Smallest solar panel setup for emergency power!

December 28, 2006

One reader, Mike, brought up the point of having more complexity - more parts - as the trade off for cheaper, and that is true. If you click on the picture of the panels you'll see that they measure 3' by 3' assembled with an output of 45 watts. Panels that put out 85 watts are 3.5' by 1.2' (I'm approximate here - need to check). So these panels are very inefficient considering the amount of space they take up. However, the cost per watt comparison, the smaller 85 watt panel costs about $5.11 per watt (at the best price I can find) and the thin film type from Harbor Freight (China), is $4.44/watt. The white square in the corner is a piece of 8.5 x 11" paper to give you a frame of reference.

This is the inside of the electronic charge controller that comes with this kit. In the price per watt comparison above I did not factor in the frame for the panels, the charge controller and two lights. I did not because if you read down in our pilot project below, TJ feels this would be better off scrapped, and instead to use an inexpensive charge controller that is available from Harbor Freight for $30. We may find a use for this box, possibly just as a direct DC source for many of your 9V, 6V, and 3V devices. The frame that TJ had said was weak, once bolted to the panels was sturdy. I'm going to use it on the Casa Blanca when I can find a way to ship here in Q.

Just a note to keep efficiency and price in perspective. Any solar panel is actually incredible, magic and frees you from the grid, keeps you on line when others are down, and works tirelessly, every day the sun shines, storing free sunlight for you. For example all today I've been running the satellite transmitter, modem, controller, and wireless router here in the Safari off the stored energy from one 1972 35watt panel charging some Walmart car battery. And it works, and I am free to park far from the madding crowd because of it and the others on my Safari. More important to get started in solar than worry about getting the exact right thing. Solar is additive, unlike generators. IF you don't have enough, you can add a little more here, and there, and soon you have you're own completely independent power!

December 23, 2006
TJ (Terry) drove to Harbor Freight and bought one of the cheap Chinese solar systems they have on sale for $199. He has an initial impression below. This is pretty technical and what it means at the end of the day is that it is possible that these are a great buy if we consider the cost only for the panels, and dump the electronics. The one I designed yesterday is fine except there is no control for over charging the battery. This harbor freight Chinese panel (actually a set of three 15 watt panels) may let us design a less than $500 system that has a full 90Watts instead of the 85 watts below, and would have a charge controller in that price that would make the system require almost nothing from you except to check water in the battery (batteries) once per every 2 months. So stay tuned, we're cooking on this. I'm going to order a test set to be delivered to me in Q for the middle of next week, based on Terry's recommendations. Because of some concerns of my friend Ed, we're going to flog them and see if there is something totally unsuitable about the panels themselves. Will keep you apprised.

Parts list: I'm doing some calling on the 75 watt panels to see what is available. I would like to find one for less than $400 current pricing - it is the big money here. The battery can be used if you want to resurrect one, I'll teach you how (if it is not shorted you can usually bring them back to life). The best source for large size copper wire is broken jumper cables. They break at the ends and people tend to pile them up in cars and garages. The only thing you really need if you are a good scrounger is the panel and the diode. Everything else a good scrounger can get for a buck or two (auto parts stores and tire stores take in the used batteries and have to pay to have them taken away - they usually will part with one for a couple of dollars) I'll show you how to know a good battery from a bad one later.

What will this panel give us for juice. How full is the power bucket. Can we crank up the stereo, go button down on the CB all night or what? Is this the little Bonneville I've always dreamed about? Well, yes and no.
To go farther we have to learn a bit about amp-hours. When you make your own electricity you live and die on how many amp-hours you can collect and store and use. The more you can catch the more you can use. So how many are we catching here with this little system. Of course we have to decide were you are and what time of the year it is.
If you think about it, solar energy catches the sun. You can say it catchs light, but really if you can't see a shadow cast on the ground by objects you don't have enough light to wake up your solar panel. You need sun. No sun, you might want to wait for my section on straight vegetable oil diesel generators that will run most of your whole house. You can make power with the grease from McD's french fries if you want. However right now we're talking sun light. But with sunlight, we have a way to measure how much we catch over time. Your 85 watt solar panel is rated at 5 amps at 17 volts DC (it has to be higher voltage than the battery which is 12V in order to charge it). If we multiple the number of hours of sun by the 5 amps we know how much electricity we can gather and store in one day. If we assume 8 hours of sunlight we can guess that your 85 watt panel can capture 40 amp-hours of electricity in one day. I know this is very crude, and soon you will become a solar sophisticate, arguing the merits of various wire sizes, sine wave inverters versus modified sine wave, and of course, become a battery conessiuer. But the important thing is to just get started. you can add, and adapt and increase in size and sophistication later. This will work, day after day, and supply emergency power as well as some free to use power day after day. I know you want to build it now, so first the diagram and then the build it instructions. At the end we will talk about how much of your 40 amp-hours you get to use and how much you lose, and things you can run. First we have to-

Build it!

1. Aim your panel due south, on your roof, on your car roof, on your RV roof, on your bicycle cart, on your storage trailer. If you can mount it so that it can be brought up to a 45 degree angle (and you live in the USA) make sure you point it south, and if you want to be totally cool, shift it towards the east just a few degrees.
Where's south? OK this is the homework. Watch where the sun comes up and where it sets. In the middle of the two is where you should point your solar panel. That is south.

2. There are two wires to be connected to the panel. One has the electrons that flow out. It is going to go to the battery. The other one is how they flow back in. The more sun, the more of the electrons and when we get a bunch ready to go down the wire - that is our amps. How much they want to go down the wire - how bad they are pushing down the wire, that is voltage. The work you can do with the electricity is the voltage pressure (volts) and how many electrons (amps) multiplied together. We call these two multiplied together WATTS. So you can say Voltage times Amperage equals Watts. To be cool we abbreviate all that as VA=W.

In the diagram I drew above- Between the battery and the inverter it should be short - like less than 2 feet, less than 1 foot if you can. If you just laid all this out on the ground with the solar panel facing up it would work. After that we're just talking pretty, more convenient, but that is how simple a solar system is. The parts list had you buy some or scrounge some battery jumper cables. Use them for all the wiring show. You're going to have questions on that when you go to make the connections as the wire is too big to connect to the connectors on the solar panel and on the inverter. That's OK, just solder or crimp to smaller sized wire in the last inch or two. The thicker copper has less resistance and therefore more of your amps make to the battery and then to your inverter, then to your stuff - like that CB radio, or the walkie talkies that keep you in contact with your family and the world.

3. If we connect the hot lead (the one with the amps that want to come out) directly to the positive pole of the battery - and thus fill up the battery. That is GOOD. But now the sun goes down and all the amps stored in our battery now come out and go back through the solar panel the wrong way. Oops. Dead battery in the morning. So we use a diode which is a little gate that won't let the amps go backwards through your expensive solar panel.

4. So now have a charge up battery. How do you get to use the 12V when everything, or most everything says it's 120V or 110Vs? We use a device that turns the 12V into 120V of the kind you need (Alternating current - don't worry - you don't have to know it to do it). That device is called and inverter. There are many cheap ones, used on ebay, new at GI Joes, Walmart, Camping stores of all types. They have two wires, one to go to the red (positive side) of your battery, and a black that goes to the Negative side of your battery. They have a switch to turn them off and on so that you can leave them hooked up all the time, but if you shut them off when you're not using power, they won't eat the little bit they need to make your 120V AC power. They have one or more regular wall style 120 plugs.

5. You attach your extension cord to the inverter and run it to a cheap power strip - to give you more than one plug in, and there you have it - 120V power.