Solar The Solar Panel Thread

[Boots in Action]

Continuing on from my above post(two solar panels controlled by seperate controllers to 2 batteries in parallel)
Would I benifit from two identical controllers? I already have a StecaPR2020, would it be better to purchase another one of these or would any decent PWM controller do.
Or simply buy 2 new MPPT controllers?

Hi @Moto Mech , are you still going to use the flexi panels or use the 2 X 120W panels?? If going to use the framed panels, go for just the one MPPT controller if you can afford it and there is a need for such outlay. Connected in series will give you heaps!! If still going to use the thin panels and can get some cooling air around the back of the panels, you still might get away with it. The choice is yours. Using one good solar controller IS the way to go, but I understand your issues after bad experiences. Sometimes one has to accept compromises when the ultimate cannot be achieved. Obviously, it would be better to have two controllers of same type and identical because the chances are that there will be little variance in operation. Seems an expensive way to do it, but for the purist worth it. But I am like @mikerezny , I hate spending money unnecessarily on just a whim. I have to have a real need and a high expectation of a worthwhile improvement!!

 

[Boots in Action]

Im installing them in series and I read the same thing on an eBay flexi panels listing, so I queried it with them and the broken english that came back seem to suggest that was an issue not applicable to the current panels. That could be just to appease a potential buyer. I also touched base with a bricks and mortar RV solar supplier here in Vic (solar4rvs.com.au) that deals in flexis, and they never mentioned anything adverse about heat in their reply

Many of the ebay listings sell them in multi panel sets anyway.

We're right on the vans weight limit, so Im going to give the flexi's a go. Im not buying another controller in any regard, so Ill see how the flexi's go.
The Greca profile polycarb is 16-29mm high, and the Trimdek profile 26mm, so Im hoping that's enough to give them some breathing space. I could double up the polycarb but I'd have to check the weight first so double sheeting doesnt defeat any weight saving

Hi @Crusty181 , sounds like the later thin panels are less affected by heat and your air space underneath will certainly help. Another thing that came to mind about heat buildup was the necessity to keep the surfaces clean. Dirt and dust layers on the panels which are nearly flat would certainly NOT be a help as it would retain the heat on the surface of the panels. Possible?? Your success or otherwise with slim panels will be useful for other members on this forum. Looking forward to how you go. Good luck.

 

[mikerezny]

Im installing them in series and I read the same thing on an eBay flexi panels listing, so I queried it with them and the broken english that came back seem to suggest that was an issue not applicable to the current panels. That could be just to appease a potential buyer. I also touched base with a bricks and mortar RV solar supplier here in Vic (solar4rvs.com.au) that deals in flexis, and they never mentioned anything adverse about heat in their reply

Many of the ebay listings sell them in multi panel sets anyway.

We're right on the vans weight limit, so Im going to give the flexi's a go. Im not buying another controller in any regard, so Ill see how the flexi's go.

The Greca profile polycarb is 16-29mm high, and the Trimdek profile 26mm, so Im hoping that's enough to give them some breathing space. I could double up the polycarb but I'd have to check the weight first so double sheeting doesnt defeat any weight saving

Hi @Crusty181,
I am only guessing, ... but I would suggest that IF you wire panels in series or parallel AND don't install the necessary blocking or bypass diodes, THEN when one panel goes into shade, then that panel becomes a load for the other panel and will heat up. Although this is not a good thing, heavy glass panels may tolerate the extra heat generated much better than flexible panels.

In normal operation (both in similar sunlight), identical panels wired singly, in series, or in parallel should have no bearing on the working of each panel. In parallel or in series (with the correct diodes installed), when one panel is shaded, the other panel CANNOT become a load and will not have to dissipate the extra heat generated.

Just my two-cents worth. I might well be misunderstanding something.

Might as well continue and add my three-cents worth, multiple controllers is another jump in complexity.
Consider that a single solar controller is already trying to be a smart charger AS WELL AS a power supply for the van load. With a smart charger, current into the battery and battery voltage are being monitored to determine the SOC and to select what stage of charging to apply. The potential problem is that the battery is also possibly under a variable load. Try to imagine what a smart charger should do when someone turns on the coffee machine and drags 100A or more and drops the voltage substantially. It would not be hard to imagine it getting confused.

Now, add to that complexity, two solar controllers across the batteries, both trying to determine an appropriate charging state to get the batteries to 100% SOC AND also not overcharge the batteries. Trying to contemplate how to understand what might happen under various scenarios is most likely going to do my head in. I strive for simplicity and as far as I can tell this is just not simple.

