PV input readings on All-in-One with MPPT inaccurate leading to loss in power

[52388]

Hi, I have a Voltronic solar inverter (24v 3kva, 1500w pv with mppt range 30-115 vdc) and one 320 watt solar panel (vmp 37, imp 8.65).
My issue is that I have a lower input reading from my panel than expected, peaked at around 180 watts, but the actual readings on a clamp multimeter were 32 volts + 8.5 amps, that gives out 270 watts. I didn't have this issue with a different but 12 volt inveter, it gave out all that power.
Is the voltage not enough for the mppt to start tracking or is it something else?
BTW, Occasionaly, after a cloud emerge and then pass, the input spiked 210-215 watts for a short time.

I live in Gaza and solar panels are out-of-this-world expensive so I need this to give all the power it can.
Thanks.

 

[timselectric]

Yes, the voltage is low for the charger.
You are barely getting enough to wake it up. And as soon as it starts applying the load, the voltage is pulled down.

 

[52388]

Yes, the voltage is low for the charger.
You are barely getting enough to wake it up. And as soon as it starts applying the load, the voltage is pulled down.

why is it pulling 32v * 8.5a tho? Where does the excess power go? heat? It does get warm for a "180w" system I can say.

 

[Will Prowse]

why is it pulling 32v * 8.5a tho? Where does the excess power go? heat? It does get warm for a "180w" system I can say.

It's not being used at all. Technically the solar panel temp will rise when you're not pulling current from it.

You need at least 3 of those panels in series for a 24V battery and good performance.

I'm surprised that single panel is doing anything at all. You're right on the threshold of startup voltage once panel voltage drops.

 

[Will Prowse]

Hi, I have a Voltronic solar inverter (24v 3kva, 1500w pv with mppt range 30-115 vdc) and one 320 watt solar panel (vmp 37, imp 8.65).
My issue is that I have a lower input reading from my panel than expected, peaked at around 180 watts, but the actual readings on a clamp multimeter were 32 volts + 8.5 amps, that gives out 270 watts. I didn't have this issue with a different but 12 volt inveter, it gave out all that power.
Is the voltage not enough for the mppt to start tracking or is it something else?
BTW, Occasionaly, after a cloud emerge and then pass, the input spiked 210-215 watts for a short time.

I live in Gaza and solar panels are out-of-this-world expensive so I need this to give all the power it can.
Thanks.

With 12V nominal the start up voltage for solar charge controller is much lower. 24V needs a higher voltage.

 

[52388]

It's not being used at all. Technically the solar panel temp will rise when you're not pulling current from it.

You need at least 3 of those panels in series for a 24V battery and good performance.

thanks for replying, fan of your videos!
I understand, but to be more clear the measurement (270w which is expected vs 180w on SCC) was taken while the panel was attached to the unit, operating, and loaded. Is it still not being used according to your statement?
I am new to solar systems, but I gained good-enough knowledge fast, thanks to your videos as well.
I had the same suspicions that 12 volt system has lower nominal voltage thus gaining full power, I guess I try to keep gaslighting my self into thinking the issue is not enough voltage, not that I have a faulty charger. Hope thats the case, The inverted costs 1700$ (actually exchanged it with a previously owned 4000 watts 120-450 SCC) and the solar panel is 1400$

 

[Will Prowse]

thanks for replying, fan of your videos!
I understand, but to be more clear the measurement was taken while the panel was attached to the unit, operating, and loaded. Is it still not being used according to your statement?
I am new to solar systems, but I gained good-enough knowledge fast, thanks to your videos as well.
I had the same suspicions that 12 volt system has lower nominal voltage thus gaining full power, I guess I try to keep gaslighting my self into thinking the issue is not enough voltage, not that I have a faulty charger. Hope thats the case, The inverted costs 1700$ (actually exchanged it with a previously owned 4000 watts 120-450 SCC) and the solar panel is 1400$

Oh no it's working, you'll just have bad performance.

No it's not the controller. You need more solar panels.

Where in the world are you located. Solar panel should never be that expensive

 

[52388]

Oh no it's working, you'll just have bad performance.

No it's not the controller. You need more solar panels.

Where in the world are you located. Slurp panel should never be that expensive

Located in Gaza, Surely you know whats going on overhere. Bare minimum survival food is more expensive than any many solar panels.

 

[Mattb4]

Hi, I have a Voltronic solar inverter (24v 3kva, 1500w pv with mppt range 30-115 vdc) and one 320 watt solar panel (vmp 37, imp 8.65).
My issue is that I have a lower input reading from my panel than expected, peaked at around 180 watts, but the actual readings on a clamp multimeter were 32 volts + 8.5 amps, that gives out 270 watts. ...

