Solar Panel Size?

[Naughty Cal]

We were led to believe (by the salesman and manufacturers blurb) that the solar panel installed on the van was a 150w panel.

 

However today while it's been out having its spring clean, parked in full March sun it has been outputting a pretty much constant 7 amps as measured by the Victron solar controller and the Sterling Amps battery which seems to be too much for a 150w panel in March sun.

 

There are no markings or makers marks we can see on the panel (although we assume it is CBE as everything else is/was) so they must be on the underside which we can't get at without unbonding it from the roof.

 

Any other ways we can guesstimate it's size?

 

It's a fairly big panel, the van is 2.3m wide (mirrors folded) and it spans most of the roof.

 

 

Don't really fancy pulling it off the roof to find out! 

[IanD]

11 minutes ago, Naughty Cal said:

We were led to believe (by the salesman and manufacturers blurb) that the solar panel installed on the van was a 150w panel.

 

However today while it's been out having its spring clean, parked in full March sun it has been outputting a pretty much constant 7 amps as measured by the Victron solar controller and the Sterling Amps battery which seems to be too much for a 150w panel in March sun.

 

There are no markings or makers marks we can see on the panel (although we assume it is CBE as everything else is/was) so they must be on the underside which we can't get at without unbonding it from the roof.

 

Any other ways we can guesstimate it's size?

 

It's a fairly big panel, the van is 2.3m wide (mirrors folded) and it spans most of the roof.

 

 

Don't really fancy pulling it off the roof to find out! 

 

If you measure the panel size, you can then compare it to panels here to see what the likely output (in full summer sun at midday) is:

 

https://www.bimblesolar.com/panelcompare?sort=price_per_watt

Edited March 24 by IanD

[Alan de Enfield]

Is that the current going into the batteries ?

 

My 170w panel is producing at 120 volts so I am getting roughly 8x the panel current going into the batteries.

 

If your panel is similar, then yes I can easily believe that the panel is producing X amps at 120v so 7 amps at 12 volts.

 

What is the panel output voltage and what was the battery voltage when you saw the 7 amps ?

 

 

An example of mine when the Sun was not too strong.

Outputting 0.8amps at 103 volts. 'contverting' that to 5.9 amps at 14.7 volts

 

 

 

Edited March 24 by Alan de Enfield

[Naughty Cal]

Yes current into the battery.

[Alan de Enfield]

2 minutes ago, Naughty Cal said:

Yes current into the battery.

 

And what voltage is the panel and what output voltage was it showing ?

What voltage was the battery at ?

[Naughty Cal]

52 minutes ago, Alan de Enfield said:

 

And what voltage is the panel and what output voltage was it showing ?

What voltage was the battery at ?

To be honest I wasn't taking much notice but will assume panel voltage was at or similar to the maximum recorded today on the solar controller. 

 

So around 12.78v.

 

No idea what the battery voltage was other than over 13.26v (Sterling Amps lithium) unfortunately didn't take any notice of that!

 

 

Will take more notice next weekend when we are out. No point in the week as its parked on the north side of the house all week in the shade 🙄

[Alan de Enfield]

1 minute ago, Naughty Cal said:

To be honest I wasn't taking much notice but will assume panel voltage was at or similar to the maximum recorded today on the solar controller. 

 

So around 12.78v.

 

I very much doubt that - the panel voltage would not be the same as the battery or it would never charge, Generally the panel voltage would be a minimum of ~20v, many are much higher (as stated mine is 120v panel).

[Naughty Cal]

1 minute ago, Alan de Enfield said:

 

I very much doubt that - the panel voltage would not be the same as the battery or it would never charge, Generally the panel voltage would be a minimum of ~20v, many are much higher (as stated mine is 120v panel).

No that was 21.78 not 12.78!

[Francis Herne]

7 amps at, say, 14V is about 100W. That seems reasonable to me for a 150W panel in direct sunlight.

 

There's a significant temperature coefficient for solar panels, so I actually see higher peak outputs early in the year than mid-summer, although my often-angled panels will benefit less from the sun being high in the sky than your flat one.

 

Solar panels get very hot in direct summer sun - up to 75°C or so, losing about 1% of output for every 3° of temperature per the datasheet for mine. That's more than enough to outweigh the more favourable angle.

 

Of course total output is still much higher in the summer thanks to longer days and generally better weather.

Edited March 24 by Francis Herne

[magnetman]

I had some unusually high output from my solar today. 

 

I think it might have just been a very bright bit of sun and always worth bearing in mind that solar panels work better in colder weather and there was a terribly shocking northerly. 

 

 

[IanD]

5 hours ago, Naughty Cal said:

To be honest I wasn't taking much notice but will assume panel voltage was at or similar to the maximum recorded today on the solar controller. 

 

So around 12.78v.

 

No idea what the battery voltage was other than over 13.26v (Sterling Amps lithium) unfortunately didn't take any notice of that!

 

 

Will take more notice next weekend when we are out. No point in the week as its parked on the north side of the house all week in the shade 🙄

 

My panels (2kWp) have been averaging 4.4kWh/day (2.2x rating) over the last 3 days, peak power was 1430W (0.7x rating).