Simplicity, IMHO, would be identical panels, wired in series or parallel with correctly sized cable, with correctly installed bypass or blocking diodes into one good quality MPPT controller AND sufficient monitoring to determine solar panel performance, MPPT controller performance, battery SOC, battery condition and capacity, measurement of accumulated power into and out of the batteries, and a thorough knowledge of all loads connected to the batteries. And a generator to kick in when the sun fails to shine or the solar system goes on the blink.

I have a mate who has lived off grid for many years and he has all the above in his solar installation. He monitors, on a daily basis, the state of his system.

Ooops, sorry, that was more like my thirty cents worth. I'm off to have a cider and cool the brain down.

cheers
Mike

 

[Boots in Action]

Hi @Crusty181,
I am only guessing, ... but I would suggest that IF you wire panels in series or parallel AND don't install the necessary blocking or bypass diodes, THEN when one panel goes into shade, then that panel becomes a load for the other panel and will heat up. Although this is not a good thing, heavy glass panels may tolerate the extra heat generated much better than flexible panels.

In normal operation (both in similar sunlight), identical panels wired singly, in series, or in parallel should have no bearing on the working of each panel. In parallel or in series (with the correct diodes installed), when one panel is shaded, the other panel CANNOT become a load and will not have to dissipate the extra heat generated.

Just my two-cents worth. I might well be misunderstanding something.

Might as well continue and add my three-cents worth, multiple controllers is another jump in complexity.
Consider that a single solar controller is already trying to be a smart charger AS WELL AS a power supply for the van load. With a smart charger, current into the battery and battery voltage are being monitored to determine the SOC and to select what stage of charging to apply. The potential problem is that the battery is also possibly under a variable load. Try to imagine what a smart charger should do when someone turns on the coffee machine and drags 100A or more and drops the voltage substantially. It would not be hard to imagine it getting confused.

Now, add to that complexity, two solar controllers across the batteries, both trying to determine an appropriate charging state to get the batteries to 100% SOC AND also not overcharge the batteries. Trying to contemplate how to understand what might happen under various scenarios is most likely going to do my head in. I strive for simplicity and as far as I can tell this is just not simple.

Simplicity, IMHO, would be identical panels, wired in series or parallel with correctly sized cable, with correctly installed bypass or blocking diodes into one good quality MPPT controller AND sufficient monitoring to determine solar panel performance, MPPT controller performance, battery SOC, battery condition and capacity, measurement of accumulated power into and out of the batteries, and a thorough knowledge of all loads connected to the batteries. And a generator to kick in when the sun fails to shine or the solar system goes on the blink.

I have a mate who has lived off grid for many years and he has all the above in his solar installation. He monitors, on a daily basis, the state of his system.

Ooops, sorry, that was more like my thirty cents worth. I off to have a cider and cool the brain down.

cheers
Mike

I would say a good Dollar's worth of advice there @mikerezny !!! I love your techo thinking about the various different scenarios!! Just as a matter of interest, do the thin type panels come with some sort of controller and do they incorporate blocking/and or bypass diodes as part of their system?? In the USA, many a solar panel is just that - a solar panel!! The customer has to add the diodes applicable to their individual operation. I followed a lot of these stories on the internet.
Have you been able to delve into the depths of the link I sent earlier on the effect of heat and current loss (not voltage) on Schottky diodes when used as bypass devices as yet?? Very, very techo!! Even @Bellbirdweb had to pass on that link!! When you start to talk about the wire itself acting as the heat sink in the junction box at the back of the panel, you are really in deep. As you referred in earlier threads, there are lots of Schottky diodes out there and increasing voltage or current needs to be considered if using an MPPT controller. And they are cheap on Ebay and arrive within 3 weeks too.

 

[Moto Mech]

Hi @Moto Mech , are you still going to use the flexi panels or use the 2 X 120W panels?? If going to use the framed panels, go for just the one MPPT controller if you can afford it and there is a need for such outlay. Connected in series will give you heaps!! If still going to use the thin panels and can get some cooling air around the back of the panels, you still might get away with it. The choice is yours. Using one good solar controller IS the way to go, but I understand your issues after bad experiences. Sometimes one has to accept compromises when the ultimate cannot be achieved. Obviously, it would be better to have two controllers of same type and identical because the chances are that there will be little variance in operation. Seems an expensive way to do it, but for the purist worth it. But I am like @mikerezny , I hate spending money unnecessarily on just a whim. I have to have a real need and a high expectation of a worthwhile improvement!!

