Clipping

[MrM1]

And @Sparky7

@SpongeboB Sinewave is like the E.F. Hutton of solar. When he talks people (should ) listen.

 

[MrM1]

I have two midnight classic cc. They were sized by the company I bought most of my equipment from so I believe they are good (maxt out though at full sun).

So this doesn't (clipping) have anything to do with my inverter size?

Classics can be over paneled no problem . If heat becomes an issue, there are "programing hacks" (I don't remember what it's called - but not in the usual programming menus ) where u can limit the Chargers charging out put amps (say from the 92 to 80 Amps) as a max. Then it runs cooler. It clips a little sooner but the FETS are notably cooler

 

[Sparky7]

Nope, the clipping is on the SCC, the inverter doesn't care about how much your panels are producing, just that there's enough voltage in the battery to run.

Oh, and we call the 180mph speed limiter in sports cars clipping as well.

The More You Know! ?

Ok, then I'm not worried about it. I thought my inverter was too small.

 

[Sparky7]

Awesome!

Thank you all for the help. That puts my mind at ease.

I bought the extra panels to help through the winter. I bought a whizzbang jr. and a relay to heat my domestic water with the extra power during the summer months. Hopefully, I can use most of the extra power.

 

[MrM1]

Your golden

 

[Sparky7]

As long as the charger or inverter is UL/ETL or otherwise NRTL "listed" (tested/approved) they will be tested for full output until at least they are temperature stable and lower than a certain temperature. Then another test or two are done.

Doesn't mean their life will not be reduced a bit if they run balls out every day but you over-panel because there are days when there are clouds and lower power than normal. If you're doing this every single day in and day out, then a second charger or inverter it probably a good idea.
Heat can slowly kill but should be OK. For a SCC/MPPT higher input voltage when running full power will generally heat the units up more for the same output power.

So if you can wire the unit for more power but less input voltage but reducing the number of PV in series and maybe parallel a string or two, the voltage will be lower and when it clips, it should run a bit cooler than with the higher voltage with same power of PV connected

There is another word used beside clipping... Flat topping. These refer to the output being limited like in the graph that was shown. Not the input.

boB

I thought the YouTube video I saw on clipping was referring to the inverter being to small. I didn’t know what the inverter had to do with this but I don’t know much about solar yet. I’m sure my two midnight classic 150s are sized properly. The company I bought most of my equipment from sized everything.

 

[Ampster]

So as long as you keep the voltage in the inverter range, there is no worry about “clipping” doing any damage?

Just to clarify, clipping does not causes damage. Over paneling can cause damage as you point out if voltage goes over spec. Clipping in my mind is a current related situation when the SCC or MPPT maxes out on the current it can pull or process from solar panels.

 

[SpongeboB Sinewave]

Just to clarify, clipping does not causes damage. Over paneling can cause damage as you point out if voltage goes over spec. Clipping in my mind is a current related situation when the SCC or MPPT maxes out on the current it can pull or process from solar panels.

As far as I am aware, most controllers and inverters will limit based on the output current into the batteries. They could also limit based on the input current. The Classic can do this but that adjustment is mainly for micro-hydro so that the turbine doesn't bog down.

If a SCC/MPPT is "ALWAYS" at its limit, every day of the year, then I would call that an over-sized array for sure and power is more than likely being wasted. But then again, solar is cheap these days so maybe the charge controller or inverter should be over-designed. If a company is doing that just so it can be over-paneled, they would be shooting themselves in the foot so to speak.

boB

 

[Sparky7]

As far as I am aware, most controllers and inverters will limit based on the output current into the batteries. They could also limit based on the input current. The Classic can do this but that adjustment is mainly for micro-hydro so that the turbine doesn't bog down.

If a SCC/MPPT is "ALWAYS" at its limit, every day of the year, then I would call that an over-sized array for sure and power is more than likely being wasted. But then again, solar is cheap these days so maybe the charge controller or inverter should be over-designed. If a company is doing that just so it can be over-paneled, they would be shooting themselves in the foot so to speak.

boB

So the inverter size can be a factor?

 

[Rednecktek]

No. Even in AIO's where the SCC is "integrated" into the unit, it's the SCC that controls how much power is pumped into the batteries.

If you had 50kw of panel on a 100a SCC, it would make zero difference whether you had a 200w inverter or a 200000w inverter. The SCC doesn't care at all what size the inverter is, the SCC would still be trying to pump 100a into the batteries.

The inverter only cares that there is enough voltage coming in to feed its load.

