Solar Panel kit out - a summary (1 Viewer)

[Weimarunner]

I'm considering a single panel for the roof of my campervan. I've been reading lots of posts on here about the considerations to be made and so far I've deduced the following. It'll be great to hear your thoughts, I've not ordered anything as yet.

• Panel size / wattage - as big/powerful as the available space allows. Better to be overpowered rather than under.
• Solid panel with corner brackets rather than flexible.
• Monocrystaline rather than Polycrystaline for better efficiency when overcast
• No real benefit of an MPPT controller on smaller (100-120w) systems, so PWM controller best bet

If the above is a fair summary, this kit seems to fit the bill, how would you rate it? - http://www.ebay.co.uk/itm/100W-mono...472718?hash=item43cd42240e:g:DGUAAOSw4hdXIQ9K

Thanks in advance
Pete

 

[bigtree]

This is on the same page as your ad further down and cheaper.

http://www.ebay.co.uk/itm/100W-sola...1648863&pid=100005&rk=2&rkt=6&sd=291206472718

 

[tonka]

Mono v Poly both have their advantages and in practice with just a single panel not worth worrying about.

MPPT as you say not critical based on system size...

Based on the two criteria above, If you were that fussy then another battery would be a better way to invest the cash.
You can overspec things, spend more and get very little in return.

Kit looks fine.. You could shop about and get more watts for a cheaper spend.
This is where I (and a few others) have had last panels from..
http://www.friendlygreengiant.com/index.php?route=product/product&path=25&product_id=34

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[Weimarunner]

This is on the same page as your ad further down and cheaper.

Thanks BT. Looking at the pics of the controller in that ad, is that for just a single battery set up? I want to charge both cranking and leisure batteries.

 

[mitzimad]

you need either a two channel controller or fit a batter masters as well

 

[bigtree]

Thanks BT. Looking at the pics of the controller in that ad, is that for just a single battery set up? I want to charge both cranking and leisure batteries.

Looks just the same connections as your link.

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[Weimarunner]

Mono v Poly both have their advantages and in practice with just a single panel not worth worrying about.

MPPT as you say not critical based on system size...

Based on the two criteria above, If you were that fussy then another battery would be a better way to invest the cash.
You can overspec things, spend more and get very little in return.

Kit looks fine.. You could shop about and get more watts for a cheaper spend.
This is where I (and a few others) have had last panels from..
http://www.friendlygreengiant.com/index.php?route=product/product&path=25&product_id=34

Hi Tonka,
Thanks for the link, they look very reasonable prices.
I've not really read in to the difference between the panel types but did read the Ppoly panels didn't charge in overcast conditions, so given the UK weather I instantly edged towards mono.
When you say an additional battery, I already have a starter and leisure battery, do you mean a 2nd leisure battery?

 

[Weimarunner]

you need either a two channel controller or fit a batter masters as well

Thanks MM

 

[iceclimber]

This is where I (and a few others) have had last panels from..
http://www.friendlygreengiant.com/index.php?route=product/product&path=25&product_id=34

these look a fair price ....... I need a 2nd panel on the roof as am pretty sure the single existing one is only 80 (ish) watts & I would guess that its around 8 / 10 years old now (Ive had the van 4 years)

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[Camping Gaza]

You will get very little charge in winter in the UK, mono or poly, one dark overcast sky and nowt nix nada, but with a little watery sun or a bright day may give you a little to keep them batteries floating. If you were at the equator mid summer no clouds you will get 4 to 5 amps 90 degrees to the suns rays.

Theres a few dual battery chargers on ebay, so you can set them to what and when it charges.

I got 300 watts on my roof. In sunlight I get a good few amps but not much in winter.

I got mine from friendly green giant and they do a good service, and are about the cheapest.

 

[Weimarunner]

Thanks CG, that's a good insight.
The friendly green giant site doesn't give a lot of details on their panels ?

 

[tonka]

Hi Tonka,
Thanks for the link, they look very reasonable prices.
I've not really read in to the difference between the panel types but did read the Ppoly panels didn't charge in overcast conditions, so given the UK weather I instantly edged towards mono.
When you say an additional battery, I already have a starter and leisure battery, do you mean a 2nd leisure battery?

Yes... The best option even before solar is a second leisure battery. You instantly double your capacity and often the cheaper option. Once you have that then at least the solar can store more as well.
Not sure where you read about Poly not charging in overcast, mine certainly does and I have had several over the years..
Mono are meant to be better, so it's down to cost and size really.

