[Guide] Mobile Solar Panels ? . . . - How I Did It -

[Dellmassive]

As above the battery is fully charged...

Drain the battery down and turn on some loads.

The victron watts display will show what you are pulling at that moment..... not the total availible...

So turn some stuff on.

 

[EdH]

As above the battery is fully charged...

Drain the battery down and turn on some loads.

The victron watts display will show what you are pulling at that moment..... not the total availible...

So turn some stuff on.

Aha, just did and it shot up to 70w. So battery will supply power to lights and then PV will replenish/pump power back in to the battery. Every day is a learning day

 

[Dellmassive]

Whats the kit connected too?

Leusure battery under seat?

If so whats running off that battery?..

Or clipped to starter battery under bonnet?

 

[EdH]

Whats the kit connected too?

Leusure battery under seat?

If so whats running off that battery?..

Or clipped to starter battery under bonnet?

I was trying it on my car, wife took the van out for a day I stayed to watch football. Clipped to the cars starter battery.

 

[Dellmassive]

I was trying it on my car, wife took the van out for a day I stayed to watch football. Clipped to the cars starter battery.

Right.... Gotcha.

 

[EdH]

Aha, just did and it shot up to 70w. So battery will supply power to lights and then PV will replenish/pump power back in to the battery. Every day is a learning dayView attachment 119390

@Dellmassive ,

So just to get clear in my head what Victron display indicates.

So, the big circle wattage shows what I am currently drawing/using (69w as per above when I flicked high beams on my Golf). Is this correct.

Then the middle info field which indicates Solar (Voltage and Current). Does this indicates what PV system is producing and charging the battery?

And the last info Battery, indicates current voltage of the battery and the current showing when the consumers are using/running?

I hope you don't mind all these questions, just trying to get my head around all this and to learn more how the system works.

 

[Dellmassive]

@EdH

see below.

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Yes the big circle shows the wattage that is being produced from the solar kit and being delivered to the load (RED)

the figure is delivered from W=V*A from the box bellow.

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The (GREEN) box shows the detailed view of where the Watts ( w=v*a) is coming from.

in your case it shows that your solar panel is developing 17.4V @ 4.0A being produced.

++++

The (YELLOW) box details what the victron MPPT solar controller is doing with the available power - ie outputting as a charger.

you case shows that it is charging the battery in FLOAT mode.

The charge has a multi stage algorithm that will determine the best charge for your battery.

jn this case its charging the battery with a voltage of 12.68v with a current of 5.30A






+++++++++++++++

the way that it works is the sun will generate a voltage on the PV panels.

The MPPT charger will check the battery voltage and decide if it needs charging or not. . .

if NOT then the MPPT will show FLOAT and deliver a very low charge to the battery - the net effect will be that the WATTS will be shown as very low. (even in bright sunshine)(


BUT . . .


If the battery is LOW, or you have a large LOAD running in the van, this will draw a current from the battery . . this in tern will cause a "volt drop" across the battery terminals.

The MPPT will detect the "volt drop" and kick into life, trying to charge the battery back up to FLOAT voltage.

it will do this by converting as much solar PV volts & amps into battery charging volts & AMPS as determine by the MPPT charger algorithm (and user settings) this will give you a bigger WATTS number.

++++


so if you want to see big numbers then you need to run the battery down a bit or run some large loads - like a tyre inflator or similar high current.

if the battery is fully charged you may only see 4W - float,

if the battery is fully charged and you draw 100w for you leisure system - the solar will kick in try to give you that 100w - bulk charge.


+++++


FWIW - when testing setups i like to see what the max i can get out of a setup . .

so i connect a 1000w inverter and run a mains heat gun, 100w lightbulbs etc etc etc . . . . to put a massive load across the battery, this causes a large volt drop accross the battery. - this will intern make the solar setup give out 100%


+++


as a rough guide you can get around 6A per 100w on a good system - theoretical values under test conditions.

realistically you should expect 50-75% of that in the UK depending on sun.


++++

so your 69W look about right.

you might be able to eeek out some more watts by angling the panels so they are perpendicular to the sun.

but . .

the easiest way is to double up the panels. . so two of your panels should gwt you 69w + 69w = 138W


.

 

[mmi]

Pictured from a slightly different perspective - still the same numbers and colours.

Thus also actual/residual battery current is unknown when unmetered load/consumers are on.

 

[Nigel W]

Big thankyou to @Dellmassive I have just ordered the Renology panel he recommended which after using the discount code he provided worked out at £135 delivered.
I will hold off buying a fancy controller as the one that comes with it is, they say, waterproof and sounds as if it will do the job so time will tell.
Hopefully getting it connected will be a simple job now I know, or think I know, what extra connectors to get - wish me luck!

 

[Dellmassive]

@Nigel W

Your welcome.

For everyone else.... here is your 10% discount code.

