24V MPPT Solar Issues :( Slow Voltage drop due to Heat??

Hello! I'm hoping I can get some help with my low charge current issue. Please understand, this is my first solar setup/major electrical project and I've laid out the info the best I can. I'd like to be a big academic sponge to soak up any input or opinions about my situation.

I have a MPPT charge controller/inverter all-in-one (PIP 2724 LV) connected to 2-12.8V 280AH batteries in series for a 24V system. I am currently building out my van and have nearly the exact same solar setup recommended in the charge controller manual.

CHARGE CONTROLLER PV SPECS:



RECOMMENDED PANEL SETUP:



MY CURRENT PANEL SPECS:



My current panels have almost the exact same specs as recommended and it recommends 3 panels in parallel. I AM PART WAY THROUGH THE INSTALLATION AND HAVE 2 PANELS INSTALLED IN PARALLEL. I will be adding the 3rd but I strongly believe that is not part of my problem--->

PROBLEM:

Immediately after I pull the van out of a cool, shaded area and into the sun nearly directly overhead, completely clear day, 80 deg F, The charge current is ~12A which makes sense to me as 2 panels with 8.27Pmax current in parallel = 16.54A. Introduce real-world variables and 12A seems ok.

Over the next hour or so, the PV current and wattage continue to slowly decrease to 3.5-4A and 105-108W which is very far off from the theoretical 16.54A and 500W output.

After the panel reading have dropped, The charge controller is reading the panel voltage at 30V, which matches the same reading I get with the panels disconnected and measured at the controller, with a multimeter. My understanding is that the open circuit voltage SHOULD theoretically be closer to 37.6V.

CONJECTURE:

Looking at the PV voltage range of the controller (30-50V) and my panel measured voltage (30V), I am damn low, if not off the charts on the bottom end of that range. In addition, my battery voltage is 26.2V with the inverter off for no power draw, which is very close to the 30V panel voltage.

Is the voltage drop caused by the panels warming up in the sun dragging my voltage too low for the charge controller to effectively charge the batteries? Are the voltage differences between the panels and the batteries too low for a powerful charge? If so: Why the F*%# would they recommend a panel setup that would supply a voltage that is so close to the lowest recommended voltage value?

If I understand correctly, adding the 3rd panel in parallel will not affect the output voltage. If my assumption of the problem is correct, How would I fix this problem/boost the voltage? Id hate to scrap these panels.

Tomorrow I will check the panel output wattage and voltage while the panels are still cool to see if that helps me understand the issue.

Thanks for any help!

Those are 60 cell panels and are insufficient to charge a 24V battery.

Unfortunately, their recommendations are moronic. You should be using 72 cell panels, which are about 45-50Voc and about 37Vmp.

Panels are rated for 25°C CELL temperature. When the sun heats them, they easily go to ~45°C, which cuts Voltage down by about 8-10%. This is why you see decent performance when they are cool after being in the shade vs. their performance after heating up.

Well, that makes perfect sense and is very disappointing. Thank you!

Wow voltage cut by 8-10% huh. I wish they considered that when going out of their way to recommend this almost exact panel configuration in the manual.

I understand I should be using 72 cell panels instead of these but as I said earlier, Id really hate to scrap these panels. The two that are up there are mounted in a way that would be a massive pain in the butt to swap out with a differently-sized panel, let alone trying to sell 3 panels and sourcing a replacement, money doesn't grow on trees, time is limited blah blah blahhhh

That being said, Is there a safe way to boost the voltage output that reaches the controller? Will adding the 3rd-panel help at all? Is it reckless to have any other configurations using these 2 panels?
I think I remember reading that you should not use panels with different ratings together in any way.
Oddly enough, I am more partial to using a different charge controller or adding a controller/voltage booster of some kind over changing the panels. Lots of time and effort has been spent getting them up there correctly (Mounted on an 11ft box truck and I am a one-man team.)

Thanks again for input

Perhaps the easiest (note that I said EASIEST, not necessarily CHEAPEST) thing to do that would require minimal physical re-configuration of components would be to get a different AIO. The one you have has a ridiculously low input array voltage.

All you would then have to do is replace one piece of gear and wire the panels in series.

Ah yes makes me start to think about the possibility of trying to return this current gear and putting that money toward something else.

The LV2424 has better specs for PV input. It looks like it is sold out everywhere that isn't ebay strangely.

ChooChoo said:

Well, that makes perfect sense and is very disappointing. Thank you!

Wow voltage cut by 8-10% huh. I wish they considered that when going out of their way to recommend this almost exact panel configuration in the manual.

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Chinese stuff must be subjected to the sniff test by an informed consumer. Their cable gaging and fusing is often inadequate as well.

ChooChoo said:

I understand I should be using 72 cell panels instead of these but as I said earlier, Id really hate to scrap these panels. The two that are up there are mounted in a way that would be a massive pain in the butt to swap out with a differently-sized panel, let alone trying to sell 3 panels and sourcing a replacement, money doesn't grow on trees, time is limited blah blah blahhhh

That being said, Is there a safe way to boost the voltage output that reaches the controller? Will adding the 3rd-panel help at all? Is it reckless to have any other configurations using these 2 panels?