Ill be running 2 x 200w flexable panels, trust framed panels more but want the weight savings of the flexables.
I think ill try two identical controllers but have a bit of time to decide.

 

[mikerezny]

Hi @Boots in Action,

Have you been able to delve into the depths of the link I sent earlier on the effect of heat and current loss (not voltage) on Schottky diodes when used as bypass devices as yet??

apologies, I haven't had the mental capacity to take that on at the moment.

I am still in another world getting my grey water tote organised so it is compliant, simple, and of course cheap. Looks like I cannot avoid having to fork out 47c at the green shed for a 12mm elbow....damn.
However, I will wait until Thursday night when they have invited me to a tradies night, so I will hopefully get that money back in free food and drink!!!!

It is not uncommon for the leads of components to be used as a heat sink. Or to expect the connecting point to transfer heat away from the component. Otherwise, clamps or specific heatsinks to dissipate the heat generated may need to be used. Sometimes components are put in parallel or series to increase the cooling area to get rid of the heat.

cheers
Mike

 

[Bellbirdweb]

Ill be running 2 x 200w flexable panels, trust framed panels more but want the weight savings of the flexables.
I think ill try two identical controllers but have a bit of time to decide.

@Moto Mech I had assumed you were connecting dissimilar panels. If the panels are the same capacity, connecting them both to a single MPPT controller will work much better than the multiple controllers.

Where you have dissimilar capacity panels having a controller on each works better.

As @mikerezny has said above ensuring there is diode isolation between the panels will reduce shading issues.

 

[Moto Mech]

@Moto Mech I had assumed you were connecting dissimilar panels. If the panels are the same capacity, connecting them both to a single MPPT controller will work much better than the multiple controllers.

Where you have dissimilar capacity panels having a controller on each works better.

As @mikerezny has said above ensuring there is diode isolation between the panels will reduce shading issues.

I was only going on supplier stating not to wire in in parallel or series. Been there and fried $1000 worth of panels

 

[Moto Mech]

But open to and will take on board all opinions still.

 

[Moto Mech]

So in our last van I had a epsolar 4210 mppt controller, 2x 150w flexable panels in parallel, then 2x 250w framed panels once flexables died.
Can get same controller around $170, yes/no? Better one to get?

 

[Bellbirdweb]

I was only going on supplier stating not to wire in in parallel or series. Been there and fried $1000 worth of panels

Provided they are correctly isolated from one another, I can't see how there could be any interaction between the panels.

 

[Boots in Action]

Hi @Boots in Action,

apologies, I haven't had the mental capacity to take that on at the moment.

I am still in another world getting my grey water tote organised so it is compliant, simple, and of course cheap. Looks like I cannot avoid having to fork out 47c at the green shed for a 12mm elbow....damn.
However, I will wait until Thursday night when they have invited me to a tradies night, so I will hopefully get that money back in free food and drink!!!!

It is not uncommon for the leads of components to be used as a heat sink. Or to expect the connecting point to transfer heat away from the component. Otherwise, clamps or specific heatsinks to dissipate the heat generated may need to be used. Sometimes components are put in parallel or series to increase the cooling area to get rid of the heat.

cheers
Mike

Nothing like a bit of food in exchange for some product you cheapskate!! But good luck with you grey water device. Should be pretty easy job not needing much brain power.
Thanks for confirming details regarding wiring to help dissipate heat in electrical components. It is just how it is calculated to prevent "thermal runaway" when conditions are extreme that interests me.

 

[Boots in Action]

So in our last van I had a epsolar 4210 mppt controller, 2x 150w flexable panels in parallel, then 2x 250w framed panels once flexables died.
Can get same controller around $170, yes/no? Better one to get?

Hi @Moto Mech, you have a good MPPT controller already- smart move!! The only improvement necessary is to wire them in SERIES and to make use of higher voltage that has been successfully done by some of us already. Remember, current coming through to your controller will be only approx 7A, but VOLTAGE will be approx 40 V. When the MPPT controller works on that, you will have a lot more amps available than if connected in parallel especially if batteries are low. Shading/partial shading will be less of a problem and you can use thinner wire. Also better in cloudy conditions.
Your controller can handle up to 100 V, BUT you need to have the BYPASS diodes properly connected to protect your panels. Blocking diodes are not necessary as controller takes care of that and prevents current flow back through panels at night or when panels are not producing.

 

[Crusty181]

So in our last van I had a epsolar 4210 mppt controller, 2x 150w flexable panels in parallel, then 2x 250w framed panels once flexables died.
Can get same controller around $170, yes/no? Better one to get?