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[tonka]

Thanks CG, that's a good insight.
The friendly green giant site doesn't give a lot of details on their panels ?

All I can state is they have been around a while and i know several other funsters who have bought and never heard a bad word about service or quality. Just offering as a price comparison.

 

[hilldweller]

If the above is a fair summary, this kit seems to fit the bill,

Pete

Looks good to me. Similar to ours which has served well for 5 years now.

 

[Lenny HB]

If you are using the van through the winter well worth buying a good MPPT regulator allows you to squeeze every last drop of power in low light conditions.

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[funflair]

Im with Lenny on the "fit a decent MPPT reg" I don't understand the argument that it isn't worth it on a smaller set up, 25% to 30% extra from your panel no matter what size must be worth going for in my book.

Martin

 

[tonyidle]

All this also depends on your needs. Mine are for one period of three weeks per year when I'm on three different sites during that time none of which have EHU available. On any other trip, other than the odd night or two, I'll use sites with EHU. I have two batteries total capacity around 200Ah and I have three panels on the roof, all bought / acquired at different times, totalling 230W and with an MPPT regulator. I do not use an inverter. That combination gives me at least three weeks during August / September in the UK. It would go on longer if I needed it to as long as it was during June to September. If I was offering advice to someone uncertain as to their future needs it's simple: the largest battery capacity and as much solar as will fit the available space and not frighten the wallet.

 

[Weimarunner]

Yes... The best option even before solar is a second leisure battery. You instantly double your capacity and often the cheaper option. Once you have that then at least the solar can store more as well.
Not sure where you read about Poly not charging in overcast, mine certainly does and I have had several over the years..
Mono are meant to be better, so it's down to cost and size really.

Thanks Tonka, that's a good tip and makes perfect sense to add the 2nd leisure battery. I suppose you can still use a dual battery solar controller but wire the two leisure batteries in line?

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[Weimarunner]

Im with Lenny on the "fit a decent MPPT reg" I don't understand the argument that it isn't worth it on a smaller set up, 25% to 30% extra from your panel no matter what size must be worth going for in my book.

Martin

Thanks Martin, yes I don't understand either. I don't mind paying more for the MPPT controller to squeeze a few percent more power but all the manufacturers and solar specialists seem to recommend PWM for smaller panel set ups. This is what Photonic Universe say about MPPT -
" MPPT controllers are the most efficient and powerful controllers that we offer, but they should only be used when the solar panel voltage is much higher than the battery voltage. An MPPT system is able to lower the voltage of a panel (or an array of solar panels) that is up to ten times higher than the voltage of a battery to match the voltage of the battery without losing any of the current in the process.
There would be no negative repercussions from using a MPPT controller on a solar panel with a voltage close to the battery voltage, but the benefits from MPPT in this sort of system would be much lower.

It has the same protective features as the PWM controllers. We include a 20A MPPT controller in our 200W/250W kits, due to the fact that an MPPT controller allows the panel to operate at the maximum level that it can. Some have built-in LCD displays, while others have RJ45 sockets for a remote meter that allow you to monitor the charging process."

 

[Lenny HB]

Thanks Martin, yes I don't understand either. I don't mind paying more for the MPPT controller to squeeze a few percent more power but all the manufacturers and solar specialists seem to recommend PWM for smaller panel set ups. This is what Photonic Universe say about MPPT -
" MPPT controllers are the most efficient and powerful controllers that we offer, but they should only be used when the solar panel voltage is much higher than the battery voltage. An MPPT system is able to lower the voltage of a panel (or an array of solar panels) that is up to ten times higher than the voltage of a battery to match the voltage of the battery without losing any of the current in the process.
There would be no negative repercussions from using a MPPT controller on a solar panel with a voltage close to the battery voltage, but the benefits from MPPT in this sort of system would be much lower.

It has the same protective features as the PWM controllers. We include a 20A MPPT controller in our 200W/250W kits, due to the fact that an MPPT controller allows the panel to operate at the maximum level that it can. Some have built-in LCD displays, while others have RJ45 sockets for a remote meter that allow you to monitor the charging process."