Click to expand...

No viable boost method.

The third panel will improve existing performance by about 50% as you've added 50% more PV.

2S would likely damage the MPPT.

ChooChoo said:

I think I remember reading that you should not use panels with different ratings together in any way.

Click to expand...

Not correct. Two considerations:

1) Vmp should be within 5-10% when in parallel.
2) When in series, all panels will operate at the current of the lowest current panel.

ChooChoo said:

Oddly enough, I am more partial to using a different charge controller or adding a controller/voltage booster of some kind over changing the panels. Lots of time and effort has been spent getting them up there correctly (Mounted on an 11ft box truck and I am a one-man team.)

Click to expand...

A 30A charge controller capable of accepting 150Voc input would work with those three panels in parallel. EDIT: no!!!! I meant series!!!!

I have this unit and don't experience this problem. While my overall amperage I get from my 2 x 220w solar panels basically maxes at 12amps, it charges perfectly. I use a 52voc panel, but they are older. I've measured it in multiple conditions and. have never seen over 48voc.
Point being, the lv2724 has the most anemic charge controller of any 24v Aio. That's its downfall, that would otherwise be a perfect unit. And that being said, you have to be strategic with your panel selection.

For reference, I am using some old Sanyo Panasonic HIT-N220A01 (72 cells) panels with this unit.

You happen to have one of the worse AIO's when it comes to charging unfortunately. A Growatt 3000TL-LVM or the MPP 3024 will both handle a LOT more solar. It's a pretty stiff price premium to have those outlets mounted on the unit. I have the Growatt at my camp and while the upper limit on voltage is only 145, it starts charging at a low enough level that a single 40v panel works just fine. A lot of the other ones require stupid voltages (150v+) to charge a 24v battery.

The lv2724 has come down in price since I purchased mine.
US warehouse

I would use the 3024lv-msd if I were doing a similar build again. The lv2724 is approx the same weight as the 3024, but the 2724 does have the benefit of being quite a bit smaller dimensionally.

Edit: I actually may not have changed it. For the hand truck, this thing is nearly perfect, size, power, and outlets are an added benefit.

BuffaloTrace said:

Point being, the lv2724 has the most anemic charge controller of any 24v Aio. That's its downfall, that would otherwise be a perfect unit.

Click to expand...

Rednecktek said:

You happen to have one of the worse AIO's when it comes to charging unfortunately.

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Ouch! The truth hurts. At least this is a great learning experience.

sunshine_eggo said:

Not correct. Two considerations:

1) Vmp should be within 5-10% when in parallel.
2) When in series, all panels will operate at the current of the lowest current panel.

A 30A charge controller capable of accepting 150Voc input would work with those three panels in parallel. EDIT: no!!!! I meant series!!!!

Click to expand...

Thank you for the info on panel combos. I'll keep this in mind for future projects! Sounds like a different charge controller is a more newbie-friendly approach to my current situation.

I've looked into 3 different AIOs based on your recommendations and a bit more research. MPP 3024LV-MSD, Growatt 3000TL-LVM, MPP LV2424 in order of ascending price. All of their PV ranges would require my 3 panels to be in series ending up at: 90.9Vmp, 8.27Imp.

The 3024 has a PV range of 90-230V and a "Startup" Voltage of ~80V. That is not confidence-inspiring at all given my voltage would still be scraping the bottom of the voltage range requirement. Idk what that 80-90V difference is. Maybe that is them taking voltage drop into account but it makes me uneasy.

The 3000 has a 30-115V Range which would be perfect for the 90V panel setup. Is the 115V Max enough for a voltage spike in the winter? They are used panels so maybe that is less of a worry. The 3000TL has an 80A charge current limit. Seeing my current would be 8.27A, Is there a bottom end of the range or is that just for voltage?

The 2424 has the same 30-115V charging range, same 80A charge limit but 600W less AC output and more expensive.

I'm leaning toward the Growatt 3000TL.

Any opinions? Different AIO recommendations? Should I ditch the AIOs and go on a research journey of piecing together a separate charge controller and inverter setup?

That 31 volt panel can only work on a pwm controller for a 24 volt battery.

A mppt need 5 volt differences from the battery volts.
A pwm controller not ,on the moment a small volt is higher than the battery it will start charging .

So yes you can use it to charge but than you need a pwm controller .
You do need a pwm controller that you can set your self the volt for a lifepo4 battery .
Victron and epever are the only one that have it.

Personal note.
Just use a external mmpt controller dat can handel the extra volts .
Or a cheap pwm controller that you can Program.
Again i will go for new panels and sell the old ones

ChooChoo said:

Thank you for the info on panel combos. I'll keep this in mind for future projects! Sounds like a different charge controller is a more newbie-friendly approach to my current situation.

Click to expand...

Please note that I did not mean to indicate the three panels in parallel but in series. Edited the post you quoted.