Tl;Dr: The inverter and SCC are 2 different components that have nothing to do with each other.

 

[MrM1]

Here is the White Paper to Limit charge current for the MNS Classic Chargers with Whizbang Jr installed. Useful if the SCC is over heating due to over paneling

MidNite Solar Classic Current Limiting with a WBjr White Paper

This is a TWEAK for Midnite Solar Classic Charge controllers to limit charge current. This can be useful in an over paneling situation where the charger charges full amps most of the time and is running hot. I have found at 24v and 92 amps...

diysolarforum.com

 

[Sparky7]

No. Even in AIO's where the SCC is "integrated" into the unit, it's the SCC that controls how much power is pumped into the batteries.

If you had 50kw of panel on a 100a SCC, it would make zero difference whether you had a 200w inverter or a 200000w inverter. The SCC doesn't care at all what size the inverter is, the SCC would still be trying to pump 100a into the batteries.

The inverter only cares that there is enough voltage coming in to feed its load.

Tl;Dr: The inverter and SCC are 2 different components that have nothing to do with each other.

That’s what I thought but some are mentioning the inverter in this discussion.

Thank you!

 

[Mattb4]

That’s what I thought but some are mentioning the inverter in this discussion.

Thank you!

I do see several people refer to an AIO as an inverter in discussions.

 

[FilterGuy]

That’s what I thought but some are mentioning the inverter in this discussion.

Thank you!

Yes. It gets confusing. The AIOs have an inverter, an AC charger, an SCC, and a transfer switch all in the same box. We tend to get lazy and just say 'inverter' when we mean one of the other components

 

[SpongeboB Sinewave]

So the inverter size can be a factor?

Yes, size is the factor here.

Clipping is only because the charger is too small, power wise, for the input source's capacity.

Of course the power will be reduced when the battery is full or the system cannot be allowed to sell more power than it is capable of, but that is a different story than clipping or power limiting.

boB

 

[OPTIMALSOLAR]

I don't know, but in my opinion, clipping is simply panel waste if you tie inverters that can't handle the panels. I've heard all the reasoning as to why 25% and more clipping is acceptable, but why accept it when it's not necessary? 20 400 watt panels simply produce more with Iq7A's than Iq7 pluses. Similarly if string inversion then an inverter that can handle 8kw of pv input/production will outproduce a 6 kw inverter. There is no instance when they perform poorer and a whole lot of time when they produce considerably better. Sure you can add more panels, to overcome clipping, but why? That is the fix, right? I have 2 systems. One clips one does not. The one that does not is far more efficient per kw and the panels are of lower quality and shaded more.

Anything more than 10% clipping imo, should be avoided unless very shady location, thus very rarely maxing panels, and sadly questionable if solar is a good idea at all, or beyond the panel's string limitations. I'd suggest those are rare instances. Of course if maxing 400 watt panels at 295 watts is acceptable. ok.

 

[Ampster]

I don't know, but in my opinion, clipping is simply panel waste if you tie inverters that can't handle the panels.

Yes, but it is not a waste from an inverter standpoint. The more my inverter runs close to 100 percent of capacity the more optimal my system is.

I've heard all the reasoning as to why 25% and more clipping is acceptable

I guess it depends on how you measure that 25 percent clipping, and over what period, I am more concerned with overall production throughout the year. If a higher DC to AC ratio gets me a better total production than a lower ratio with the same inverter I would not be concerned about clipping.

 

[OPTIMALSOLAR]

Absolutely it is not inverter waste. Which costs more the panels or the inverters in total?


And ya sure more DC always mean more production. As does greater inversion. Which costs more, panels or inverters?

 

[Ampster]

Which costs more the panels or the inverters in total?

In addition, in some cases a larger inverter might require a larger service panel in which case it is an entirely different financial calculation. Typically adding an additional or two panel is less expensive than increasing the size of an inverter, because inverter sizes increase in larger increments. The exception is micros. In addition, a system that might be clipping when new might not clip much as panels degrade over time and that would mean an inverter that is underutilized.

 

[OPTIMALSOLAR]

The exception is micros.

Micros are a rather large exception.




In addition, a system that might be clipping when new might not clip much as panels degrade over time and that would mean an inverter that is underutilized.

Really? How long does it take for solar panels to degrade by 25%. I think it's about 50 years. 70 for your Sunpowers. Even 10% panel clipping. Thats' 20 years of clipping. Not enough? Also do any string inverters spec at 20 years for lifecycle? Enphase says 25. Hopefully they will. Got 20 of those clipping bastards. They better be 2x as reliable else why have them.