I can get you a discount at Renogy United Kingdom

Hey, if you're ever looking for Renogy United Kingdom products, let me know and I can get you a discount at Renogy United Kingdom. Here's a coupon if you need one now:

renogyuk.refr.cc

...

 

[Dellmassive]

here is another nice example from the Victron readout. (of how the solar system works and how the power flows)

from the solar shed project - https://www.t6forum.com/threads/solar-sheds-other-non-t6-solar-projects-how-we-done-it.16457/

today June 2021, early atm so low solar, but still 100W, its showing:

101W being generated by the Panels.
80W charging the battery.
20W running loads.

so 100W=80+20W





..
here is the MPPT view:



and the smart BMV view:




...


this is the same data, but from the VRM Portal online.





here is another screen shot - later in the day.


147W from panel,

battery fully charged so only 11w to battery for float.

136W out to loads.






.

 

[Big.mac]

I thought it might be helpful to add some screenshots from the Renogy app just as an alternative to the Victron stuff. I have a Renogy DCC30S DC-DC charger with MPPT and the Bluetooth module which allows connecting to your phone running this little app.

First picture shows van in fully charged status. Both batteries being trickle charged from solar. Low current output from panel and low amps into each battery. Panel is 180watts, pretty well in full sun.
N.B. Top section is panel output except power which is for some reason the power into the (leisure) battery.
middle section is leisure battery (13.8V 0.51A)
bottom section is starter battery (13.3V 0.27A)



You can see the voltage at the same time on the BM2 monitors:


Next view is after I unlocked the van and opened the tailgate so systems start up and interior lights come on etc.
Amps out of panel increase and are pushed into starter battery which now has a load on it. Leisure battery remains in trickle mode (and the load is unchanged).


I then opened the fridge (which is connected to the leisure battery) to get it to start the compressor. Solar amps increase as MPPT pushes amps into both starter and leisure batteries:


So in total I get 100watts of power out of the panel when I add some load. Could I get a bit more, i don’t know TBH as I’ve not tested it with any higher load than this. My goal was to be able to run my fridge for multi day trips completely from solar. I can do this so I’m happy with it.

Final picture below is the leisure battery when the van was parked up all day while we were out walking in the mountains. Can’t really say for sure what the weather was like in the campsite but it was absolutely p***ing down up on the hill. Site was dry when we returned but I’d guess mixed levels of sunshine. You can see where the fridge kicks in as all the downward spikes and you can almost predict daylight hours based on the voltage curve.

If you’ve to one of the Renogy DC-DC units the Bluetooth module is a useful addition for not much money.

 

[AK06FR]

Has anyone (AKA @Dellmassive ) noticed a drop off in their panel outputs now its summer ? I live in the South of France and it been sunny 28Deg all weekend, I was expecting to see high wattage out of my portable panel - rated 120W. The maximum I've seen is around 80W. A month or so back with the temperature of 20Deg I was getting 110W plus.

Adam

 

[Dellmassive]

yes . . . to a degree.


++++

heat can reduce output efficiency by 10-25%

but COLD can also effect things:

Cold can increase output efficiency by 10-25%


Victron mention this when sizing panels and leaving headroom on the controller for cold sunny conditions - ie The Alps.


++++

panel ratings are set at standard test conditions.

as an example this 100W Lensun - Lensun® 100W 12V ETFE Black Flexible Solar Panel with Fiberglass Back Sheet is Stronger than the Cheap White PET backsheet





Electrical Information:

Peak power: 100W
Solar cell efficiency: 22%
Maximum power voltage: 18V
Maximum power current: 5.56A
Open circuit voltage: 21.24V
Short circuit current: 6.11A
Power allowance range: +/-3%
Maximum system voltage: 500V
Values at standard test conditions: Air Mass - AM1.5, Irradiance - 1000W/m2, Cell Temperature - 25°C


++++++

25degC is that standard test temperature.


as the temp of the panel rises the output will drop down a bit

as the temp does down the PV voltage will rise.

+++++

more info: How Does Heat Affect Solar Panel Efficiencies?


It may seem counter-intuitive, but solar panel efficiency is affected negatively by temperature increases. Photovoltaic modules are tested at a temperature of 25 degrees C (STC) – about 77 degrees F., and depending on their installed location, heat can reduce output efficiency by 10-25%. As the temperature of the solar panel increases, its output current increases exponentially, while the voltage output is reduced linearly. In fact, the voltage reduction is so predictable, that it can be used to accurately measure temperature.

.

Determining Your Efficiency​

The best way to determine your panel’s tolerance to heat is by looking at the manufacturer’s data sheet. There, you’ll see a term called the “temperature coefficient (Pmax.)” This is the maximum power temperature coefficient. It tells you how much power the panel will lose when the temperature rises by 1°C above 25°C. @ STC (STC is the Standard Test Condition temperature where the module’s nameplate power is determined).

