Solar panel output

[eraser]

I know if i put two 12volt 80 watt panels together in series the output will be 24 volts at 80 watts , But what happens if you put two differant panels together in series , such as an 80 watt panel and a 10 watt panel ,the voltage would be 24volts?

what would the watt output be?

[richhagen]

If you put two 12 volt 80 watt panels together, the output will be 160 watts in full sun.  

I don't claim to be an expert on all of this, but I'll explain as best I can:

First the units:

Amp; An amp is a unit of current, which means basically how many electrons are passing a given point, or more precisely, how much charge is passing a given point measured in Coulumbs per second, where a Coulumb is a specific quantity of charge, in the case of electric current, 6.241506×10^18 electrons (which is an incredibly huge number)

Volt; A measure of electrical potential or electromotive force based upon a charge differential between two points.

The Watt is a unit of power, that is to say that it is a rate of energy usage.  It is defined as one Joule per second. Conveniently enough, if you multiply the current in Amps by the Voltage in Volts, you get the power in Watts.

Now, back to your panels.  When you connect two panels, or batteries for that matter, in series, at maximum power, the current will remain the same, but the voltages will add.  

Say your panel put out 1 Amp of current at 16 Volts at its maximum power point.  This would be an output power of 16 Watts.  If you took two panels and connected them in series, at the maximum power point, they would still put out one amp, however the voltage would be at 32 volts.  The power would then be 1 Amp multiplied by 32 Volts, or 32 Watts.  

Now, if we connected the same two panels in parallel, the currents would add and the voltage would remain the same.  The voltage would be 16 Volts, and the current would be 2 Amps.  The power would then be 2 Amps * 16 Volts, or 32 Watts.

For a real system, the way you connect the panels is going to depend upon the type of panels, charge controller, and the voltage of the battery bank you have.  If you had a 12 volt battery bank and the same two panels used as an example above, and you were to connect them in series through a shunting type of controller, you would get about one amp of charging to the battery as the battery bank would pull down the voltage and for solar panels to match that of the batteries at around 12 volts. The current does not generally go up appreciably.  If you were to connect them in parallel, you would get about two amps current into the batteries at 12 volts.  

Now for your last question, if you were to hook two different panels up in series together, what would happen.  Think of a plumbing system.  The current would be analogous to the flow rate of the water, the voltage would be analogous to the pressure.  if you have a section of 1/4" pipe  connected on the end of a 2" pipe, the effect on the flow rate is going to be dominated by the 1/4" pipe.  Well, for the solar panels, the panel with the lower current rating will only allow so much current to go through.  You will get your 24 volts, but only at approximately the current rating of the smallest panel.  About .83 Amps into your batteries in your case with the 10 watt panel limiting the current.  

Hope this helps some, maybe someone can explain it a little better that I.  Rich Hagen

[drdongle]

Or in other words your output will be limited by the capacity of the smaller of the two panels.

[scottsAI]

Very good, one more point.

Lets say you have 10 1.2 volt cells. Rechargeable.

All connected in series. For a 12 volt battery.

You put a 1 ohm load on it. Current is 12 amps.

When you last charged the batteries you forgot one.

What's going to happen?

The other cells are will continue to output, but the one cell will become dead as in zero volts, battery output drops to 10.8 volts. But if we continue discharging the battery the dead cells voltage will become reversed, usually will stop at 1.2v, Now the battery packs voltage is 9.6v. This is a bad thing to have occur. The reversed cell can be destroyed or suffer internal damage. Normally the other cells in a battery are nearly exhausted so they do not due much damage.

When your using a cordless tool this happens when the battery pack is nearly exhausted. If the tools speed drops suddenly stop and charge it. Running it for the next couple minutes will be damaging to the cell that discharged first.

Solar panels have reverse blocking diodes in them. The diodes are needed or the output of the array could drop if one cell goes bad, Shadow across the panel etc.  

In your example, the higher wattage panel will continue to output, may reverse the voltage across the smaller one. If no diodes present no output. Not good to reverse the voltage across a solar cell.

Have fun.