PV Arrangement?

[D. Abineri]

You have to understand that the voltage the panels are producing can vary by large amounts over the course of a day. I've seen the Vmp vary from 89V to 124V from my arrays with clear sunny weather over the course of the day, and depending on the load applied.

The 110V value is the "working" limit, with a built-in safety factor to account for load and temperature changes. The 145V limit is the drop-dead limit when exceeded the electronics go poof and make pretty fireworks!

The Voc is the highest voltage that the panels can produce under open circuit conditions. That typically happens every single time the controller senses the battery is fully charged and stops current flowing to the batteries. When the controller switches back on, the electronics are exposed that Voc until the load drops it down to Vmp.

BTW, the voltage limit does limit the maximal power coming in, but that is compensated for by adding parallel strings of more panels. With each string bringing in only 8amps, at say 112V, you get more power by adding more parallel strings, up to 80amps.

Michaelk, Thanks, this all makes perfect sense now. However, it would mean that the 145v spec really does not mean anything and, in my opinion, only leads to confusion about the limits on the inverter and charger. Thanks for your help.

 

[Just John]

Michaelk, Thanks, this all makes perfect sense now. However, it would mean that the 145v spec really does not mean anything and, in my opinion, only leads to confusion about the limits on the inverter and charger. Thanks for your help.

No, it means something and is very useful.
It means don't exceed 145v on the solar input, or the magic smoke escapes. I find that information very useful,

 

[D. Abineri]

No, it means something and is very useful.
It means don't exceed 145v on the solar input, or the magic smoke escapes. I find that information very useful,

I agree that this is useful for the inverter circuitry. But you will already have fried your charger at that point if I understand correctly.

 

[Just John]

I agree that this is useful for the inverter circuitry. But you will already have fried your charger at that point if I understand correctly.

Since we are talking about the input limitations on the solar charge controller, I'm missing why this is related to the inverter, other than the unit combines them.

 

[D. Abineri]

Since we are talking about the input limitations on the solar charge controller, I'm missing why this is related to the inverter, other than the unit combines them.

The lv5048 inverter indicates that the max dc input voltage is 145v. However, I am told not to exceed 110v which is the max that the charge controller can deal with. So, why does it not say that the max dc input is 110v rather than 145v so as to avoid damaging the charger?

 

[Just John]

The lv5048 inverter indicates that the max dc input voltage is 145v. However, I am told not to exceed 110v which is the max that the charge controller can deal with. So, why does it not say that the max dc input is 110v rather than 145v so as to avoid damaging the charger?

Read post #18 in this thread.

You can get panels that have 110v working voltage that will fry your solar charge controller because their open circuit voltage exceeds 145v.

Both numbers are relevant, and important.

 

[D. Abineri]

Read post #18 in this thread.

You can get panels that have 110v working voltage that will fry your solar charge controller because their open circuit voltage exceeds 145v.

Both numbers are relevant, and important.

I understand what you are saying, but I would have thought that, with all the software controlling the inverted/charger that they would have built in a software cut-off to avoid frying any hardware. Is there a parameter that sets a max charger input voltage, for example?

 

[Just John]

I understand what you are saying, but I would have thought that, with all the software controlling the inverted/charger that they would have built in a software cut-off to avoid frying any hardware. Is there a parameter that sets a max charger input voltage, for example?

You should ask the hardware manufacturer and design engineer. Hardware is not defined by software, and we are talking a hardware limit.
Splitting hairs with me about how you think it should work, doesn't make it work that way.

Both numbers are relevant, and you should pay attention to them.

Sort of like plugging a clothes dryer into a 120 volt outlet, just because you think it should work, doesn't mean it will.
Pay attention to the outlet and the plug, or else bad things happen.

 

[D. Abineri]

You should ask the hardware manufacturer and design engineer. Hardware is not defined by software, and we are talking a hardware limit.
Splitting hairs with me about how you think it should work, doesn't make it work that way.

Both numbers are relevant, and you should pay attention to them.

Sort of like plugging a clothes dryer into a 120 volt outlet, just because you think it should work, doesn't mean it will.
Pay attention to the outlet and the plug, or else bad things happen.

I agree with all you say but my point is that, as a beginner, I asked the question as to how best to arrange my panels. The answers that came back all said that "you don't want to get too close to the 145v limit of the inverter" so as not to fry it. So, as a beginner, it never occurred to me that other limitations ( like the charger limits) might come into play also as no one seemed to worry about that until this issue with the charger came up. I guess that there are others who offered me their original advice that did not understand the charge limitation also..

 

[wattmatters]

The answers that came back all said that "you don't want to get too close to the 145v limit of the inverter" so as not to fry it. So, as a beginner, it never occurred to me that other limitations ( like the charger limits) might come into play also as no one seemed to worry about that until this issue with the charger came up.

There are two voltage ranges.

One is the effective working range for an MPPT to operate within and enable the inverter to generate output. The system works most effectively when voltage is within this range. Too few or too many panels in series means the MPPT may not be able to operate.

The other value is the inverter's upper voltage connection limit before bad things happen.

Exceeding the MPPT operating range while not exceeding the upper voltage limit just means your inverter is not generating output as efficiently as it might otherwise do, but it is not unsafe or damaging to your system.

But exceeding the upper voltage limit runs the real risk of causing damage to your inverter, and potentially to you.

 

[wattmatters]

The only loose analogy I can think of is an engine.

Engines all have an RPM range at which they are most effectively operated within. If RPM is too low it can stall or bog down. It might be able to chug along but won't necessarily be terribly efficient. If RPM is too high, then power and efficiency drops. A gearbox is a bit like an MPPT, it constantly seeks to keep the engine operating in the right RPM band for best performance.

Engines will also have an upper RPM limit beyond which stuff can go seriously wrong. This is like the inverter's upper voltage connection limit.

It's not a perfect analogy (none are) but hopefully this gives some idea of why there are different limits.

 

[D. Abineri]

The only loose analogy I can think of is an engine.

Engines all have an RPM range at which they are most effectively operated within. If RPM is too low it can stall or bog down. It might be able to chug along but won't necessarily be terribly efficient. If RPM is too high, then power and efficiency drops. A gearbox is a bit like an MPPT, it constantly seeks to keep the engine operating in the right RPM band for best performance.

Engines will also have an upper RPM limit beyond which stuff can go seriously wrong. This is like the inverter's upper voltage connection limit.

It's not a perfect analogy (none are) but hopefully this gives some idea of why there are different limits.

GOT IT! Thanks for all your time educating me, it is appreciated.