For example, the temperature coefficient of a solar panel might be -.258% per 1 degree Celsius. So, for every degree above 25°C, the maximum power of the solar panel falls by .258%, for every degree below, it increases by .258%. What this means no matter where you are, your panel may be affected by seasonal variations. However, the temperature coefficient also tells you that efficiency increases in temperatures lower than 25°C. So, in most climates, the efficiency will balance out over the long run.

For a geographic region where temperatures higher than 25 degrees C. are the norm, one can consider alternatives to Mono or Polycrystalline modules, which have the highest efficiency (At 1:1 concentration), but also the highest temperature coefficient at PMAX. Project designers may want to consider a thin film or CdTe module – or in the case of a very large project, High Concentration PV, which is designed for hot climates, but not applicable for small projects.



++++

rough example:

 

[AK06FR]

Thanks @Dellmassive interesting reading.

A good excuse to make a sortie to the Alps this weekend for some altitude / cooler temperature solar testing.

 

[Dellmassive]

yeh . . .

Youtuber Will P . . . done some tests using a hose pipe and water squirty bottle to drop the cell temps. (spraying the panels)

The PV volts jumped up - - - then back down and settled again as the panel temp stabilised.

i normally go for a 50% - 75% expectancy of the panel rating.

so 50w-75w per 100W.

if you NEED that 100w . . . . then double up on panels.


ie 200W worth of panels will defo give you the 100W you want.

if you have a roof mount already - then just add in a mobile panel.

 

[AK06FR]

yeh . . .

Youtuber Will P . . . done some tests using a hose pipe and water squirty bottle to drop the cell temps. (spraying the panels)

The PV volts jumped up - - - then back down and settled again as the panel temp stabilised.

i normally go for a 50% - 75% expectancy of the panel rating.

so 50w-75w per 100W.

if you NEED that 100w . . . . then double up on panels.


ie 200W worth of panels will defo give you the 100W you want.

if you have a roof mount already - then just add in a mobile panel.

Yes that ratio looks about right, I've been running the 120W panel all weekend via a PowerOak PS6 cooling my beers in a Dometic CFX35. Chasing the sun around the garden I'd say I'm seeing on average around 65 - 75W. At 19:45h I see around 25W which is still ok imo.

I'm using this panel:-

Voltero | Voltero S120 120W 18V solar panel with SunPower cells

The S120 zone panel is available, strong, lightweight and flexible. The S120 panel has a capacity of 120 watts and is made of semi-flexible plastic...

poweroak.eu

I was thinking or running a second panel, maybe getting a larger 200W panel to charge the PS6 faster. What the score having differing panel ratings series or parallel for the best results.

Cheers

Adam

 

[Dellmassive]

its best to match the panels as close as possible,

preferably double up with the same panels.


similar wattage panels are normally very close spec wise . . . eg 120w + 120W = (120w+120W)



with multiple panels its easiest to just down-rate all panels to the weakest link. - then add up like normal. - eg 150w + 120W = (120w+120W)

eg . .

[Guide] Mobile Solar Panels ? . . . - How I Did It -

Mobile Solar Panels ? . . . - How I Did It - There is loads of background to this . . . . . but for now here is a vid for you all. =] Just remember W = V*A and as a general rule a good 100W panel will give you up to 6A charge with good sun. 25w = 1.5A 50W = 3A 100w = 6A 200w = 12A 300w = 18A...

www.t6forum.com

.

 

[AK06FR]

its best to match the panels as close as possible,

preferably double up with the same panels.


similar wattage panels are normally very close spec wise . . . eg 120w + 120W = (120w+120W)



with multiple panels its easiest to just down-rate all panels to the weakest link. - then add up like normal. - eg 150w + 120W = (120w+120W)

eg . .


View attachment 119679View attachment 119680

[Guide] Mobile Solar Panels ? . . . - How I Did It -

Mobile Solar Panels ? . . . - How I Did It - There is loads of background to this . . . . . but for now here is a vid for you all. =] Just remember W = V*A and as a general rule a good 100W panel will give you up to 6A charge with good sun. 25w = 1.5A 50W = 3A 100w = 6A 200w = 12A 300w = 18A...

www.t6forum.com

.

Cheers and sorry for you having to repeat yourself. Iwas just reading your earlier posts on the subject, I just start at post #1 in the future !!

 

[YannMcHaggis]

Dellmassive please can I tap into your seriously impressive knowledge for some advice?!

My converter has fitted an MPPT charge controller for me so I can use mobile panels, it's this one (PV Logic MPPT Pro). This is rated to 15A, and in various places I've seen it saying it can take anywhere from 180W to 225W.

I've just ordered the Lensun 200W solar blanket, is this going to be ok to use with my charge controller, or is it too close to the top end of its rating and would I be safer with a lower output panel? Thanks!