PV Overload question (1200W on a Rich Solar 40A MPPT - rated for 1100W)

JMT

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Oct 6, 2020
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Hey all,

A couple of weeks ago I finally finished setting up and turning on my system with 12x 100w panels.
( thread here: https://diysolarforum.com/threads/finally-turned-on.22094/ )

It wasn't charging up my batteries as well as I expected, which I figured was probably due to the generic charge controller. At best it seemed to be producing about 800-900W.

Since the panels are all Rich Solar, I went ahead and picked up the Rich Solar 40A MPPT w/ BT. (apparently it's the same as the Renogy model)
I installed it yesterday. To my surprise, it was peaking at just over 1100W today. (the highest I saw it hit was 1135W)
Then I saw that it was triggering a "PV Overload" error each time it nudged above 1100W. My old (and apparently inefficient) MPPT was rated up to 1560W.

It's not shutting down or hurting the rest of my system, but I'm wondering if there's a likely risk of damaging the unit (or burning down my house). Documentation's hard to find (and the BT app isn't that great either).

At one point in my research I came across a random post (for the Renogy model) that mentioned it might shut down at 1.05x the rating (1155W) and need to be reset, so that's a little concerning.

If it's doing over 1100W now, I expect it'll have no problem hitting 1200W over the summer. I really didn't expect it to operate that efficiently and thought there'd be more of a loss since the MPPT is 50ft from the panels.

I'm considering sending it back and getting an EPEVER rated for 1200W instead (max 1560W).
It doesn't have the BT module, but that's not really a loss.

What do you think?

Looking forward to your feedback. Thanks!
 

JMT

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Oct 6, 2020
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How are your 12 panels wired in terms of series/parallel?
What is the Voc of your panels?
What is the max input voltage of your SCC?
What was the temperature outside when you hit the PV Overload situation?
4-series, 3-parallel for about 80v@15a
(it was originally 2-series, 6-parallel since my pv combiner box had 6 inputs, but my old charge controller wanted a minimum of 36v to charge the batteries, but whatever algorithm it used would drop it below that for higher amperage, so I combined them to switch to a higher voltage - that helped, but it still seemed inefficient)

They're the Rich Solar 100W mono panels, so about 20v/5.5a each. I'm not hitting "over-voltage" or "over-current", which are different errors, since I'm not exceeding 100V or 40Amps. It's just complaining that I'm exceeding 1100W with my 1200W array.

The temperature outside was probably about 75-80. Pretty comfortable. I'm sure that definitely contributed, but I can also easily see these continuing to perform above 1100W on a regular basis. I'm just not sure if the risks are high enough to warrant swapping the controller again for one that's rated higher, or if I'm being a little paranoid.

And it looks like that EPEVER I linked above as a potential candidate doesn't have a dedicated lithium battery setting like some of their others, so I'd want to go with a different one anyway. I thought my array was pretty small at only 1200W, but it seems like the name brand controllers often top out at 1040W while the generic brands say they'll go to 1560W for 24V systems.

So if I really need to switch the controller, I'd be happy to hear some recommendations on that also.
 

chrisski

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Aug 14, 2020
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I'm surprised about a PV overload. I thought the MPPT only pulled from the solar panels what the SCC needed, and could not overload itself.

My Victron has a max output setting. I thought all MPPTs had a max output. These are good so you don't over amp the batteries when charging, something you worry less with your lithiums than I worry with my FLAs.

So the 40 amps on your SCC also means its limited to 40 amp output. with 80 volts in at 15 amps, this comes out to 85 charging amps at 14 volts, or 42 charging amps at 24 volts. Some MPPTs say you can over-panel by 30%. If you have have a 12 volt system, your SCC is only going to be around 600 watts for 12 volts, but to get to the full 1200 watts, needs to be 24 volts. Perhaps this SCC can't be overpaneled.

I did not see it listed, but if you're showing 1135 watts on a 40 amp SCC, its got to be a 24 volt setup.
 

MisterSandals

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It sounds like you understand the situation well. I cannot see anything wrong with your setup and sounds like the 1.05x wattage max may be what you are seeing.

How about a completely different way of looking at this?
What if you spread out your charging across the day thereby maximizing your 40a (limited) charging capability. Point 4 panels east-ish, 4 panels south and 4 panels west-ish.
Your array will catch early morning sun and blend into 8 panels late morning and early afternoon on the western third.

