Curiousities of Charge Controller "Clipping" (terminology??)

[Robert1234]

I may be using the wrong terminology, but think I read somewhere on this board that charge controller "clipping" is when you feed more power into the CC than the system is capable of outputting. I'd like to understand this more to insure I do not damage equipment.

I have a Xantrex XW-MPPT-60 charge controller and currently have up to ~ 3 kWatt of ground array installed that I can configure to the CC in anyway I choose (15 x 200 watt panels). Simply stated, my understanding is that this charge controller can handle 60 amp input and output. So, theoretically, the controller should be able to handle all the panels being fed to it (5 banks of 600w @ 90 volts = 33 amp in) While servicing a 48v battery bank (~ 60 amp out).

If I only have a 24v bank configured, I'd only be harvesting 50% power at peak production due to the CC's 60 amp limit on the output. Will the CC limit itself to 60 amp output and just reduce current? or would it be damaged?

[Sunking]

Real simple for MPPT max output current is Panel Wattage / Battery voltage. When panel wattage is greater than supported the amps are clipped and not used.

A panel is a current source at MPPT voltage and lower. Above MPPT a panel is a voltage source. Do not exceed the CC max input wattage vs battery voltage. The limit on your MX 60 @ 48 volt battery is 3200 watts.

[Robert1234]

Real simple for MPPT max output current is Panel Wattage / Battery voltage.When panel wattage is greater than supported the amps are clipped and not used and the panel voltage operate at a higher voltage than MPPT.

A panel is a current source at MPPT voltage and lower. Above MPPT a panel is a voltage source.

Thanks. That's what I was hoping to hear, but I don't want to misinterpret because that is what I was wanting for an answer

Just want to be sure I understand you correctly... "clipped" is inefficient, but NOT harmful to the charge controller. Correct?

Thanks again.

[Sunking]

That's what I was hoping to hear, but I don't want to misinterpret because that is what I was wanting for an answer

Lets' get one thing straight, I do not answer to tell you what you want to hear OK. I give my answers on facts which I have learned in 30+ years of experience.

Just want to be sure I understand you correctly... "clipped" is inefficient, but NOT harmful to the charge controller. Correct?

No sir not inefficient. Design tolerances. Keep in mind solar panels are overrated and never generate the specified power. CC manufactures know this and design a bit of overkill in there design. Some are better than others.

For example for a Apples to Apples comparison look at the Outback MX 80 and Midnight Solar Classic 150. Both are 80 amp MPPT Controllers. At 48 volts:

Outback MX80
Max input = 5000 watts
Max Current = 80 amps

Midnight Solar
Max input = 5022 watts
Max Current = 86 amps

Drop the spec down to 12 volt battery:

Outback MX80
Max Input = 1250
Max current = 80 amps

Midnight Solar
Max input = 1380
Max Current = 92 amps

[inetdog]

Thanks. That's what I was hoping to hear, but I don't want to misinterpret because that is what I was wanting for an answer

Just want to be sure I understand you correctly... "clipped" is inefficient, but NOT harmful to the charge controller. Correct?

Thanks again.

On the other hand, a particular MPPT CC or GTI manufacturer may include in its specifications a maximum allowed panel wattage. If they do, you do not (without asking them) know why they did that. And it may be that there is a reason involving potential damage to the CC or GTI.

A PWM CC is more likely to be vulnerable to damage by too high an instantaneous current capability from the panels.

There is no harm in clipping as long as you do not exceed the manufacturer's specifications along the way.
And you can be absolutely sure that there will be no damage to the panels, since they are quite content delivering less than their rated power.

[Sunking]

I withheld info earlier because it is not something I recommend. I eluded earlier a panel does not produce its rated power. With that said you can install higher than specified wattage, but you had better know what you are doing, and I am not going to tell you how.

[Robert1234]

Lets' get one thing straight, I do not answer to tell you what you want to hear OK. I give my answers on facts which I have learned in 30+ years of experience.

Exactly what I would hope for and certainly need. Too often in business we see and hear what we want to in data that is presented. I was simply clarifying what I believed I was hearing to insure I did not fall into that trap.

Anyway, I do appreciate your responses. Thank you again.

[Sunking]

Exactly what I would hope for and certainly need. Too often in business we see and hear what we want to in data that is presented. I was simply clarifying what I believed I was hearing to insure I did not fall into that trap.

Anyway, I do appreciate your responses. Thank you again.

Sorry been a bad day. Fixing to head to Moore OK and help out.

[Robert1234]

No problem. Stay safe.

[SunEagle]

Sorry been a bad day. Fixing to head to Moore OK and help out.

Take care Sunking. I know you will make a difference for those poor people.