That sounds Irish to me, I think that blurb is talking about larger domestic type installations.
The reason for using an MPPT regulator is the opposite of what they say, it is when the output is low and only slightly above the battery voltage is when you gain from an MPPT regulator turning what few volts that are avalable into useful power to charge your batteries.

 

[funflair]

Thanks Martin, yes I don't understand either. I don't mind paying more for the MPPT controller to squeeze a few percent more power but all the manufacturers and solar specialists seem to recommend PWM for smaller panel set ups. This is what Photonic Universe say about MPPT -
" MPPT controllers are the most efficient and powerful controllers that we offer, but they should only be used when the solar panel voltage is much higher than the battery voltage. An MPPT system is able to lower the voltage of a panel (or an array of solar panels) that is up to ten times higher than the voltage of a battery to match the voltage of the battery without losing any of the current in the process.
There would be no negative repercussions from using a MPPT controller on a solar panel with a voltage close to the battery voltage, but the benefits from MPPT in this sort of system would be much lower.

It has the same protective features as the PWM controllers. We include a 20A MPPT controller in our 200W/250W kits, due to the fact that an MPPT controller allows the panel to operate at the maximum level that it can. Some have built-in LCD displays, while others have RJ45 sockets for a remote meter that allow you to monitor the charging process."

Well my experience is as follows:

We bought the van and it already had one 80 watt solar panel, PWM regulator and Fox display, I then fitted 3 more 80 watt panels and a Votronic MPP regulator and solar computer, So I could now watch the output from the panels and the single panel always made 25% to 30% less pro rata compared to the other 3, So I bought another Votronic MPP and fitted this to the single panel and again watched the output and "hey presto" it now tracked the other 3 on a pro rata basis.

In conclusion although not terribly scientific, I think they do what they claim on the box.

Martin

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[TheCaller]

This is what Photonic Universe say about MPPT -
" MPPT controllers are the most efficient and powerful controllers that we offer, but they should only be used when the solar panel voltage is much higher than the battery voltage. An MPPT system is able to lower the voltage of a panel (or an array of solar panels) that is up to ten times higher than the voltage of a battery to match the voltage of the battery without losing any of the current in the process.
There would be no negative repercussions from using a MPPT controller on a solar panel with a voltage close to the battery voltage, but the benefits from MPPT in this sort of system would be much lower.

A single solar panel will produce an output at around 21v in full sun. A battery requires a charging voltage of around 13v before anything starts going in & shouldn't be charged at more than around 15v at any time, falling off as it gets nearer to full charge.

So as daylight creeps over the horizon, the panel output starts to rise from 0v in darkness & eventually passes the 13v level at which point current starts to flow into the battery. It then passes the 15v (approx) point, at which point the PWM controller effectively throws away the extra potential by limiting, or pulsing the charge going to the battery. Don't ask me to explain exactly how pulse width modulation works, because I don't know, but there is a clue in the name. A PWM controller can only cope with a maximum panel output voltage of about 25v, so if you have more than one panel, you must wire them is parallel so the voltage never goes up, even though the current will. You will always be throwing away the same percentage of the available power though, so the more panels, the more wasted power in full sun.

Again, don't ask me to explain how it does it, but a MPPT controller can convert a higher voltage coming from the panels into usable current at the voltage that the battery wants. So less wastage. But there is another advantage that I think is partly what Photonic Universe are getting at in their quote above. Because an MPPT controller can handle a higher voltage from the panels, you can now connect panels together in series. So two panels now output 42v in full sun rather than 21v. So as the sun starts to rise in the morning, the voltage passes the 13v point at which the batteries start to charge much sooner. On a dull winter's day in the UK, that can make the difference between getting a trickle charge to keep your batteries topped up & getting nothing at all, because your panel(s) individually may never make it above 13v.

The panel output power is the same in both cases, but the MPPT controller makes better use of it. As the limiting factor on a motorhome is roof space & possibly weight, then as you approach either of those limits, making best use of the potential output becomes more important.

 

[Reallyretired]

Absolutely agree with the above. Even a sigle panel on its own will produce a voltage over 20v if there is sunshine. Mine were producing 21v yesterday in UK which is not bad for beginning of March so MPPT controller is still worthwhile even with one panel.
MPPT controllers are generally quite a bit larger and heavier than PWM as well as more expensive.
An extra battery is great but weighs 20kg+ where a solar panel is around 7-8kg

 

[Weimarunner]

FF,TC & RR - many thanks, I'm sold on a MPPT controller. Will amend the summary. Thanks again

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[Neckender]

A single solar panel will produce an output at around 21v in full sun. A battery requires a charging voltage of around 13v before anything starts going in & shouldn't be charged at more than around 15v at any time, falling off as it gets nearer to full charge.

