Solar panel

Yes,

It needs a regulator. Otherwise you'll cook the battery.

You say in your post that you want to charge batteries - plural - hence more than one batery - presumably 2 batteries i.e.2 x 12 volt batteries - i.e. 24 volts requirement.

Just wire the two batteries in series for charging purposes from the solar panel = problemn solvered!

Disclaimer - I know nuttin (as Ol Sgt Schultz would say) bout lectrckery - to me it's just white fella magic, so you might wanna check my suggestion with someone who knows whatthey are doing round lectrcikery!

Cheers

Solar cells do not produce a constant output voltage. The ones most commonly used to charge 12 V batteries have an open circuit voltage of over 20 V. However they do hot produce much power at this voltage. They produce their highest power output at around 17 V. As you attempt to load them more heavily the voltage drops considerably but the current does not rise much.

Take a look at the facts. Current = power / volts. For your panel current = 5 (W) / 17 (V.) therefore the maximum current will will not be much more than 300 mA.

You measured the open circuit voltage. Now go and measure the short circuit current. If you have a meter with a current range in excess of 300 mA, set it to that range and connect the panel across the meter current terminals. If you have a meter with a 1 A scale or more you will not damage it with your panel. Others can do that with their panels. A 1 A range for panels up to 10 W, a 2 A range for up to 20 W panels and a 10 A range for most of the rest. This is a standard method of checking panels.

As your panel will only put out a very small current you will only be able to charge very small batteries. Your panel will only be able to give a maintenance charge to a decent size battery. I use a 5 W panel WITHOUT a regulator to keep the battery in my wife's Corona charged whilst we are away on our 6 months trips.

You too can use your panel, without a regulator, to keep a battery alive if you are not charging it for a few months. However forget about charging batteries with it unless you get a regulator and another dozen panels to accompany it.

PeterD

If you can include the panel's tech specs here (from the rear label), you'll get much better feedback re the query.

As PeterD says, this type of panel is for keeping a charged car battery from going flat when left for periods of time. I considered one of these four daughter's car, but opted for a jump pack as being more useful.

I don't know whether you intention was to keep a car battery topped up, or to use as a power source for a separate battery when camping. For the latter use one 80 w (at least) panel to charge one battery.

Motherhen

He doesn't need a regulator but doesn't he need a diode in the circuit to make sure the battery doesn't discharge back through the panel?