MPPT working range

[hugobenjegard]

Hi,

I'm looking at getting this all in one inverter ( https://www.aliexpress.com/item/100...5aa9b3142fda7b43da864d26b2b&afSmartRedirect=y ) and the starting voltage of the MPPT is 55v.
My PV array will consist of 2 panels with a voc of 50.3 in series so 100.6 in total.
Will the voltage be to low for the MPPT to function correctly or would this work? The setup will be for a van so I don't have space for more panels on the roof. But I'll be able to tilt them to get better exposure when the sun is lower.

Thanks for all answers and advice, any input is greatly appreciated!

 

[sunshine_eggo]

Consult the Vmp of the panels. Would expect they're around 80Vmp in series. I would assume you would have no issues.

 

[GXMnow]

According to the listed specs it should work.
Even under load, your panels should stay over 60 volts. That is in the quoted MPPT range.
There is no listing for how efficient it will be at your low voltage, but I see no reason why it would not charge.

 

[hugobenjegard]

Consult the Vmp of the panels. Would expect they're around 80Vmp in series. I would assume you would have no issues.

Yeah the vmp is 39.7 so around 80 for the pair. Would that still be enough in lower light conditions though? Thanks! Spec sheet attached below, it's the 430w version I'm looking at.

 

[hugobenjegard]

According to the listed specs it should work.
Even under load, your panels should stay over 60 volts. That is in the quoted MPPT range.
There is no listing for how efficient it will be at your low voltage, but I see no reason why it would not charge.

Thanks! I think I'll go for it then and in worst case I might buy a MPPT with a lower voltage range if the yield isn't great!

 

[sunshine_eggo]

Yeah the vmp is 39.7 so around 80 for the pair. Would that still be enough in lower light conditions though? Thanks! Spec sheet attached below, it's the 430w version I'm looking at.

Lower light conditions = crappy performance, no matter what.

STC = 42.3V, so 84.6Vmp

From your datasheet:



Peak power is always really close to Vmp. The idea that very high PV voltage is meaningfully better is vastly overstated. You might get 10% better performance on 10% rated performance, i.e., 1% improvement against the rated output of the array.

Vmp decreases when cell temperatures increase, so in summer with hot cells, you might see the NOCT Vmp ratings of 39.7 or 79.4V - still above 55V.

 

[GXMnow]

We still have clouds and the sun is barely over the horizon here.

My new Victron MPPT charge controller is only a 150 volt version, but for this discussion, I think that data is relevant.

My VOC is about 110 volts, and the VMP would be about 90 volts. With this tiny bit of sunlight getting through, the array is running at 84 volts, so even at very low light, the voltage does not drop much below the VMP. But the current at such a low light is only 0.3 amps at the array. After the DC to DC converter, it is putting just 0.5 amps into my battery bank.

Yup, what he said above.
The voltage stays fairly constant.

 

[hugobenjegard]

Lower light conditions = crappy performance, no matter what.

STC = 42.3V, so 84.6Vmp

From your datasheet:

View attachment 190863

Peak power is always really close to Vmp. The idea that very high PV voltage is meaningfully better is vastly overstated. You might get 10% better performance on 10% rated performance, i.e., 1% improvement against the rated output of the array.

Vmp decreases when cell temperatures increase, so in summer with hot cells, you might see the NOCT Vmp ratings of 39.7 or 79.4V - still above 55V.

Awesome, thanks a lot for the help! Didn't see the voltage drop table before posting the thread. Looking at it it really seems like staying over 55v should be any problem!

 

[hugobenjegard]

We still have clouds and the sun is barely over the horizon here.

My new Victron MPPT charge controller is only a 150 volt version, but for this discussion, I think that data is relevant.

My VOC is about 110 volts, and the VMP would be about 90 volts. With this tiny bit of sunlight getting through, the array is running at 84 volts, so even at very low light, the voltage does not drop much below the VMP. But the current at such a low light is only 0.3 amps at the array. After the DC to DC converter, it is putting just 0.5 amps into my battery bank.

Yup, what he said above.
The voltage stays fairly constant.

Thanks for the help mate, as long as the voltage is high enough for the MPPT to work it should be fine. I'm planning on being in pretty sunny conditions but my main worry was the MPPT not even starting cause of low voltage.

 

[sunshine_eggo]

Thanks for the help mate, as long as the voltage is high enough for the MPPT to work it should be fine. I'm planning on being in pretty sunny conditions but my main worry was the MPPT not even starting cause of low voltage.

Starting voltage depends on Voc. Running voltage is Vmp. The MPPT will see the Voc (~100V) and start without issue. Staying above 55V is what's needed to keep the MPPT function working.

Assuming flat panels on a vehicle roof - do your best to ensure there is at least a small gap to allow for panel cooling.

Additionally, in Sweden, I expect your winter performance with panels flat on a roof is going to be absolutely horrible... maybe 20% of rated. Either need to tilt them South to an extreme angle (65°) or get some temporary panels and hang them from the South facing side (4X flexible 100W panels hanging from the side (in series) in parallel with your roof array would dramatically improve production).

 

[hugobenjegard]

Starting voltage depends on Voc. Running voltage is Vmp. The MPPT will see the Voc (~100V) and start without issue. Staying above 55V is what's needed to keep the MPPT function working.

Assuming flat panels on a vehicle roof - do your best to ensure there is at least a small gap to allow for panel cooling.

Additionally, in Sweden, I expect your winter performance with panels flat on a roof is going to be absolutely horrible... maybe 20% of rated. Either need to tilt them South to an extreme angle (65°) or get some temporary panels and hang them from the South facing side (4X flexible 100W panels hanging from the side (in series) in parallel with your roof array would dramatically improve production).

Thanks, the plan is to be in southern Europe or maybe even the Canary Islands during winter so we'll get much better production than here, thanks again for the help mate it is greatly appreciated! I don't know how I'd have figured this out on my own!

 

[sunshine_eggo]

Thanks, the plan is to be in southern Europe or maybe even the Canary Islands during winter so we'll get much better production than here, thanks again for the help mate it is greatly appreciated! I don't know how I'd have figured this out on my own!

I did most of my stuff before finding this site. My process was:

1. Trial
2. Error
3. More money
4. Go to 1

 

[hugobenjegard]

I did most of my stuff before finding this site. My process was:

1. Trial
2. Error
3. More money
4. Go to 1

Yeah that would be me as well if this site didn't exist, will probably still be doing a bit of trail and error but much less thanks to people like yourself sir!

 

[scrubjaysnest]

I did most of my stuff before finding this site. My process was:

1. Trial
2. Error
3. More money
4. Go to 1

Been there done that and yes I have the tee shirt.