I've got an existing 12v solar array with 1x 130 Watt and 2x 80 Watt for a total of 290 watts @ 12v, fed to a 30 amp MPPT controller (Rogue MPT-3024). I bought what I thought was going to be a 200 watt 12v panel to bring me to a total of 490 watts, which is the limit for that controller. However, the panel they shipped me is a 250 watt 24v panel. Before I go back to them to request they swap it, is there any advantage in keeping it, and using it with the 2 x 80 watt panels wired in series? This would give me 320 watts at 24V, this is where I get confused - does that give me the equivalent of 640 watts @ 12v? The controller can either 12v or 24, I think it caps out at 418 watts @ 24v to a 12v battery bank.If I really get 640 watts to the battery, I can take the unused 130v panel and give it to my dad.Thanks

If the controller handles 24v and no higher, then you'd have to run the new panel in parallel with the 2-80s (hooked in series.) Then you have a 250w panel in parallel with a "160w panel" giving you 410w. I'm not sure how you arrived at 320w. That's a big imbalance, but in parallel it just may work. I'd be willing to give it a go and see what happens. If your controller can handle more than 24v, it won't help at all because you definitely will have problems putting your new panel and the 80s in series for 48vdc. The amperage in that circuit would be severely restricted by the smaller panels. Imbalances are a big deal with series wiring.410 watts @ 24v = 17a, which theoretically pumps 34a into a 12v battery bank.phemens wrote:.. 320 watts at 24V, this is where I get confused - does that give me the equivalent of 640 watts @ 12v?No, watts stay the same (they're conserved). 320w@ 24v= 13.3a, which is 26.6amps for a 12v system. 12v * 26.6 = 320 watts.

It would actually be 130 in parallel with two 80s in series, parallel with the new 250 for a total of 540 watts.Not sure how well the power point tracking will work with the variety of panels.On edit, that won't work either because the single 130 will still be 12-volt. If you want to use the new 250 you can't use the 130. You could probably parallel everything but then you would only get half power from the 24-volt panel for a total of 415 watts (410 without the 130). I'd send it back, but shipping is a killer.

It's like taking an essay test, isn't it?

Watts are watts. Changing the voltage doesn't change the watts.I don't think you'll find a 200 watt 12 volt panel. The largest 12v panel I've ever seen was 140 watts or so.You could always add a second charge controller just for the 24v panel. Connect it in parallel with your current set up and everything will work fine.Otherwise, there is no way to use all of your current panels with your current controller.

phemens wrote:I've got an existing 12v solar array with 1x 130 Watt and 2x 80 Watt for a total of 290 watts @ 12v, fed to a 30 amp MPPT controller (Rogue MPT-3024). I bought what I thought was going to be a 200 watt 12v panel to bring me to a total of 490 watts, which is the limit for that controller. However, the panel they shipped me is a 250 watt 24v panel. Before I go back to them to request they swap it, is there any advantage in keeping it, and using it with the 2 x 80 watt panels wired in series? This would give me 320 watts at 24V, this is where I get confused - does that give me the equivalent of 640 watts @ 12v? The controller can either 12v or 24, I think it caps out at 418 watts @ 24v to a 12v battery bank.If I really get 640 watts to the battery, I can take the unused 130v panel and give it to my dad.ThanksI would advise you to "look into miss matching panels with a MPPT controller" Do your homework. If you do not your charge controller may end up being less efficient then a PWM controller.Good luck with your project!

Little confused, 12v vs. 24v solar | Good Sam Community

phemens
Explorer
Oct 21, 2015
Ok, I think (!) I'm less confused than when I started ;) Thanks for all the opinions. The 250w 24v panel will feed the Rogue controller, I'll feed the 130w and 2x 80w 12v panels to a new Solar30, all is good.
JiminDenver
Explorer II
Oct 19, 2015
Search my post for the miss matched panel test. The controller certainly does get confuse, never able to settle on a voltage. Matched panels of Voc, amps AND type produce the best results.
2oldman
Explorer II
Oct 18, 2015
OP.. more confused?
BFL13
Explorer II
Oct 18, 2015
First note the voltage limit of the controller, which is the total Voc (not their Vmps!!) before choosing to put them in series at all.
grizzzman
Explorer
Oct 18, 2015
brulaz wrote:
MrWizard wrote:

...
its about matching panel voltage when parallel
series panels must be identical "AMPS" so identical panels are used
parallel panels need matching "voltage for the MPPT parallel circuit input to work correctly
...

Been wondering about this. Some questions:

1) I know you want to match parallel panel voltage for best MPPT controller operation, but does it matter as much or at all for PWM?

2) For panels in series, you match amps otherwise the panel with the lowest amps (highest resistance?) limits the total current output? Or ...?

3) And that limitation for panels in series (2 above) is independent of whether you have a MPPT or PWM controller?

#1 12 volt panels are in the 17 to 18 volt range wont affect much.

#2 you need to match volts. If you use different amps the larger amp panel will only produce what the lower amp panel does.

#3 I am unsure of what you are asking but mismatch is much less of a issue with PWM.
FlatBroke
Explorer II
Oct 18, 2015
I hardly understood any of this. But I hate mix matching stuff. Just adds to my confusion.
brulaz
Explorer
Oct 18, 2015
MrWizard wrote:

...
its about matching panel voltage when parallel
series panels must be identical "AMPS" so identical panels are used
parallel panels need matching "voltage for the MPPT parallel circuit input to work correctly
...

Been wondering about this. Some questions:

1) I know you want to match parallel panel voltage for best MPPT controller operation, but does it matter as much or at all for PWM?

2) For panels in series, you match amps otherwise the panel with the lowest amps (highest resistance?) limits the total current output? Or ...?

3) And that limitation for panels in series (2 above) is independent of whether you have a MPPT or PWM controller?
12thgenusa
Explorer
Oct 18, 2015
The controller won't be confused. It will just choose a voltage that returns the highest power from the panels as a group. However that voltage will most likely not be the optimal voltage for any individual panel.
JiminDenver
Explorer II
Oct 18, 2015
Running mismatched panels will result in the lowest panel affecting the rest in both parallel and series.

It can also leave you with a confused controller.

I have seen larger 12v panels up to 300w, and smaller high voltage panels like the 140w 48v panels SolarBlvd.com has now.
CJW8
Explorer
Oct 18, 2015
Consider getting another identical 250 watt panel and put 500 watts on your Rogue. You are in Canada and your panels are probably flat mounted so the rogue is never going to see 500 watts. Sell or give to your dad the other panels.

I am currently running 2-250 watt flat mounted panels on my Rogue MPT3024 with no issues.

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