PV connection questions

[bodyguy]

Is it possible to connect two panels of different size together in series?

my two panels are a 60 watt 12 volt and a 120 watt 12 volt.

Thanks for any help.

Craig

[Opera House]

Yes, but you would be limited to the max current of the lowest panel in series.

[mettleramiel]

Yes, you can connect them in series, however, while you will increase the voltage to 24, you will only get the amperage of the lowest panel. Meaning that that you will get 60w at 24v. If you connect in parallel, though, you'll get 180w at 12v. Even with the lower efficiency of 12v, you would get much more out of them.

[bodyguy]

Thank you. I was worried about over powering the smaller panel and destroying it.

I just switched my turbine over to 24 volts and was hoping to be able to have them both use the same bank of batteries. It sounds like I still can but will be wasting alot of energy.

Thanks again.

[bodyguy]

Thank you. I was worried about over powering the smaller panel and destroying it.

I just switched my turbine over to 24 volts and was hoping to be able to have them both use the same bank of batteries. It sounds like I still can but will be wasting alot of energy.

Thanks again.

[rossw]

you will only get the amperage of the lowest panel. Meaning that that you will get 60w at 24v.

Bzzt. You got the first part right, then blew it with the second.

Your 60W panel will deliver roughly 5A @ 12V (60W), so the two in series will be limited to that. At 24V, thats TWO panels giving 60W each = 120W @ 24V (still 5A)

[mettleramiel]

Oops! Guess I should read over my post a little better before I hit submit!

[bodyguy]

Thank you. I was worried about over powering the smaller panel and destroying it.

I just switched my turbine over to 24 volts and was hoping to be able to have them both use the same bank of batteries. It sounds like I still can but will be wasting alot of energy.

Thanks again.

[rossw]

Depends. If you have a theoretical 180 watts (60+120) but you only get 120 from them, you're down 1/3 (33%). If your nett gains from other things account for more than that (and I don't only mean lower losses in your wiring), then you may not actually be losing as much as you think.

Even more so - the 60W and 120W will be the absolute maximum you can get from the panels under normal conditions, the reality is that a nominal 12V/60W panel will likely deliver that 60W at 17.5V - about 3.4 amps. If your battery was at 12.5 volts, you'd only actually get 43 watts from your panel. (86 from your 120W), so unless you have a MPPT charger, you're probably down from (43+86=129) to (43+43=86)

Even worse, if you have less than ideal sun, or elevated temperatures, your panels output may be less again.

You are probably only "wasting" 40 watts or less, and may well make that up in small gains in the rest of the system by going to 24V.

(Of course, you could sell the small panel and get another 120W, or just get another 60W panel - you'll get more than just 60W additional benefit from it!)

(Grrr... 4 times trying to post this reply)

[Junkie]

Is it possible the smaller panel could overheat due to the larger panel trying to push too many amps through the system ?