Why when I splice together TWO small solar panels, that the volts & amperage drops instead of doubling? But its higher with just 1 alone....?

Why when I splice together two small solar panels, they volts and amperage drops instead of doubling? But is higher with 1 alone?

I am new to solar panels, and im trying to learn more about them. I have two small panels you would use on a house motion led light, their not very powerful by any means.

With reading one, on my multimeter it shows on a sunny day about 10-11volts with the amps at 0.02-0.03. Very small I know, milliwatts power.

But when I put the other one in series with the first one, sunny day volts drops to about 5 and amps output drops to 0.01 and stays there. I'm confused why im not seeing like 20 volts and 0.05 amps at least.

Sorry for sounding like a complete noob, I am planning on putting this on the roof of my truck to keep the battery a constant trickle charge when parked in the sun.

3 Answers

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  • 8 months ago

    If you want higher voltage, then put them in series as the other answers indicate.  If you want more current (with the same voltage a 1 panel) then connect them in parallel - red to red and black to black. 

  • 8 months ago

    Joining mistake,as you joined them in series, must follow their polarity, like + - + - and so on. In series, voltage increases close to double but ampere maintains the same like in one.

    Correct your mistake by reversing one wire then join again.Use a DC voltmeter to determine its polarity if the panel terminals without marking + or - .

  • 8 months ago

    you probably connected them incorrectly. They are polarized, and must be connected in series with + to –

    see below. Connections are in red.

    for car battery charging, you need at least 15 volts, and you need to add a diode to prevent the solar pianels from discharging the battery when dark.  shown 

    PS, you can put the diode between the two panels, might be easier.

    Attachment image
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