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Mismatched Solar Panels- Same watts, different volts and amps

21 Comments



Hi this is Amy from the altE Store. We’ve
been doing a series of videos where we are showing wiring mismatched solar panels and what makes sense for wiring them; in series, in parallel, or just not even at all. So we’ve been putting
together a playlist, and you can see that here so you can watch through with some of
the other examples we’ve given. So right now, what I’ve got is two 100W solar panels. One
is a 24V nominal, and one is a 12V nominal. So what we are going to show is they are both
going to go through an MPPT charge controller. So going into the battery, we’re going to
measure them each individually, so we can confirm what we are getting individually.
Then we are going to wire them in series, and we’re going to wire them in parallel.
Alright? So, first we’ve got our 24V solar panel and it is going through the MPPT charge
controller, and it’s going into my 12V battery. So I’m going to turn on the solar input and
I am getting… there we go, I’ve got 32.9V into the charge controller, I’ve got 12.9V
at the battery coming out of the charge controller, and I have 5.69A going from the charge controller
into the battery. Now keep in mind, this solar panel has got an Imp, a maximum power current,
of 2.78A. So it’s putting in 2.78A into the charge controller, and it’s coming out at
5.69A. So that’s because the MPPT charge controller is taking that high voltage, it’s dropping
it down, and then it’s outputting the higher amperage with the lower voltage, retaining
most of the power. So I’m just going to write this down and then we are going to rewire
it so that we’re going to measure the 12V panel. Alright. So now I’ve got my 12V solar
panel, also 100W. So you can see I’ve got an input of about 20V, so my Vmp is right
around 18V, so it’s actually doing quite well. It’s really putting in a very high voltage, I’ve
got perfect conditions here. And it’s going through the MPPT charge controller, and it’s
outputting 4., let’s say 4.42A. So that is compared to the 5.69 amps, and it’s also right
around 13.1 volts. So the Imp of the 12V panel is 5.56A, and I’m seeing 5.81A going in. So
again, it’s doing really well. I’ve got great conditions. Because it’s dropping that voltage
down, it is actually increasing that current a little bit. So that’s one of the advantages
of using an MPPT charge controller. You can actually get a little bit better than Imp,
or maximum power current into the battery. So, I’m going to now change this around and
wire the two of them in series, and we’ll see what we get with that. Alright. So now
I’ve got these two wired in series. So I have the plus from the 12V panel going to the charge
controller. The minus going to the plus of the 24V panel. And then that minus is coming
into the charge controller. So they are wired in series. And I’m getting 43.8V going into
the charge controller, which makes sense because that’s the two of these added together, because
wiring in series increases voltage. So now coming out, I’m getting 8.81A (I’m going to
write that down, 8.81A). Because it’s taking all of the current that’s going in, and increasing
it as it’s dropping that voltage down to the 13.4V. So, now, we’re going to change it,
and we’re going to wire the two of them in parallel and see what we get for output. OK,
so I have 24V panel and the 12V panel wired in parallel. Now you see, I’ve got 23V in.
Now when I had that solar panel, the 24V solar panel by itself, it was measuring up around
40V. But because I’ve got it wired in parallel with this 12V panel, that’s putting out about
18V, it’s pulling that voltage down. So it is dramatically reducing the voltage output
of that solar panel. So just from what we see going in, we can see that it’s very unhappy
being wired in parallel with a lower voltage. So doing the series in, you saw that it had
added the two volts, and that was fine. So doing it in parallel, we’re pulling that down,
we’re greatly reducing it. The current output is about 7A, so we’ve got that lower voltage
going in, but we’re only around 7A coming out. And we were up in the upper 8 amps when
we were wired in series. So you can see here that wiring two mismatched panels, if you’ve
got mismatched voltages, and you’ve got an MPPT charge controller, wire the two of them
in series, let the voltage go through, add up, and then the charge controller, being
MPPT can take that higher voltage and reduce it down. I hope this was helpful, if so, give
us a like and a share, and be sure to subscribe to our altE Store channel, so we’ll notify
you when we’ve got more videos coming out. And don’t forget to go to our altestore.com
website, where we’ve been making renewable do able since 1999.

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21 thoughts on “Mismatched Solar Panels- Same watts, different volts and amps”

  1. Maxid1 says:

    You've given me so much useful information now, I can't figure out the solution to my situation. I think I've reached my information input limit. But I don't think I've seen my situation yet. One existing 90w 12v panel adding two 250w 12v panels in parallel. Up grading to an mppt controller and adding more batteries to the 2 that I have. Would the 90w panel drag the 250w panels down?

