too, I’m not sure, but it will be less). Switch and fuseThe switch and the fuse were invented by Joe, the mechanic who connected it all up for me. He installed them on the positive lead between the battery and the lighter socket, so that if there would be a power surge the fuse would blow, and the switch lets me connect the computer with the power off, then turn it on when it’s connected. WiringWarning: if you stick the panel on the roof or anywhere that is above the battery etc., rainwater will follow the lead down, which is not good at all. Make the lead dip so the water runs off away from the battery. I didn’t trust myself to connect it all right, so I got Joe, a local mechanic in Kavieng to do it for me, and he did a great job. It’s useful to get someone who understands electricity to size the wires for you. My equipmentIn case you want to compare your equipment, I have:
I also have a meter for checking the charge level of the battery (if you want to be fancy you can get one that connects to the battery which gauges it all the time; the one I have is just a meter with two prongs that you hold to the positive and negative poles when you want to know – the useful thing about it is that I can check regular torch batteries etc. with it too). Naturally you want to make sure your meter has the relevant voltage ranges for the types of batteries you want to check. Diagram
Go back to the » text about the components.
PhotosGo to the » photo page!
Page created 30 July 2004
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