Multiple solar panels to a common bus bar?

[Hoohaa]

Originally Posted by Wotname

This panel don't look like a 350W panel to me. It is also a low voltage panel (nominally 12V) - not good.
1. No power stated on specification label - red flag.
2. Only .923 sq M - big red flag
3. No current stated on specification label - red flag

Do you have any other data about the panel e.g model number or sales brochure etc?

FWIW, here is a typical spec for a proper 330W panel (just one I found at random but it is a reasonable quality panel.
Especially compare the panel area which is a good start on how much power you might expect.

https://www.phonosolar.com.au/wp-con...-330W-2020.pdf

Here's the link to the panel's I bought.
https://www.ebay.com.au/itm/273957360400
I did think it was a bit suss when they don't even quote the wattages on the label.

[Uncle Bob]

Originally Posted by Hoohaa

Here's the link to the panel's I bought.
https://www.ebay.com.au/itm/273957360400
I did think it was a bit suss when they don't even quote the wattages on the label.

Perhaps it's time to see how good this is.

https://www.cruisersforum.com/forums...1&d=1668038352

lifted from the fleabay add you linked.

[Hoohaa]

Yeah. I was thinking that.
When first looking at these, I thought that panel technology must have advanced in order to produce more watts per square meters.
Come in sucker.
I would like to know how to calc the actual wattage of these panels. I did see over 300watts a couple of days ago so they must be North of 150.
I'll wait for a bit more info before I contact the supplier.

[RaymondR]

Originally Posted by Hoohaa

Yeah. I was thinking that.
When first looking at these, I thought that panel technology must have advanced in order to produce more watts per square meters.
Come in sucker.
I would like to know how to calc the actual wattage of these panels. I did see over 300watts a couple of days ago so they must be North of 150.
I'll wait for a bit more info before I contact the supplier.

Variable resistance shunt (SS pushbike spoke and two alligator clamps) across the output and increase the resistance until the simultaneous product of the voltage and current is maximized.

[Hoohaa]

Originally Posted by RaymondR

Variable resistance shunt (SS pushbike spoke and two alligator clamps) across the output and increase the resistance until the simultaneous product of the voltage and current is maximized.

Still trying to get my head around this one.
Correct me if I'm wrong but you want me to wire up a panel 2 a bicycle spoke and move the wiring along the spoke until I get equal voltage and current?
Are there any YouTube videos showing this technique or something similar?

[Mike OReilly]

Originally Posted by Wotname

This panel don't look like a 350W panel to me. It is also a low voltage panel (nominally 12V) - not good.
1. No power stated on specification label - red flag.
2. Only .923 sq M - big red flag
3. No current stated on specification label - red flag

Agreed. I don't know what you've got, but it sure doesn't look like a 350 watt panel.

[RaymondR]

Originally Posted by Hoohaa

Still trying to get my head around this one.
Correct me if I'm wrong but you want me to wire up a panel 2 a bicycle spoke and move the wiring along the spoke until I get equal voltage and current?
Are there any YouTube videos showing this technique or something similar?

Maximize the product of the voltage multiplied by the current and the result is the wattage produced with the extant amount of sunlight. You probably would not get the full nameplate wattage of the panel but on a nice sunny day around mid day it should be in the ballpark.

[Pete7]

Originally Posted by Wotname

This panel don't look like a 350W panel to me. It is also a low voltage panel (nominally 12V) - not good.
1. No power stated on specification label - red flag.
2. Only .923 sq M - big red flag
3. No current stated on specification label - red flag

Our 300w panels are 1 x 1.5 SqM and have an efficiency of 19.6% so not bad. Sadly 1.3 x 0.7 Sqm suggests a 150w panel.

Suggest Hoohaa asks for a refund. The UK e bay site is currently littered with panels that aren't even close to producing the claimed power output. They are mainly semi flexible and sold directly from China. Its like they don't care and hope most buyers won't bother sending them back.

Pete

[Pete7]

Originally Posted by Hoohaa

Yeah. I was thinking that.
When first looking at these, I thought that panel technology must have advanced in order to produce more watts per square meters.

Are the solar panels under that top row of stainless steel tubes? That and the wind mill will also have an impact on the amount of power being generated by casting shadows.

Pete

[Hoohaa]

Originally Posted by Pete7

Are the solar panels under that top row of stainless steel tubes? That and the wind mill will also have an impact on the amount of power being generated by casting shadows.

Pete

Yes and no
The panels are not under the cross bars. Future project is to elevate them to the cross bars.
The wind gen always casts shadows but I just live with it.
The current setup is kicking _ss. I'm fully charged and on float at around 1 pm.. My bank is 855 AH.
So all in all, I'm pretty happy with it. But! That doesn't mean that I'm going to let this rest.
The supplier is here in Sydney. I haven't contacted him yet but will get my ducks in a row first.
The biggest cost has been the upgraded Victron MPPT so that I can handle all of the imaginary extra amps.
What I need to do is figure out what I actually have (wattage).

