3 panels 2s1p ?

DrJNC

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Jun 1, 2021
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Expensive mistake. . .new to this forum.

As my Covid project, I converted used Promaster van to a camper last summer, and we have had several short trips, and two month-long trips. Great times. My biggest knowledge deficit was electric, and this forum has provided good reassurance to my beginner efforts

However, I still made one fairly obvious mistake: I didn’t match the solar panels with my all-in-one Inverter/mppt/charger. Here’s my syste

Mpp solar PIP 2724 all-in-one. 24 volt device. Maximum open circuit voltage from panels 60v. Max charging current from panels 25A.

Lyon energy 1300 batteries x 4, 2s2p for 24v. 5280wh. (cost just under $3000 at Costco. I wasn’t quite ready for DIY, but if doing again, would probably build with 280ah cells via this forum etc.)

Microwave/induction cooker/electric kettle all run well from inverter. (not all at once. . .) 24v and 12v separate from all-in-one box also work well. (lights, water pump, elect blanket, fridge, outlets for charging devices, etc)

Rich Solar 200w panels x3. Here’s the mistake: got the 12v panels instead of 24v. When I finished install on the roof of van, (3 in series) open circuit voltage was above 60, which my 2724 correctly recognized, and shut down. Voltage for 12v in parallel too low, so I removed one panel, and we have been traveling fairly happily with 400w on the roof. However, we did come close to running out of juice several times early this spring trying to use tiny heater etc.

I did not hook up to charge from alternator. Not interested for now.

We do have shore power 15A hookup to the all-in-one box, which will charge batteries overnight, but don’t camp with hookups often.

So, I was resigned to continue with 400w on the roof, thinking that only fix would be to change all-in-one device ($600-800 depending on accessories etc), or to buy 3 new Rich Solar 24v panels. ($750).

But, just thought of another fix, for cheaper: How ‘bout buying one new 24v panel, and mounting in parallel with the two current panels? This makes the mistake only cost $240 to fix, and I think would decrease total watts from 600 to about 570?

Current 12v panels (in series): Vmp20.4v, Imp 9.8A, Voc 24.3v.

New panel 24v: Vmp 37.6v, Imp 5.3A, Voc 45.4v.

So, currently MPPT ‘sees’ 40.8v @ 9.8A. If I add 24v panel in parallel to these two, then Mppt should ‘see’ 37.6v @15.1A. This gives me 568 watts, rather than the 600 I would have had if I ordered 3 24v panels in the first place. Maybe a bit of shade tolerance too?

Math check, anyone? Sound ok? Other suggestions?
John in NC
 

NPhil

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Apr 23, 2021
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You could buy an Epever Tracer in 30A that can take 100V for less than $240, and have a backup controller. Warning: the cheaper Tracer AN controllers out there require the RS-422 connecting cable to a PC and time to scale the learning curve on their slightly flaky software to get them set right for Lithium batteries.
 

fratermus

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Mar 19, 2021
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I know you don't want alternator charging but leaving the existing panels up and adding a 20A DC-DC would cost maybe $150 after wiring costs.

If mounting a different panel I would put it on a separate controller.

the cheaper Tracer AN controllers out there require the RS-422 connecting cable to a PC

P20 of the AN-series manual (pdf) shows the AN-series being programmed by the normal MT50 remote display in addition to PC or USB/OTG.
 

NPhil

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I know you don't want alternator charging but leaving the existing panels up and adding a 20A DC-DC would cost maybe $150 after wiring costs.

If mounting a different panel I would put it on a separate controller.



P20 of the AN-series manual (pdf) shows the AN-series being programmed by the normal MT50 remote display in addition to PC or USB/OTG.
I haven't tried the MT50, what I know is I can't select lithium on the front panel of my Tracer AN 20 amp (which just died a few days after one year since purchase, BTW) or my Tracer AN 40 amp (neither of which is the most recent model, which, I gather, has a front panel option to select lithium batteries).
 

TomC4306

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Mar 2, 2021
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If space permits, I'd add one more 12v panel, 2s2p. You'll end up with your current setup just double the amps.
 

Hedges

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One 24V panel in parallel with two 12V panels works. Exact number of cells and voltage varies; it works best of Vmp of 24V panel is about twice Vmp of 12V panel. 37.6V isn't quite twice 20.4V, but close enough. If you can tilt your panels toward the sun that will be a bigger improvement that what little you lose from 7% voltage mismatch (which is probably only a couple percent power reduction.)

One more 12V for 2s2p like Tom says would be good too.

You were lucky on exceeding maximum voltage with 3s. If too much, it kills the electronics. On a cold day voltage could be higher by some 12% to 20%.
2 x 24.3V = 48.6V, still has 20% headroom to 60V limit so the new 2s configuration is completely safe anywhere you might travel.
 

DrJNC

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Jun 1, 2021
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Thanks for all responses! Next van with longer wheelbase might fit 4 panels. Sounds like my solution is not perfect, but not crazy. I'm hoping to keep it simple without new holes in roof or too much new hardware. I'm open to DC-DC charging in future.
 

HRTKD

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This problem is one reason why I'm not a fan of all-in-one units. If you're willing to add a separate MPPT device, you can keep the existing panels and have more charging.
 

sunshine

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Apr 24, 2020
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Voltage for 12v in parallel too low, so I removed one panel
If they were still on the roof you could have // the odd one out with one of the others for a slightly better wattage than just removing it.
This does work at this level for a possible increase of 19% in power output. 2S1P if this is the right designation for that config?
 
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swill4wd

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Jan 14, 2021
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How about 2 100w panels (instead of the removed 200w) in series, with the same VOC, in parallel with the 200`s?
 

fratermus

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Mar 19, 2021
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I'm hoping to keep it simple without new holes in roof
You probably already know this, but: your PM has factory-installed rack mounting studs on the roof. roof -> rack mounts -> rack -> panels.

The cable gland will require a hole to get the wiring in but other than that no solar-related holes are required.
 

Atomic Ed

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I have this same model MPP unit and also plan on using my 3 newpowa 12v 200w panels in series. I havent hooked it up yet but hoping that I won't run into the same problem as you.

The panels I have are 12v panels (will be in series): Vmp17v, Imp11.76A, Voc 20.23v

Do you think the unit will see this as too much as well and shutdown? Also I will be using a battery pack that has anderson to ring term connections and my MPP unit cam with a pre-made connector to ring term. How did you connect yours?

Thanks
 
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