Proper voltage and amps to battery without a charge controller

[Kebast]

For sure!

Red-Green sez you need more duct tape, not masking tape

[ATTACH=CONFIG]2028[/ATTACH]

Haha, I most certainly agree! Sadly, I just moved into a new house and have already used all the duct tape

bcroe,
I put a large heat sink on the LM317. It did get hot fairly quick. This panel probably pushes too much current for that simple circuit. From memory, the panel is 19.1 volts, 2.7 amps open circuit (I stated 1 amp incorrectly in an earlier post). All this is mostly just proof of concept. Also, I have little to no experience in building circuits, so I wanted to start with something simple before putting together a switching controller.

[Kebast]

Update

So my little project is still going strong. My homemade solar panel and linear DC controller has been happily charging a 10 ah battery that I've been using to charge cell phones and the like. I have found a couple of problems. Since the solar cells have no encapsulant, some have cracked from heating and cooling. That hasn't really affected the output though.
My next project is to make a switching controller using info from http://www.mdpub.com/555Controller/

Then I'll try my hand at making a more durable panel .

[PNjunction]

Neat. For a real small project I have, I used three of Radio Shack's newer tiny panels (6v, 1.5watt) in series. They come in a range from 0.5 to 1.5 watt and a variety of voltages 4.5/6/9 volts and amazingly are hanging on racks. Might be an option for those that want to string together some already encapsulated dinky panels. These seem to be a bit better in quality than the project-kit types seen in the past.

Definitely not the best deal $$/watt wise..

[inetdog]

... so that the panel would produce usable voltage for more hours.

Thanks for the help!

A solar panel getting less than the maximum incident light will not deliver a (much) lower voltage. It will deliver less current.
As long as the panel voltage is high at Imp to charge the battery properly, the best use of cells is to put more in parallel to deliver more current.
The alternative is to use an MPPT charge controller which will convert the "wasted" voltage into more current.

[Kebast]

Yep

A solar panel getting less than the maximum incident light will not deliver a (much) lower voltage. It will deliver less current.
As long as the panel voltage is high at Imp to charge the battery properly, the best use of cells is to put more in parallel to deliver more current.
The alternative is to use an MPPT charge controller which will convert the "wasted" voltage into more current.

Yes. I learned quite a lot putting this project together. With anything other than direct sunlight the current drops off quite a bit. Even heavy cloud cover still produces 18-19 volts, but current drops to about 10%.

PNjunction, I've looked at those panels from radio shack. They are too expensive to really do anything with. Could make a portable cell phone charger or something, but the cost would be a bit steep.

[PNjunction]

Yes. I learned quite a lot putting this project together. With anything other than direct sunlight the current drops off quite a bit. Even heavy cloud cover still produces 18-19 volts, but current drops to about 10%.

Yep - the 10% point for me is when there is just enough sun to start making a shadow, most noticeable first with barely detectable shadows from sharp edges. If I can't obtain even an edge-shadow outline, I pack it all in.

PNjunction, I've looked at those panels from radio shack. They are too expensive to really do anything with.

Most definitely - nobody in their right mind would contemplate making a big array out of them. I'll bet there is a video out there somewhere with two or three of these micro-panels attached to a 100ah starting battery and a 750 watt inverter.