Cant give you a review yet, but I recently purchased the Epsolar 4210 for $162 on eBay

 

[Moto Mech]

Hi @Moto Mech, you have a good MPPT controller already- smart move!! The only improvement necessary is to wire them in SERIES and to make use of higher voltage that has been successfully done by some of us already. Remember, current coming through to your controller will be only approx 7A, but VOLTAGE will be approx 40 V. When the MPPT controller works on that, you will have a lot more amps available than if connected in parallel especially if batteries are low. Shading/partial shading will be less of a problem and you can use thinner wire. Also better in cloudy conditions.
Your controller can handle up to 100 V, BUT you need to have the BYPASS diodes properly connected to protect your panels. Blocking diodes are not necessary as controller takes care of that and prevents current flow back through panels at night or when panels are not producing.

Ok, cool. Being a total 'stranger' to diodes, for my setup(2x 200w flexable panels, epsolar 4210 and 2x 100ah batteries) with panels wired in series, what type/size bypass diodes do I need?

 

[Boots in Action]

Ok, cool. Being a total 'stranger' to diodes, for my setup(2x 200w flexable panels, epsolar 4210 and 2x 100ah batteries) with panels wired in series, what type/size bypass diodes do I need?

Hi @Moto Mech , I would go for 20sq45 or 20sq60. Code is: first number is amp rating, sq is Schottky type diode and last number is voltage rating. Cheap as chips on Ebay. I just ordered the latter and it cost me $2-45 AU for five, delivered. Other types I have received were only $3-60 for 10. If you have any trouble, I can send you the link. Was just going to use the 45V type with two panels in SERIES, but kept my options open by going for the 60V type in case I connected 3 panels in SERIES. I will be doing a thread on connecting these up in the next couple of weeks, if you have any problems. Nearly forgot!! There is a reference to diode connection in an earlier thread to @Crusty181 on Alt e web site which explains fitting of diodes in easy understanding form.

 

[mikerezny]

Ok, cool. Being a total 'stranger' to diodes, for my setup(2x 200w flexable panels, epsolar 4210 and 2x 100ah batteries) with panels wired in series, what type/size bypass diodes do I need?

Hi @Moto Mech,
good advice from @Boots in Action.

One extra detail is to determine how each of your panels is internally configured.

Some panels are simple and have only two thin wires coming from the cell array to the connection box glued on the back. They may also already have a bypass diode fitted.

Other panels have three wires. This means that the panel is divided into two sub panels which are then wired in series. In that case, you may already have two bypass diodes (one across each of the sub panels). This is good because then you have nothing further to do, just wire each of the panels in series.

Regardless of what diodes, if any, are currently fitted, you can still replace them with Schottky diodes such as @Boots in Action has posted.

It would be good if you could post a picture of the interior of the connection box clearly showing the contact strips coming from the solar cell arrays. Then we will be able to give you better assistance.

cheers
'Mike

 

[Dobbie]

An observation......for simplicity and to reiterate what most of the early discussion focused on

• Most solar panels now come with blocking diodes
• A portable panel, to supplement the standard roof panels, must have its own separate controller and be wired directly to the battery
• Attach regulators as close to the battery as possible
• Keep the wiring to the best possible size..6 or 8
• Keep the portable panel cable as short as possible, within the range needed...10m is possible if the cable size is correct
• Regulator must be able to cope with panel specs...at least 20 amps, preferably 30
• Regulator can be MPPT for optimum results but a PWM is adequate for most occasions. MPPT is superior, but most of the others are OK for basic requirements
• Keep panels clean
• Know your power requirements and charging and battery capacity before overspending
• KISS

You guys are certainly doing a good job with the investigation but, as said earlier, I think we're getting bogged down a bit in the complexities of MPPT, diodes etc...which is fine but doesn't really help sorting out the more basic requirement of most who are looking to set up a good 12v chárging system. I'm concerned that confusion will result.

I know many of us have been using good 12v systems for many years by following basic principles ...in our case for over 20 years....and I know if I'd stumbled on this very complicated discussion, needing some simple advice on solar charging, I'd run a mile!

 

[Moto Mech]

Right on que, panel turned up today. Pic of inside junction box

 

[mikerezny]

View attachment 56927 Right on que, panel turned up today. Pic of inside junction box

Hi @Moto Mech,
oh good. This looks like a simple panel with a single array since I can see only two wires coming in from the top from the solar cell.
The square black device ACROSS the cell output looks to be two diodes wired in parallel as a BYPASS diode.

The photo is not quite clear enough. Is it possible to read the part number on the device? It looks like 20SQ???

cheers
Mike