I'd be pretty surprised if this does not increase your daily solar harvest... all with your existing equipment.
 

JMT

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Oct 6, 2020
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It sounds like you understand the situation well. I cannot see anything wrong with your setup and sounds like the 1.05x wattage max may be what you are seeing.

How about a completely different way of looking at this?
What if you spread out your charging across the day thereby maximizing your 40a (limited) charging capability. Point 4 panels east-ish, 4 panels south and 4 panels west-ish.
Your array will catch early morning sun and blend into 8 panels late morning and early afternoon on the western third.

I'd be pretty surprised if this does not increase your daily solar harvest... all with your existing equipment.
Thanks for the feedback. There's really no easy way to re-distribute the panels at this point (check my first link in the OP). There are obstacles to both the east and west (my house to the east and a forest to the west). It'd be way easier to just get a different controller.

I guess I'll let this one run for a few more days and see if it shuts down and needs to be reset (assuming it'll do that if it hits 1155W or higher). I read it on the internet so it must be true, right?

Maybe it'll prove it can survive 1200W with only a warning that can be ignored, And hopefully nothing horrible happens.
 

MisterSandals

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Another idea, sometimes I'm full of them. My wife says I'm full of something...

How about taking one panel out of each string and create a 3S array and put a cheap and cheerful Victron 75/15 (gotta have bluetooth). This will also harvest more than your 40a SCC could do alone.

So 3S3P to your existing SCC and 3S to another SCC.

If you have 3 panels that are shaded differently than the others, those would be good candidates to move to the redundant system.
 

JMT

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Oct 6, 2020
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I'm surprised about a PV overload. I thought the MPPT only pulled from the solar panels what the SCC needed, and could not overload itself.

My Victron has a max output setting. I thought all MPPTs had a max output. These are good so you don't over amp the batteries when charging, something you worry less with your lithiums than I worry with my FLAs.

So the 40 amps on your SCC also means its limited to 40 amp output. with 80 volts in at 15 amps, this comes out to 85 charging amps at 14 volts, or 42 charging amps at 24 volts. Some MPPTs say you can over-panel by 30%. If you have have a 12 volt system, your SCC is only going to be around 600 watts for 12 volts, but to get to the full 1200 watts, needs to be 24 volts. Perhaps this SCC can't be overpaneled.

I did not see it listed, but if you're showing 1135 watts on a 40 amp SCC, its got to be a 24 volt setup.
Correct. It's a 24V system. Since the charging voltage needs to be higher than the battery voltage in order to actually push power into them, the 1100W / 40A math makes sense (that equals 27.5V, whereas 1200W / 40A = 30V).
 

JMT

New Member
Joined
Oct 6, 2020
Messages
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Another idea, sometimes I'm full of them. My wife says I'm full of something...

How about taking one panel out of each string and create a 3S array and put a cheap and cheerful Victron 75/15 (gotta have bluetooth). This will also harvest more than your 40a SCC could do alone.

So 3S3P to your existing SCC and 3S to another SCC.

If you have 3 panels that are shaded differently than the others, those would be good candidates to move to the redundant system.
Yeah, that would be doable. I may try some different configurations. The old controller didn't like the lower voltage, but the new one may not have a problem with it. Thanks!
 

chrisski

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Aug 14, 2020
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Adding another SCC gives you all kinds of possibilities. Not only the Victron mentioned, but a second Renogy 40 amp could get you the option to put more energy into those batteries. You could hook 9 up to the first 40 amp SCC, and hook 3 more up to the second SCC.

The intention would be to eventually build yourself another mount for 6 more panels.

I found that when I did my calculations, I could use more solar production to get done charging earlier, and that’s why I added bank 2 on one SCC2 and bank 3 on a separate SCC3. I was getting by just fine with just one SCC, and then a cloudy day hit, and that just blindsided me. I still had enough battery to make it through one cloudy day if the sun came out the next, but I had about six cloudy days in a row. That weather in sunny AZ is a rarity.

By now you’ve had this long enough to see if this is feasible. There’s also a max charge limit. If you have 2 battleborne batteries, that limit may be 50 amps if your batteries are in parallel, but if the system is working so good, why not just add two more battleborn batteries?

Where I’m at, our powergrid is perfect, but that can’t last. It’s nice to be prepared with something.
 
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