ChooChoo said:

I've looked into 3 different AIOs based on your recommendations and a bit more research. MPP 3024LV-MSD, Growatt 3000TL-LVM, MPP LV2424 in order of ascending price. All of their PV ranges would require my 3 panels to be in series ending up at: 90.9Vmp, 8.27Imp.

Click to expand...

You need to find an AiO with a ~145-150Voc limit.

ChooChoo said:

The 3024 has a PV range of 90-230V and a "Startup" Voltage of ~80V. That is not confidence-inspiring at all given my voltage would still be scraping the bottom of the voltage range requirement. Idk what that 80-90V difference is. Maybe that is them taking voltage drop into account but it makes me uneasy.

Click to expand...

Nope.

ChooChoo said:

The 3000 has a 30-115V Range which would be perfect for the 90V panel setup. Is the 115V Max enough for a voltage spike in the winter? They are used panels so maybe that is less of a worry. The 3000TL has an 80A charge current limit. Seeing my current would be 8.27A, Is there a bottom end of the range or is that just for voltage?

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This one. The 80A is the OUTPUT limit to battery. Not relevant to PV input current. 8.27A is fine.

ChooChoo said:

I'm leaning toward the Growatt 3000TL.

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Yep.

Or... a single 150V MPPT for the 3 panels you have in SERIES on top of what you already have.

The epever itracer-nd or old model tracer-nd
Those have a 150volt input and are cheaper than a victron 150volt serie.

sunshine_eggo said:

This one. The 80A is the OUTPUT limit to battery. Not relevant to PV input current. 8.27A is fine.

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Ahhhh I see. Thank you for the clarification.

sunshine_eggo said:

Yep.

Or... a single 150V MPPT for the 3 panels you have in SERIES on top of what you already have.

Click to expand...

Ok this is great.

If I can return my unit (which I doubt I'll be able to, though I have heard good things about customer service at watts247 where I purchased my unit), I'll get the Growatt 3000TL.

If I can't, I'll use a 150V MPPT with my panels in series to take advantage of my current setup. My current AIO can still act as an inverter, utility charge controller and leaves the possibility to expand my panel setup in the future with consideration of what power my batteries can take.

Does that sound about right?

I really really appreciate all the input on my situation!

ChooChoo said:

Ahhhh I see. Thank you for the clarification.

Ok this is great.

If I can return my unit (which I doubt I'll be able to, though I have heard good things about customer service at watts247 where I purchased my unit), I'll get the Growatt 3000TL.

If I can't, I'll use a 150V MPPT with my panels in series to take advantage of my current setup. My current AIO can still act as an inverter, utility charge controller and leaves the possibility to expand my panel setup in the future with consideration of what power my batteries can take.

Does that sound about right?

I really really appreciate all the input on my situation!

Click to expand...

Well yes.

What you can do with the old aio mppt .
Make a connector outside .
So you can set solar panels out side if you stay long time on one space
Just thake solar panels set some hinges on it like suitcase.

ChooChoo said:

Ahhhh I see. Thank you for the clarification.

Ok this is great.

If I can return my unit (which I doubt I'll be able to, though I have heard good things about customer service at watts247 where I purchased my unit), I'll get the Growatt 3000TL.

Click to expand...

Ian with Watts247 has a good repuation.

ChooChoo said:

If I can't, I'll use a 150V MPPT with my panels in series to take advantage of my current setup. My current AIO can still act as an inverter, utility charge controller and leaves the possibility to expand my panel setup in the future with consideration of what power my batteries can take.
Does that sound about right?

Click to expand...

Yes. You could get two lightweight flexible 100W panels and deploy them 2S for additional power.

ChooChoo said:

Ahhhh I see. Thank you for the clarification.

Ok this is great.

If I can return my unit (which I doubt I'll be able to, though I have heard good things about customer service at watts247 where I purchased my unit), I'll get the Growatt 3000TL.

If I can't, I'll use a 150V MPPT with my panels in series to take advantage of my current setup. My current AIO can still act as an inverter, utility charge controller and leaves the possibility to expand my panel setup in the future with consideration of what power my batteries can take.

Does that sound about right?

I really really appreciate all the input on my situation!

Click to expand...

If I can get a 3rd sanyo panel I'll use that, but that charge controller should be able to handle 4 x 200w panels wired in 2s2p, especially they are not arranged optimally. Something like the "12v" style panels with 22voc+
4 of these would be an optimal setup for the lv2724's charge controller.

25a of charging is nothing to sneeze at even for a 280ah battery. But a couple higher voltage 400w 72/144 (split) cell panels would be cheapest.

ChooChoo said:

If I can return my unit (which I doubt I'll be able to, though I have heard good things about customer service at watts247 where I purchased my unit), I'll get the Growatt 3000TL.

Click to expand...

Ian's got a good rep on here, and I'm sure he'll be able to help, especially if you're going to get the Growatt from him. At that point it's just shipping and paying any difference.

As to the unit, I have one up at my camp. At the time I bought it the only other 24v AIO options were the LV2424 for $200 more and a super sketchy Eco-Worthy. It's worked so well I have another one in a box waiting for my next camp trip to power my laundry room. The low voltage requirement and high amperage were a significant bonus for me too.