DIY solar panel question

[acornstu]

Hello,

I would like to compliment you guys on the site. It seems very informative and I look foward to going over the site in the next few days.

Now for my question: Basically, i'm planning on building some homemade solar panels. Most likely they will be made from pre tabed factory blemished ebay cells. I'm sorry to be so vague, but i am unsurea exactly what cells and contoller i will be using. I know that i am shooting for a twelve volt setup to charge car batteries and a few small deep cycle batteries. I will most likely build a panel under 100 watts and use about a 10 amp cheapo solar controller.

What i'm unable to figure out though, is how many volts my panel needs to make. I've asked a few people and have gotten answers from flat 12v all the way to 18+. I'm sure that it will mostly depend on what the controller will handle. But basically i just want a great functioning and portable way to charge batteeies from boats to cars to laptops while i'm away from a power outlet.

Sorry if i confused anyone. It's late and if i need to clarify anything feel free to let me know.

Thank you all for taking to time to read my post. And hopefully i can get this last hurdle beat.

 

[Analog]

Hello,

I would like to compliment you guys on the site. It seems very informative and I look foward to going over the site in the next few days.

Now for my question: Basically, i'm planning on building some homemade solar panels. Most likely they will be made from pre tabed factory blemished ebay cells. I'm sorry to be so vague, but i am unsurea exactly what cells and contoller i will be using. I know that i am shooting for a twelve volt setup to charge car batteries and a few small deep cycle batteries. I will most likely build a panel under 100 watts and use about a 10 amp cheapo solar controller.

What i'm unable to figure out though, is how many volts my panel needs to make. I've asked a few people and have gotten answers from flat 12v all the way to 18+. I'm sure that it will mostly depend on what the controller will handle. But basically i just want a great functioning and portable way to charge batteeies from boats to cars to laptops while i'm away from a power outlet.

Sorry if i confused anyone. It's late and if i need to clarify anything feel free to let me know.

Thank you all for taking to time to read my post. And hopefully i can get this last hurdle beat.

Those batteries you mentioned are vastly different in their charging requirements. If you're want to restrict this to just 12V lead-acid cells, look up charging circuits for that type of battery. There is a ton of information out there on those.

 

[acornstu]

Oh, i didn't think that would matter. I'll stick to the deep cycle 20ah or less batteries probly. Thanks

 

[HarveyH42]

Few thing you might not know... a 12 volt battery, is really 13.8 volts. A solar panel has a higher voltage, unloaded, than with a load attach, so you need higher panel voltage, plus there will be losses in the charge controller. Your panel voltage will also vary some, with how much sun it receives.

 

[acornstu]

Well, i've found on a couple of sites that the common way is to wire 36 cells for about 18v or so. Assumming this is correct, the only thing i have left to figure out is weather or not it is safe to charge the batteries with the controller and panels while simultaneously using the batteries to power something.

 

[Nigel Goodwin]

Well, i've found on a couple of sites that the common way is to wire 36 cells for about 18v or so. Assumming this is correct, the only thing i have left to figure out is weather or not it is safe to charge the batteries with the controller and panels while simultaneously using the batteries to power something.

Of course it's safe, and is how they would normally be used.

 

[acornstu]

Great. I though so, but since this homemade panel is going to be running electronics in a home i don't own and might be unattended at time. Hate to burn the house down

Thanks a million for the help guys. It's going to save a ton on the gas bill this winter.

 

[Nigel Goodwin]

Thanks a million for the help guys. It's going to save a ton on the gas bill this winter.

I suspect you're in for a disappointment if you think that!

 

[acornstu]

Haha, i'm not planning on covering the block with homemade panels. We have a little gas stove in the computer room that is placed right next to a few gusty windows. I'm covering up that half of the room and running my panels to a small heater instead. And if it won't heat the room, i'll use another AC heater that i know will do the job. And that little one will be on my feet!!

Don't know why, i'm fine with the house being 60 degrees, but i get grumpy when my feet are cold. Either way, i'm not running that ticking time bomb gas heater and will spend the next couple months on the computer in front of my little heater.

I shatterrd my heel falling from some rafters the other day. My girlfriend told me i could build my little heater setup if i didn't burn the house down. So, now i have something to do next week and won't be in "such a pissy mood" as she puts it.

Really, i could just crank up one heater or the other, but i feel a little more useful if i can make the room more comfortable while saving a little cash at the same time. Since i'm not bringing anything in i may as well try not to spend everything we've saved. A buddy owes me about $400 for helping do a bunch of yardwork the last few months. And it will save me even more money in the long run since i won't be cranking up the thermostat to the whole house when i feel a draft from those darn windows.

 

[Nigel Goodwin]

Haha, i'm not planning on covering the block with homemade panels. We have a little gas stove in the computer room that is placed right next to a few gusty windows. I'm covering up that half of the room and running my panels to a small heater instead. And if it won't heat the room, i'll use another AC heater that i know will do the job. And that little one will be on my feet!!

I suspect you're going to be even more disappointed if you expect to run electric heaters off solar power, you're going to need massive panels (and batteries) in order to do that - and be in a really sunny country.

If you're only looking at trying to assemble a 100W panel, I would suggest you're probably looking at a weeks worth of charging to run a 1KW (small) heater for an hour.

 

[acornstu]

Dang. Well, i planned on building five or six panels. And i was looking at about an 800 watt heater, but in doing my math i did't take into account the fact that it was 110 and not 12v. Darn it! Oh well, thanks for your input. I guess i'll still build the panels for some lighting and cell phone charging when we go camping. Now that i pretty well know what i'm doing i can get rid of that noisy gas guzzling generator i normally use. Two years and all it has done is run rope lights and phone chargers. The setup i have planned will be more than enough for a couple led strands and cell chargers.

Thanks again! And i do feel a little better knowing that something i created won't be powering anything electrical directly. At least not in the house while i sleep anyway. Haha