# How to limit voltage input

#### mattc2

Joined Mar 14, 2010
9
Hi,

I'm currently doing a school project and trying to feed the power from the solar panel to household electronics. So I have my solar panel generating power, feeding that into an inverter to convert from DC to AC power. However, the inverter can only take up to 12v, and the solar panel can generate up to 21v under ideal conditions... which is too much for the inverter...

How do I ensure that the voltage feeding into the inverter is limited to a max of 12v?

Thank you

#### Dx3

Joined Jun 19, 2010
87
How much current can the solar panels provide?

#### mattc2

Joined Mar 14, 2010
9
On the specification the rated current is 8A, and when I put it under sun light, the measured short circuit was something like 20mA

#### Norfindel

Joined Mar 6, 2008
326
Did you buy the inverter for this project? It seems to me like you need to use one intended for that solar panel.

#### mattc2

Joined Mar 14, 2010
9
Yes I did. The inverter can only take up to 12V DC, thats why I want to find out a way to limit the voltage

#### Norfindel

Joined Mar 6, 2008
326
I would go to the place where you buyed it, and ask for advice. If the inverter were intended to be used with that panel, i suppose it would have a wider input voltage.
You could put another DC-DC converter in the middle, but every stage losses power, and it's not a good idea.

#### retched

Joined Dec 5, 2009
5,208
You do not want to lose half of your power. Getting a proper inverter will make you project all that much more of a success.

I would be worried about only getting 20ma when you should be getting 8A.

It may be the method of metering, but you should check for sure.

#### mattc2

Joined Mar 14, 2010
9
Thanks guy for all the help.

To clarify, my prof told us to get the inverter first - so then we ordered one online with a max input voltage of 12v (for \$150). Then he found a solar panel from a random lab for us to use. So I guess our only option left is to work with what we have... maybe just use the DC to DC converter?

#### mattc2

Joined Mar 14, 2010
9
Hmmm where would I find these variable DC to DC converters? Most the ones online are either AC to 12v DC, or 110V to 12V DC... but my solar panel's DC output will be variable depending on the lighting condition

#### Norfindel

Joined Mar 6, 2008
326
I'm no expert in solar energy, but isn't the solar panel supposed to charge a battery and power the inverter?

It seems to me like you need a solar-powered battery charger, and then connect the battery to the inverter. The voltage of a fully charged battery is close to 14 volts, but the inverter should be able to handle it, if it's meant to be used with a battery.

It will be less efficient than connecting the panel to the inverter directly, if it could be done, but i bet this is how it's normally used, and your load doesn't turns-off immediatly when a cloud hides the sun.

Educypedia has a page on solar-powered circuits: http://www.educypedia.be/electronics/circuitssolar.htm or you can go with a commercial solution.

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