Epever Over Paneling; how much is too much?

[12VoltInstalls]

Setting the stage
I have intentionally bought too many watts of panels not because I need the watts- but rather because I wish to have enough voltage to create usable charging in poor sun /overcast conditions.

Overcast conditions are a consistent problem here in the Northeast Kingdom of Vermont Nov to January and Feb through March or later where we can go for weeks without any blue skies or seeing the sun - especially Nov and December.

Backdrop
I have read a number of threads and the opinions are all over the place in regards to how much one can over-panel an SCC- specifically the Epever units. If one divides the max panel figures from some of Epever’s literature by the max charge, one would surmise that one could roughly overpanel to 135% of charging max wattage.
The below quote is in regards to a 100VOC models (I have two new-in-box Triron 4215AN units) but the principal is the same:

Actually when you read the Epever Tracer AN manual very closely you will see that the figure "1.5x" the maximum charging power is given as a "suggestion" as they do not wish for you to waste money on excessive over-paneling. I interperate this paragraph as that there is NO specific maximum per se, as long as one stays under 100v.

So one could conclude that unlimited panel wattage is acceptable as long as one does not crowd the VOC max.

The greater the voltage, the lower the efficiency. However, the reduced wiring losses often offset this.

Ultimate conversion efficiency is not my goal, here.
Producing usable charging in suboptimal conditions is my goal.
While I’m aiming for a practical result with purpose, there is a secondary motivation of fun; an experimentation for entertainment value. However I am off-grid so things do have to work.

Specifications
I have six “NOS” new panels:

REC Solar	72 Series
Model Number	REC315PE72
STC Rating	315.0
PTC Rating	288.4
Open Circuit Voltage (V)	45.5
Short Circuit Current (A)	9.09

I have two 4215AN SCCs.

• Model: Triron4215N
• Rated charge current: 40 Amp
• Nominal system voltage:12V/24V DC
• Max. PV input power: 520W charge for 12V battery system / 1040W charge for 24V battery system
• Max. PV open circuit voltage:150V(at minimum operating environment temperature) ;138V(at 25℃ environment temperature)
• Grounding : Common negative
• Battery input voltage range : 8～32V
• MPP voltage range:V(BAT+2V)～72V
• Tracking efficiency : ≥99.5% , Max. conversion efficiency :98%

(I initially wanted an 8420AN for 3S2P but they went out of stock everywhere except the rapist on ebay. So I bought the two 4215s)

Some are going to ask about batteries and inverter. These are not relevant to the question because they will do what I need. But here it is:
I may add a third for capacity but I bought two cheapo/risky btrpower 140Ah LiFePo 12V ‘replacement batteries’ for this new system (because LiFePo doesn’t care if they are partly charged for a week or two, and they will basically take all of whatever 12.8VDC nominal I feed them) along with 125A Class T fuses for each battery.
The inverter I’m using is a QZRELB (aka Reliable) 2000W pure sine because it has quite low idle consumption; is well under my wiring ampacity; runs the coffeemaker, refrigerator and iron; and will start and run my smaller portable tablesaw.

So the above Epever published specs indicate a max watts of charge as 520W for a 12V system for the 4215AN. One 2S string exceeds that slightly and I’m sure that’s not an over-panel issue.
However, what about 2S2P? Or even 3S3P?!
If I use one controller at 2S: 630W and the other at 2S2P: 1260W; will that theoretical 1260W be “too much?” As best as I can tell it should be fine, and I do not care in the slightest about how many full-sun watts I “leave on the table.” This is about poor-weather charging not about maxing out my harvest. I already have plenty of power in the existing 800W FLA system during summer and sunny winter weather.

It seems it should work- it’s well under VOC and if it won’t pass >40A at nominal 12VDC the panels will not put out what they don’t see for a load, right? Or wrong?

But will a 4215AN just simply not pass the “extra” ~700W? Or fry?

How much is too much- and why?​

There is a Part B but that isn’t relevant now as part A is not yet solved and I don’t want to add that separate independent discussion.

Thank you for your time. Hoping @chrisski and @Hedges and the other 4 or 5 usual enginerding suspects stop in.

 

[sunshine_eggo]

Basis: Victron is very liberal in their over-panel limits. Don't exceed Voc or PV input current limits, and you can over-panel to your hearts content. They also publish the PV input current limit, which few others do. When one digs deeper into this limit, even Victron folks say that the input current limit is flexible in normal operation. It exists primarily to ensure that the PV reverse polarity protection will function. If your array exceeds the PV input current limit and you connect your panels polarity-reversed, you may pop the controller.

When PV input current limit is not publish, it is presumed to be equal to the output current limit. In this case, 40A.

Trying to optimize Vmp with 6S 12V panels, that should put you around 108Vmp.

108 * 40 = 4,320W max theoretical with something like 6S4P of 180W 12V panels, but you're likely riding the Voc limit a little close here at 132V.

