Solar panel/12V Batt.

Your 15 watt panel is lower quality and your system has more loss. In this area, that panel might provide 25- 35 watts a day. There would be many days it would give zero watts.

The reality is - those cheap small panels rated 15 watts rarely put out more than 10- 12 watts to start with. You then get loss through a cheap controller (if you have one), more loss when storing into a battery, and more loss yet when you invert to AC current.

Now, if you're out in the Arizona desert somewhere, you might do a bit better.

You're up against two things: The storage capacity of the battery, combined with the charging capacity of the solar cell.

As I recall, typical deep-discharge batteries have around 70 amp-hours of capacity. But you can probably only use half of that, so figure 35 amp-hours. Also, the inverter is maybe 50 percent efficient, so you're down to around 18 amp-hours, or 200 watt-hours. At 25 watts, that's 8 hours run time. Which means you should be able to run the receiver for 8 hours before the battery is down to where it needs recharging.

Now the 15 watt output of the solar cell is no doubt a bit optimistic. You need 14 volts to charge your battery, and the solar cell is probably rated at 12 volts. Also, there are efficiencies involved in charging a battery. A lot of energy gets wasted in heat. So figure you get maybe 7 watts out of the rated 15. If you have 8 hours of usuable charge time, you get around 60 watt-hours of energy per day. Which is only a little over 2 hours of run time. If you use the receiver more than 2 hours per day, your battery will eventually discharge.

As others have recommended, a bigger solar panel will work a lot better. Even going to 25 or 30 watts will make a big difference. However, if you only use the receiver a few days at a time, you might be able to get away with the 15 watt panel.

Good luck!

15 watt solar panel x 1 hour of sun = 15 watt/hours. 2 hours of sun = 30 watt/hours etc...

25 watt sat reciever x 1 hour = 25 watt/hours.

Add up the totals of each and as long as your putting in more than you take out it will work....Except, as someone else has said the inverter will use more than 25 watts to run your reciever.

So in the equasion you would need to know just how many watts your inverter burns as it is generating the 25 watts for the reciever... It may take more panels to make up the diff..

I bought a 30w solar panel from them to keep three boat batteries charged all winter. I have 2 deep cycle 136 amp/h each and a starting battery. The panel keeps them topped off, but of course I haven't any load on 'em this time of year.

• RV Solar stuff

I don't know what exactly you really want - but . . . if you want a small solar-electric system that's actually useful for something - a bigger panel is a much better buy.

You can buy a 170 watt panel for $3.24 per watt or a 110 watt panel for $3.60 per watt. What did you pay for your 15 watt panel? I bet quite a bit more per watt. One of these larger panels can be hooked to an ASC 12/16 conroller. I mention the ASC because it's the simplest and cheapest on the market for small systems. They sell new for $50, but I bought several used for $15 each and they've been great. I use them mostly for our camper when travelling and also at our cabin in the Adirondack mountains. In regard to the inverter, it all depends on what kind of max loads you want to run. An ex-farmer friend of mine comes up here to NY and camps on his old farm all summer - with no electricity. He borrows my solar equipment, so we've experimented a bit. He started out trying to get buy with two 15 watt panels and they were basically useless. He wanted to power a small TV and DVD player once in awhile, run the water-pump and fan in his RV, etc. Last year I set him up with one 120 watt panel and also let him borrow my 12 volt chest freezer. He ran everything, all summer and it worked great. One 12 volt, 120 watt Kyocera panel, one ASC 12/16 controller, a cheap Harbor Freight 3000 watt inverter ($130) and two golf-cart 6 volt batteries hooked in series. He also used the setup to keep his cell phone charged, and all his cordless power tool batteries. This may seem like more then you had in mind - but it gives you a lot more use for the money spent. About inverters - my 3000 watt Chinese inverter from Harbor Freight cost $130. It's quiet since the cooling fan is thermal operated and rarely comes on. I've used heavy power tools off of it, and also small loads including TVs and DVD players. It has far exceeded my expectations - and it draws less than 1 amp when in stand-by mode - and also comes with a remote control to turn it all the way off if desired. It runs at 95% efficiency - just as good as my high-end inverters that cost thousands.

I also suggest you price some stuff from marine-type dealers in the Florida area - their prices on solar equipment are often better that other types of solar-electric dealers. Sun Electronics in Miami Florida is one of the best I ever dealt with Link Backwoods Solar Electric in Idaho is also a great place if you not near Florida or marine dealers. Link