 

Assuming same amount of sun (very likely wrong!) a 150W panel would have averaged 330Wh/day and peaked at 105W.

Edited March 24 by IanD

[Naughty Cal]

6 hours ago, IanD said:

 

My panels (2kWp) have been averaging 4.4kWh/day (2.2x rating) over the last 3 days, peak power was 1430W (0.7x rating).

 

Assuming same amount of sun (very likely wrong!) a 150W panel would have averaged 330Wh/day and peaked at 105W.

It was only out in the bright sun for a couple of hours before it was put back in the shade.

[Jen-in-Wellies]

@Naughty Cal's van has a lithium battery, so it will take all the current that the panel can throw at it. The lack of clouds through much of yesterday would have made a huge difference to the panels output. Not surprised it was so high. We are past the spring equinox now, so the day star is getting higher in the sky.

[Higgs]

No load on the panel should be a little over 20v. In circuit, about 18v to 18.5v. 150w/18.5v = 8.1A  peak. Using an MPPT charge controller, it will reduce the voltage and increase the amperage. The lower light intensities in the UK will produce the voltage, but not the current that the panel would be capable of in optimum circumstances. It would be up to the charge controller to increase the current, by reducing the voltage.

 

 

 

 

Edited March 25 by Higgs

[Momac]

The data below from Renology states 100W from a 1.062m x 0.53m panel. That comes to 177W per square metre while the Renology 200W panel is almost exactly 1 square metre .

 A domestic solar installer on the internet claimed more like 150W per square metre which may be more of a real life expectation.

 

 

[Tacet]

11 hours ago, IanD said:

 

My panels (2kWp) have been averaging 4.4kWh/day (2.2x rating) over the last 3 days, peak power was 1430W (0.7x rating).

 

Assuming same amount of sun (very likely wrong!) a 150W panel would have averaged 330Wh/day and peaked at 105W.

I can see what you mean - but I find these units confusing.  It seems odd that peak power is 0.7 somethings and yet the average is 2.2 somethings.

[Alan de Enfield]

1 hour ago, Tacet said:

I can see what you mean - but I find these units confusing.  It seems odd that peak power is 0.7 somethings and yet the average is 2.2 somethings.

 

 

My reading is that

1) His panels total 2kW

2) On average over the last 'few days' the daily total generated has been 4.4Kwh/day

3) The highest instaneous 'peak' reading has been 1430w (which may have been only for a couple of seconds)

[magnetman]

Both of these figures will be shown on the Victron or other application display. 

 

Maximum actual output and total output during daylight. 

 

 

[IanD]

1 hour ago, Alan de Enfield said:

 

My reading is that

1) His panels total 2kW

2) On average over the last 'few days' the daily total generated has been 4.4Kwh/day

3) The highest instaneous 'peak' reading has been 1430w (which may have been only for a couple of seconds)

 

Correct. When people refer to solar panels they usually talk about the "panel power rating" (in full midday sunlight in summer), which in my case is 2kWp (the "p" is often added to show it's the peak/panel rating) -- for @Naughty Cal this would be 150W.

 

Energy (not power!) yield per day depends on how long the sun shines for and how brightly, I've been getting 4.4kWh/day which is 2.2x the panel rating -- meaning, it's as if they were in full summer sun for 2.2 hours per day. In summer I'd expect to average 7kWh/day (3.5x the rating), meaning the average light level is equivalent to 3.5 hours of midday sun per day -- more on bright days, less on dull ones.

 

Maximum power reported by the app was 1430W which is 0.7x the panel rating -- as Alan says, probably only for a short time.

 

If NC's panel is 150W and saw the same amount of sunshine as mine, you'd expect a peak output of 150*0.7=105W (measured figure was 110W which is very close) and a yield per day of 150*2.2=330Wh/day -- biggest actual result was about half this (170Wh/day) but a later post said it was only out on full sun for a couple of hours and then parked back in the shade.

 

4 hours ago, Momac said:

The data below from Renology states 100W from a 1.062m x 0.53m panel. That comes to 177W per square metre while the Renology 200W panel is almost exactly 1 square metre .

 A domestic solar installer on the internet claimed more like 150W per square metre which may be more of a real life expectation.

 

 

 

Panel power figures are quoted with 1kW/m2 incident light, so if they're 22% efficient this would mean 220W/m2 *of actual panel area* -- which is not the same as the panel size because of edges/frames, bigger panels lose less due to this.

Edited March 25 by IanD

[MtB]

On 24/03/2024 at 16:48, Naughty Cal said:

Any other ways we can guesstimate it's size?

 

Use a tape measure?

 

It looks to me like about 1200mm x 600mm, which would be about 120W. 

 

Pretty sure my 100W panels are about 1000mmx 600mm (without measuring them!)

[Naughty Cal]

11 hours ago, MtB said:

 

Use a tape measure?

 

It looks to me like about 1200mm x 600mm, which would be about 120W. 

 

Pretty sure my 100W panels are about 1000mmx 600mm (without measuring them!)

Fairly certain it is longer than 1200mm. There isn't half a metre clearance either side to the edge of the roof.