In your case, 72 cell panels will be about 80Vmp at 2S and 4P is under the 40A limit, so a 2S4P array would seem workable at 2,520W.

With each string facing different directions, you could drive that higher.

 

[12VoltInstalls]

In your case, 72 cell panels will be about 80Vmp at 2S and 4P is under the 40A limit, so a 2S4P array would seem workable at 2,520W.

Thank you.

You approached that from a slightly different angle than others. One thing you said,

Don't exceed Voc or PV input current limits, and you can over-panel to your hearts content

Soooo… I’m reading that and my head is saying, “but the SCC limits the amps” but I think you mean if I- for example- did 2S4P that would yield (nominal) 32A then I would be almost past the thin ice and falling into open water. Correct?

In your case, 72 cell panels will be about 80Vmp at 2S and 4P is under the 40A limit, so a 2S4P array would seem workable at 2,520W.

So with one controller I would/could be ~32A 2S4P but unfortunately I bought the last six panels- I wanted eight.

With each string facing different directions, you could drive that higher.

That approach is great. I use that now.

I’m probably going to use the two 4915AN controllers and do 2S2P on one and 2S or (unlikely) 2P on the other, and point the 2S SW but I’m doing something fairly ridiculously overpaneled so it might not have a noticeable effect. Dunno LOL?

 

[MisterSandals]

2S4P that would yield (nominal) 32A then I would be almost past the thin ice and falling into open water. Correct?

My understanding (based on the below) is no, because you are under 40A and hopefully NOT connecting reverse polarity.

If your array exceeds the PV input current limit and you connect your panels polarity-reversed, you may pop the controller.

When PV input current limit is not publish, it is presumed to be equal to the output current limit. In this case, 40A.

These are interesting tidbits that are good to know. I learned something today!

 

[Hedges]

Setting the stage
I have intentionally bought too many watts of panels not because I need the watts- but rather because I wish to have enough voltage to create usable charging in poor sun /overcast conditions.

Voltage doesn't drop much in low light conditions.

The below quote is in regards to a 100VOC models (I have two new-in-box Triron 4215AN units) but the principal is the same:

I haven't found 4215AN. 4215N I think says 150Voc max

https://www.amazon.com/EPEVER-Charge-Controller-Regulator-Triron4215N/dp/B07JPJ7BGM?th=1

Specifications
I have six “NOS” new panels:

REC Solar	72 Series
Model Number	REC315PE72
STC Rating	315.0
PTC Rating	288.4
Open Circuit Voltage (V)	45.5
Short Circuit Current (A)	9.09

45.5 Voc at nominal temperature

I have two 4215AN SCCs.

• Model: Triron4215N
• Rated charge current: 40 Amp
• Nominal system voltage:12V/24V DC
• Max. PV input power: 520W charge for 12V battery system / 1040W charge for 24V battery system
• Max. PV open circuit voltage:150V(at minimum operating environment temperature) ;138V(at 25℃ environment temperature)

Same 150V I found

• Grounding : Common negative
• Battery input voltage range : 8～32V
• MPP voltage range:V(BAT+2V)～72V
• Tracking efficiency : ≥99.5% , Max. conversion efficiency :98%

...

So the above Epever published specs indicate a max watts of charge as 520W for a 12V system for the 4215AN. One 2S string exceeds that slightly and I’m sure that’s not an over-panel issue.
However, what about 2S2P? Or even 3S3P?!

Don't do 3s, unless your location is warm enough that Voc won't rise more than 10%. That's 135Voc at nominal, so 150V max would be just 10% higher.

But will a 4215AN just simply not pass the “extra” ~700W? Or fry?

How much is too much- and why?​

An SCC could monitor current, temperature, etc. and back off to protect itself. Or it could process all available power, either shortening its life or causing immediate damage. Depends on how designed.

One reason for max Isc is reverse-polarity protection diodes, which shorts out the array. Maybe MPPT algorithm would also make excursions to max current without monitoring for limits.

We would hope that staying below max voltage and current ratings prevent over-stress but no guarantees.
Available wattage will make it run at full power, meaning higher current and self-heating. If it can be programmed for lower current limit, then your over-paneling would maintain production longer without peak heating (and power harvesting) middle of the day.

 

[sunshine_eggo]

Soooo… I’m reading that and my head is saying, “but the SCC limits the amps” but I think you mean if I- for example- did 2S4P that would yield (nominal) 32A then I would be almost past the thin ice and falling into open water. Correct?

I don't quite get the analogy.

2S4P should use Isc for this exercise. That's 36.4A. Still under 40A, so good.

So with one controller I would/could be ~32A 2S4P but unfortunately I bought the last six panels- I wanted eight.

36.4A

That approach is great. I use that now.

I’m probably going to use the two 4915AN controllers and do 2S2P on one and 2S or (unlikely) 2P on the other, and point the 2S SW but I’m doing something fairly ridiculously overpaneled so it might not have a noticeable effect. Dunno LOL?