So as daylight creeps over the horizon, the panel output starts to rise from 0v in darkness & eventually passes the 13v level at which point current starts to flow into the battery. It then passes the 15v (approx) point, at which point the PWM controller effectively throws away the extra potential by limiting, or pulsing the charge going to the battery. Don't ask me to explain exactly how pulse width modulation works, because I don't know, but there is a clue in the name. A PWM controller can only cope with a maximum panel output voltage of about 25v, so if you have more than one panel, you must wire them is parallel so the voltage never goes up, even though the current will. You will always be throwing away the same percentage of the available power though, so the more panels, the more wasted power in full sun.

Again, don't ask me to explain how it does it, but a MPPT controller can convert a higher voltage coming from the panels into usable current at the voltage that the battery wants. So less wastage. But there is another advantage that I think is partly what Photonic Universe are getting at in their quote above. Because an MPPT controller can handle a higher voltage from the panels, you can now connect panels together in series. So two panels now output 42v in full sun rather than 21v. So as the sun starts to rise in the morning, the voltage passes the 13v point at which the batteries start to charge much sooner. On a dull winter's day in the UK, that can make the difference between getting a trickle charge to keep your batteries topped up & getting nothing at all, because your panel(s) individually may never make it above 13v.

The panel output power is the same in both cases, but the MPPT controller makes better use of it. As the limiting factor on a motorhome is roof space & possibly weight, then as you approach either of those limits, making best use of the potential output becomes more important.

@TheCaller So what you are saying is on my install when the van arrives I can connect my 2 100 watt semi flexible panels in series to the Schaudt LRM1218 MPP regulator and this will be more efficient than connecting them in parallel.

John.

 

[Lenny HB]

The LRM1218 is not suitable for panels in series it has a max input voltage of 32v.
On a Motorhome panels wired in series is not a good idea. If you get shade on one panel you will loose most of your output where as if wired in parallel if one panel is in shade you will still get the output from the other panel.

 

[TheCaller]

@TheCaller So what you are saying is on my install when the van arrives I can connect my 2 100 watt semi flexible panels in series to the Schaudt LRM1218 MPP regulator and this will be more efficient than connecting them in parallel.

John.

What @Lenny HB said about the LRM1218. Unusually for a MPPT controller, it isn't designed to handle the voltage of panels wired in series.

As to whether the shading outweighs the better performance on dull days, well that all depends on where you park it.
(& on whether you have any sticky-up bits on your roof that might cast a shadow)

There is no one right answer with solar. So much depends on when, where & how you use your van.

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[Gromett]

Series is better under optimal conditions if your charge controller supports it. HOWEVER, if one of your panels gets shaded you will lose the total energy from both panels.
If they are wired in parallel you will only lose power from the one panel that is shaded.

If in series you therefore have to make sure you are not near any shaded areas such as trees etc.

 

[Neckender]

Thanks lads I'll be wiring in parallel as I've always done,

John.

 

[Weimarunner]

Absolutely agree with the above. Even a sigle panel on its own will produce a voltage over 20v if there is sunshine. Mine were producing 21v yesterday in UK which is not bad for beginning of March so MPPT controller is still worthwhile even with one panel.
MPPT controllers are generally quite a bit larger and heavier than PWM as well as more expensive.
An extra battery is great but weighs 20kg+ where a solar panel is around 7-8kg

Hi all,
Just started to talk through my requirements with a supplier. I opted for all top quality, high output components based around the maximum size panel (100w) I can fit on my roof and a dual battery MTTP controller . The owner of Photonic Universe had this to say -

" Regarding the controller, yes, this is the one we would recommend. There is no large benefit to an MPPT controller given the voltage of this panel (the maximum voltage of 17.5is not sufficiently above the battery charging
voltage to gain much in terms of amps). If you had said the 200W rigid panel, or even the 140W semi-flexible, then an MPPT controller would be recommended. I know some companies always try to sell the more expensive MPPT type when it isn't really that beneficial."

Just thought this was interesting and backs up why 100w & smaller panel kits are usually paired with PWM controllers?

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