[Wotname]

OK, those panel figures are at the best, aspirational but perhaps better put, bull-dust.

Let’s go back to basics: the total power you will get is dependant on the area of the panel; it’s efficiency and the amount of solar radiation you are receiving on the day. The area of the panel is fixed; the efficiency varies with temperature (and to some extent, the amount of radiation); the solar radiation is dependant on location, time of day, and atmospheric conditions (cloud cover, dust etc).

From Wikipedia - https://en.wikipedia.org/wiki/Solar_irradiance Average annual solar radiation arriving at the top of the Earth's atmosphere is roughly 1361*W/m2. The Sun's rays are attenuated as they pass through the atmosphere, leaving maximum normal surface irradiance at approximately 1000*W/m2 at sea level on a clear day.

Usually panel data is calculated on this figure of 1000 W/m2 with a temperature of 20C. While we don’t know how the data of these dodgy panels are specified, we can still run some numbers. Panel area is claimed to be 0.931 m2 but I think they are including the frame and the gaps between the cells, still let’s give them the benefit of the doubt and call it .93 m2. Claimed efficiency is 24% (this is very high and also suspect) but let’s use it. So max power will be 1000W x .931 x 24% which equals 223.2W. The only way to get 350W from this panel is if the solar radiation is 1,568 W/m2 and that is never going to happen until the earth moves much closer to the sun.

However I think the real figure for this panel is more likely to around 170 W. I am using an area of .9 m2 and an efficiency of 17%. Remember these numbers are predicated on 1000 W/m2 and 20C. What is the actual numbers for solar radiation in Sydney? These guys https://en.tutiempo.net/solar-radiation/sydney.html suggest it peaked today (at 1300) with 889 W/m2 so I think the very best you could have expected would have been 150 W at 1300 and 120 W two hours either side of that - assuming it was sunny and the panel was pointing directly towards the sun.

EDIT - the temperatures mentioned above should have been 25C.

[Uncle Bob]

Originally Posted by Hoohaa

Yes and no
The panels are not under the cross bars. Future project is to elevate them to the cross bars.
The wind gen always casts shadows but I just live with it.
The current setup is kicking _ss. I'm fully charged and on float at around 1 pm.. My bank is 855 AH.
So all in all, I'm pretty happy with it. But! That doesn't mean that I'm going to let this rest.
The supplier is here in Sydney. I haven't contacted him yet but will get my ducks in a row first.
The biggest cost has been the upgraded Victron MPPT so that I can handle all of the imaginary extra amps.
What I need to do is figure out what I actually have (wattage).

Jeff, I reckon you should return (or attempt to) those panels promptly, the longer you leave it the harder it will become, and buy from a better supplier, one with a lower BS factor. I have been happy with a melbourne retailer, Low Energy Developments and can recommend them from experience. They are contactable by phone and don't speak chinglish.

[Wotname]

Originally Posted by Hoohaa

...........
The biggest cost has been the upgraded Victron MPPT so that I can handle all of the imaginary extra amps.
What I need to do is figure out what I actually have (wattage).

The Victron MPPT works best with 'high voltage house panels' and the panels you have are 'low voltage 12V' panels. In low light conditions (early morning etc), the output voltage of a nominal 12V panel is often too low for the Victron and it won't kick in until the panel voltage rises later in the day.

[RaymondR]

Originally Posted by Wotname

The Victron MPPT works best with 'high voltage house panels' and the panels you have are 'low voltage 12V' panels. In low light conditions (early morning etc), the output voltage of a nominal 12V panel is often too low for the Victron and it won't kick in until the panel voltage rises later in the day.

Which is why you need to wire the panels in series.

My Victron MPPT is a 150/60 which means I could put say eight 12V panels in series and stay under the 150 volt input limit (lovely small wiring since the amps are low) into the input and take a maximum of 60 amps from the output. The controller is mounted about 2' from the battery, which requires a short run of big cables, and 15' from the panels, a longer run of smaller cables.

[Wotname]

Originally Posted by RaymondR

Which is why you need to wire the panels in series.

My Victron MPPT is a 150/60 which means I could put say eight 12V panels in series and stay under the 150 volt input limit (lovely small wiring since the amps are low) into the input and take a maximum of 60 amps from the output. The controller is mounted about 2' from the battery, which requires a short run of big cables, and 15' from the panels, a longer run of smaller cables.

If you are using nominal 12V panels, then yes, the Victron MPPT works better if the panels are wired in series. The downside is of course, more potential shading problems. If one panel is shaded, they all stop producing power.

IMHO a better alternative is to use 'house' panels which has output voltages fro about 20V to 40V. Of course getting small area sub 300W house panels is difficult if not impossible.