  2. Chris DIYer says:

    Liked/shared. Awesome explanation…numbers don't lie! Well done and GREAT conditions too.

  3. KVUSMC / Kenneth W Viar Jr says:

    Great Job Alt E

  4. ricikeri says:

    Great vids, thank you for taking the time to make them…but I'm a bit confused so I'm hoping you or some one could explain, I was given 3 solar panels, 185 watt ea…(nt-185u1) they put out on the volt meter 44.5 volts. How do I decide on Pwm or mppt solar charger? 12v or 24? Thank you…and I subscribed!

  5. altE Store says:

    Sorry Rev John, I accidentally deleted your comment. My reply to you was "Both solar panels and batteries have to obey Ohms Law, so much of their behavior is similar."

  6. Nadeem Ahmed says:

    Plz Do one Video using two charge Controllers on same Battery bank with same or separate array of solar.
    also Plz let me know is it ok to use mppt Charge Controller with PWM charge Controller with separate solar arrays but on same battery bank?? thanks

  7. waqar ayaz says:

    wow thats awesome thanks for sharing i will connect all my panels in series.

  8. Eng Mahmoud Samy says:

    great job Amy

  9. Joe Shmoe says:

    thnx for this.

  10. Richard Owens says:

    So, in this case with these panels you definitely should use separate charge controllers for each panel. Because, otherwise, you lose in either series or parallel – just more loss in parallel.

  11. Urbain Cote says:

    Because I realize that when it is very cloudy my 2 X 24V panel only provide 56-57V which is not enough to charge my batteries (I think I need 58 + V ) . Looking forward to add one 12V solar panel in serial to my actual 2 X 24 Volts on my 48V batteries setup .I actually have a MPPT controller .
    Do you think that could work and not be too much voltage for the controller during sunny day (expecting 36V + 36V + 18V = 90V) ?

  12. Salman Malik says:

    I have 4 panels 260Watts Vmp 32.16v, voc 38.10, Imp 8.08A, short circuit 8.79 A connected in series.
    and other 4 260Watts Vmp 29.99v, voc 37.89v, Imp 8.67A, short circuit 9.22A connected in series and both strings are connected parallel.
    I am using MPPT charge controller i have tested connect first string with controller and got 660watt and when connected both strings as parallel got 1050 watts and it should be 1320watts as per sum of the watts
    What i have to do to overcome the losses? Thanks.

  13. luke lewis says:

    which would work better i have 250 watt panel and 270 watt panel both mono solar panels cheers guys

    250 w – (voc 37.8) (vmpp 31.1) (imp 8.05)

    270 w – (voc 38.3) (vmpp 30.8 (imp 8.77)

  14. Escape3000 says:

    cant i match one 30vdc 230w 7.7amps with 3 17vdc 2.3amps 40w ?

  15. mario sellet says:

    Hi Amy, I have a question regarding my system. I have two solar panels connected in parallel. 1 is 5 Watts 1 is 20 watts. They are both 12 volts. I installed two diodes one for each panel. I have 2 lead acid batteries connected in parallel both of them combined equal 13 amp hours. Right now my batteries are at 12.3 volts, my charge controller is 12/24 volts and 10 amps. My problem is, when I don't connect my solar panels to the charge controller, the reading on my multimeter is 19.7 volts. And when I connect the panels to the charge controller the reading is 11.8 volts. I went ahead and used a different charge controller, by the way they are pwm. And the results were the same. I went as far as using a step up converter. And still same problem. The panels were in full direct sunlight. Can you please advise as to what the issue might be. Thanks

  16. Youbatfalcontube says:

    Hi Amy, Can you please suggest a rather cheap MPPT controller just for a 100 W panel? My needs are covered with that so I do not want an expensive gear.

  17. Luis Martinez says:

    If they have same voltage but dif watts ex. 200w / 100w

  18. zhivko ivanov says:

    Should we use a diode when conecting two different panels in paralel so tha the electricity from one can not go to the other

  19. NoVaKane says:

    The high voltage with low amp panel sounds so weird lol

  20. BOB DYLAN says:

    another very nice video

  21. The Awesome Homestead says:

    how would i do this if i have 4 of each of these? i have 4 250w 12v panels and 4 250w 24v panels.

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