I doubt your clamp multimeter reads both voltage and current at the same time. Without doing that you are not actually getting 270W. Even with a voltage readout and a dead short current reading it does not mean the solar panel is is actually capable of producing the calculated wattage. Once you load a panel down is where you can get actual numbers.

Now there is another thing to look at. Does your Voltronic AIO have a setting for PV current? If this is set lower than the panels capability to produce than you will limit output. Example your 180W at 12vDC nominal battery voltage. This is a charge current of 15A. In order to max out for a 320W panel you will need a PV charge rate of around 30A.

 

[52388]

I doubt your clamp multimeter reads both voltage and current at the same time. Without doing that you are not actually getting 270W. Even with a voltage readout and a dead short current reading it does not mean the solar panel is is actually capable of producing the calculated wattage. Once you load a panel down is where you can get actual numbers.

Now there is another thing to look at. Does your Voltronic AIO have a setting for PV current? If this is set lower than the panels capability to produce than you will limit output. Example your 180W at 12vDC nominal battery voltage. This is a charge current of 15A. In order to max out for a 320W panel you will need a PV charge rate of around 30A.

The measurements were done while the panel is connected and loaded to the unit, it was a not a short circuit nor an open circuit, simply clamp the wires right before the pv input terminals or screws, once for voltage, which was 32 vdc, and another on a single wire for pulled current, which in this case was 8.5A, these values indicated a loaded panel becauce the VOC of the panel is 42V and the Isc is 9.6. voltage drop due to heat and wiring is about 5 volts for the panel Vmp (37).
As for the charging current it is set the highest possible, and my system is 24V. Thanks.

 

[52388]

I doubt your clamp multimeter reads both voltage and current at the same time. Without doing that you are not actually getting 270W. Even with a voltage readout and a dead short current reading it does not mean the solar panel is is actually capable of producing the calculated wattage. Once you load a panel down is where you can get actual numbers.

Now there is another thing to look at. Does your Voltronic AIO have a setting for PV current? If this is set lower than the panels capability to produce than you will limit output. Example your 180W at 12vDC nominal battery voltage. This is a charge current of 15A. In order to max out for a 320W panel you will need a PV charge rate of around 30A.

PS: I wanted to measure the charging current via MM to the batteries to see if its just a faulty read, i'll post you when i do.

 

[Mattb4]

The measurements were done while the panel is connected and loaded to the unit, it was a not a short circuit nor an open circuit, simply clamp the wires right before the pv input terminals or screws, once for voltage, which was 32 vdc, and another on a single wire for pulled current, which in this case was 8.5A, these values indicated a loaded panel becauce the VOC of the panel is 42V and the Isc is 9.6. voltage drop due to heat and wiring is about 5 volts for the panel Vmp (37).
As for the charging current it is set the highest possible, and my system is 24V. Thanks.

If your voltage reading at the AIO is multiplied by your clampmeter current reading (thus both at the same time) this gives you a method to determine PV output wattage. If your AIO is not displaying the same wattage than its sensors or method of calculating incoming wattage is in error. Not a unusual situation with the less expensive AIO's. As you mention the charging current to your battery and voltage will provide another check.

Sorry about the 12v/24v mix up.

 

[52388]

If your voltage reading at the AIO is multiplied by your clampmeter current reading (thus both at the same time) this gives you a method to determine PV output wattage. If your AIO is not displaying the same wattage than its sensors or method of calculating incoming wattage is in error. Not a unusual situation with the less expensive AIO's. As you mention the charging current to your battery and voltage will provide another check.

Sorry about the 12v/24v mix up.

Oh no it's working, you'll just have bad performance.

No it's not the controller. You need more solar panels.

Where in the world are you located. Solar panel should never be that expensive

UPDATE: so I measured the charging current of the batteries (No load, Switch off) and it was a tad more than the pv input current, about 8.5-8.7A at 27-28V whilst pv input was 8.2A at 32V. This case looks benign now as little power is lost compared to the display readings, which were 6-7A at the time of measuring.

Yes, maybe I could get more power with more tracking if voltage is increased, but thats fine for now, upgrading later.
Any thoughts? Happy to have mistakes pointed out to me.

 

[Will Prowse]

UPDATE: so I measured the charging current of the batteries (No load, Switch off) and it was a tad more than the pv input current, about 8.5-8.7A at 27-28V whilst pv input was 8.2A at 32V. This case looks benign now as little power is lost compared to the display readings, which were 6-7A at the time of measuring.

Yes, maybe I could get more power with more tracking if voltage is increased, but thats fine for now, upgrading later.
Any thoughts? Happy to have mistakes pointed out to me.

Still need higher voltage. You're right on the threshold so morning and afternoon performance will be pretty bad. Add another panel when possible.