i want to know if this solar panel would charge a 12v car battery and how long would it take..?

Hey Josey, if that panel says it is for 12 volts, it is most likely wired to put out an open circuit voltage of 18 volts, which is fine. At 10 watts, its maximum current will be less than 1/2 amp. Hooking this sized panel, or even 2 or 3 of them directly to your battery will not cause an overcharge regardless of how long they are charging. The output voltage will simply degrade to the battery's charging voltage curve, which at 1/2 amp will probably never exceed 13 volts. If you want to learn more about this, look for a book in the library called, "The Complete Battery Book, " by Richard Perez. Richard happens to be the founding editor of, "Home Power Magazine," a periodical worth the annual subscription if you are trying to learn about these things. We started subscribing 13 years ago, 12 years ago we went to the energy fair in Wisconsin, and today our home is completely powered by the wind and sun.

As far as your lights, most garden sized LED lights use less than 1/3 watt, which works out to less that 1/10 of an amp each. You could conceivably run 8 of these things for 4 hours each night on the power that little panel should make in one sunny afternoon. I'd say try it, keep an eye on the battery voltage for a week. If it is not getting back up above 12.7 volts each day after running the lights at night, then go for a second panel. A car battery is fully charged if you leave it alone for several hours, no charge and no usage, and the voltage is 12.6 or higher. Again, Richards book really describes all the specifics on this. Any battery can take a continuous charge equal to 2% of its amp hour capacity and never overcharge. Any good quality car battery will be at least 40 amp hours, usually more, so at 2%, that means you cold charge it at .8 amps and never overcharge it.

If you really decide to get into this in the future, one of the best batterys for this is the golf cart battery. They are made to run down each day, then recharge each night. They only come in 6 volt sizes, so you'll need two hooked in series. Then you have a 220 amp hour pack. You can connect up to 75 watts of solar to a pair of these without any charge controller. We have a set at our cabin up north that runs all the main floor lighting and our electronics, all on a 53 watt panel, been working that way for 11 years. The lighting is all LED, a link below will take you to them. If you are really interested, subscribe to the magazine, then use their search engine to look for an old article called, "Small System First." It is actually an article about our cabin they ran years ago for people that want to get into solar in small bites first. One word of warning, try not to get too much information from hacks like us online, one thing I've learned over the years is that there are two things in vast supply in solar power, the sun, and missinformation. Symtex's answer about your panel not having enough voltage is an example. When a panel manufacturer says a panel is 12 volts, that is the nominal voltage, which matches the battery and items it is powering. All 12 volt panels are wired to put out a higher charging possible voltage, usually 18. Take a look at your panel and see if you can count the individual cells inside it. Divide the number of cells by 2 and you have your open circuit voltage. Almost all 12 volt panels have 36 cells. A panel that actually put out 12 volts would be useless to almost anyone as it would not be able to charge a 12 volt battery. Take care Josey, and good luck, Rudydoo

Car batteries need at least 13V to charge them and no more than 14V. This means that your panel needs to be capable of producing at least 13V and must be regulated to 14V to prevent overcharging the battery. A car alternator is regulated to 14V as this is the ideal charging voltage. With 12V you won't be presenting the battery with a higher voltage than it contains so you won't be able to make it accept any power. You also need there to be a diode in series with the battery but the regulator is likely to perform this function too, this is to prevent the battery's power from draining back through the panel when the sun goes down.

Guide To Solar Power : http://solar.eudko.com/?rQb