I would stick with 2S?P for any array. Since you have two controllers, I think you're golden. Nowhere near hitting over-panel limits.

Buy more panels.

 

[Hedges]

2S4P should use Isc for this exercise. That's 36.4A. Still under 40A, so good.

If 2s2p oriented South West and another 2s2p oriented South East, those two then wired in parallel 2s4p, peak current would be about 0.7x as high and production flattened over a wider period of them.

Exact output will depend on tilt as well as orientation, the relative angle and area presented to sun, also something to do with reflection and anti-reflective coating behavior. So I'm just giving a rough estimate, haven't measured.

 

[sunshine_eggo]

If 2s2p oriented South West and another 2s2p oriented South East, those two then wired in parallel 2s4p, peak current would be about 0.7x as high and production flattened over a wider period of them.

Exact output will depend on tilt as well as orientation, the relative angle and area presented to sun, also something to do with reflection and anti-reflective coating behavior. So I'm just giving a rough estimate, haven't measured.

@Hedges and I are in total agreement.

You clearly don't have enough panels.

 

[DThames]

Read and understand the manual.

 

[sunshine_eggo]

Pretty convoluted manual with cautions and backpedals...



Basically operating in Condition 2 AND Condition 3, which isn't directly addressed, BUT don't go over 1.5X rated due to reasons that either don't matter (wasted modules - even though you're doing it on purpose) or can't happen with proper design (damage controller by overvolting it even if there's no possible way of reaching the Voc limits).

 

[DThames]

Pretty convoluted manual with cautions and backpedals...

View attachment 122252

Basically operating in Condition 2 AND Condition 3, which isn't directly addressed, BUT don't go over 1.5X rated due to reasons that either don't matter (wasted modules - even though you're doing it on purpose) or can't happen with proper design (damage controller by overvolting it even if there's no possible way of reaching the Voc limits).

My experience with the AN series is that they do a good job at current limiting to their design rating. It would be wise to make sure you have good airflow and mounting if one wants to run at the current limit for extended periods.

 

[MurphyGuy]

If its an Epever, I'm going to go with: The first panel or battery is too much.

People need to stop buying this Chinese garbage.

 

[pollenface]

If your array exceeds the PV input current limit and you connect your panels polarity-reversed, you may pop the controller.

Short circuit protection up to the rated input Isc. After that you're on your own ?

 

[DThames]

Short circuit protection up to the rated input Isc. After that you're on your own ?

Volt meter, great tool.

 

[Hedges]

Just be sure to put those red and black leads in the correct jacks.

Of course, modest over-current through reverse polarity protection diode is probably OK for a while. Isc spec may be for continuous wrong operation. Shut down right away if you see only ~ 1V.

 

[Bud Martin]

Epever is also known for output Voltage spike and causes inverter to go into over Voltage shutdown, there are threads about that bug, I.E.

A device that records max voltage?

What is the float voltage? That would be even lower around 26.8? Seems odd to get to 30+ in just a couple seconds while floating. Have you contacted epever? Quick google search indicates this is a general problem with this controller. Cloud edge effect or large change in load will effect the...

diysolarforum.com

 

[12VoltInstalls]

output will depend on tilt

Vertical to thwart snow
So there is a safety buffer for sure

Epever is also known for output Voltage spike and causes inverter to go into over Voltage shutdown, there are threads about that bug, I.E

i have experienced that myself. With lead acid. I’m thinking the modest volts needed for LiFePo should maybe curtail that.

@Hedges and I are in total agreement.
You clearly don't have enough panels

They are a bit uncommon in spec for typical retail but I may buy two if I can find them cheap. I already exceed my need by quite a bit lol

 

[12VoltInstalls]

don't quite get the analogy

Skating on thin ice…

Voltage doesn't drop much in low light conditions

what I meant was in poor light with say… 20V there are little if any amps. However, when I played games with 2S, 3S, and 4S series, I found that the more in series the more voltage the SCC was seeing on a cloudy day producing more amps than the sum of an equal number of single panels; and that I could see some amps earlier in the day and later in the day (minutes, i.e. not much).
That’s what I meant by volts. Not really volts, amps do the charging, but the summed volts seem to make more amps - marginal mind you- on poor light days.
That is the point of this exercise: to see what happens and maybe change if the hypothesis isn’t repeatable.

 

[mib]

@12VoltInstalls did you do what you wanted? everything works?

i want to do the same

AIO SRNE HF2430S60-100


my solar panels




2S2P are invested in VOC 100 volts and 40 amps PV, but quite much exceed 1400 watts, there is also a maximum PV of 1600 watts in the instructions

I also have a 40 amp mppt, but I would like to use only AIO

maybe tell me something?

 

[Hedges]

600W x 4 panels = 2400W (if all aimed at the sun)
If 2S aimed 90 degrees different from the other 2S, peak will be about 0.7x as high, 1700W peak. It will provide more uniform power through the day, a bit less total Wh compared to optimum orientation.