Solar panel question

[AJMike]

This question never occurred to me until I began to look for a 4th 100 watt solar panel to add tho what is already on the roof of my Winnie Fuse. One of the things I was concerned about was finding the most efficient solar panels, although the offerings on Amazon rarely contain efficiency ratings.

However I assume all 100 watt solar panels are supposed to deliver 100 watts, although perhaps at different voltages and currents, so it seems self-evident that the smallest 100 watt solar panels (in terms of area, square inches or square centimeters), would automatically be the most efficient, but is that true?

The Renogy panel I bought was listed as the compact design, is 827 square inches, cost $96 (plus tax) and is listed as "Reliable". Another Renogy panel, the Eclipse, is 859 square inches and cost $171 and is listed as "More Efficient". Clearly there is a disconnect here. If the physically larger panel produces no more power than the smaller one how can it be considered to be more efficient?

Or am I missing something here?

[Winterbagoal]

Just a suggestion here, because it might resolve almost every problem you've come up with to date, and not intended as condescending, but how about taking a short drive up I-17 to get some off grid industry knowledge based, real world practical, answers to all of your questions?

These guys are among the nation's best at off grid stuff, and have been around (almost) forever.
They do it all....

https://www.solar-electric.com/contact/

They're not far from you in AZ.

Northern Arizona Wind & Sun
3695 E Industrial Drive
Flagstaff, AZ 86004

[creativepart]

Here’s a link to an article that discusses solar panel efficiency:

https://news.energysage.com/what-are...on-the-market/

Renergy’s panels are shown as having a min efficiency of 15.3% and a maximum of 18.5%.

[AJMike]

Originally Posted by Winterbagoal

how about taking a short drive up I-17 to get some off grid industry knowledge based, real world practical, answers to all of your questions?
.
.
.

Northern Arizona Wind & Sun
3695 E Industrial Drive
Flagstaff, AZ 86004

Actually my experience with them was not positive.

I purchased my Victron DC-DC charger from them and called to ask some questions about it, and came away with the feeling that they were guessing at the answers.

1) When I started to install the charger I read the manual that came with it and saw that the distance I needed to run the wire meant that I should be using 5 gauge wire. OK, but I could not find 5 gauge wire at either HomeDepot or Lowes so I called them to find out if they could sell me 5 gauge wire. They told me that the charger, which uses push connections, would not take larger than 6 gauge wire.

I told them that the manual said to use 5 gauge for the distance I needed to run, and suddenly all I got was silence. Then I was told again nothing bigger than 6 gauge would fit. Again I told them what the manual said, and was then told that 6 gauge was probably large enough. If necessary I could mix the 5 gauge and the 6 gauge wire.

Clearly Victron expects people to use what they suggest, 5 gauge wire, and 6 gauge does not completely fill the wire hole so 5 gauge is probably right, but they would not acknowledge that the manual even said that.

2) I asked them why the manual stated that I should be using a 60 amp fuse with a charger that had a specified output of 30 amps, and never got a decent response, and after that they became very short with me and clearly did not want to answer any more questions.

[DavidM]

The terms reliable and efficient are pure marketing fluff. But to be practical look for the highest output panel in watts that will fit your available space as long as it is a nominal 12V panel.

And lets talk about another issue that your post implies: mixing panels. Yes different panels have different voltage and current ratings. The main ones involved at least in a MPPT controller are Imp and Vmp, the current and voltage where a panel produces its maximum rated current.

If you have two panels, with different Vmp and Imp values (and they only vary by maybe a volt) then the controller has to find a happy medium, probably in between the two that it will operate at. Yes you will lose a bit of wattage due to this slight variation but I bet it will be less than 5% and certainly better than a PWM controller.

But I believe you are going to stay with your PWM controller. A PWM controller will adjusts its pulsing to keep the input voltage well below the Vmp values, somewhere in the 13-14.5V range which is what the battery needs. That is much less than the Vmp values of either panel which are typically 17-18 V and you will lose even more power output. The difference in the two Vmp values will probably be insignificant in this situation.

David

[AJMike]

Originally Posted by creativepart

Here’s a link to an article that discusses solar panel efficiency:

https://news.energysage.com/what-are...on-the-market/

Renergy’s panels are shown as having a min efficiency of 15.3% and a maximum of 18.5%.

Thanks for the link. I glanced through it and found it interesting, but it also left me with some questions.

Renogy lists some of their solar panels as being built with SunPower cells, so I would think that those panels would have the SunPower efficiency rating, but it is not shown on their table.

The article seems to be centered on solar panels for the home. I wonder if there is any variation with panels that are designed for RVs. I have never looked at solar penels for the home because they did not seem cost effective, at least for how long we would be living here, but I would assume that home panels are built differently than panels for RVs, which would be smaller and lighter.

Two of the solar panel manufacturers whose efficiency I have seen praised in some online articles (which, for all I know, may actually be advertisements) , Newpowa and HQST are not listed. And, of course, they may well be identical to some other panels, only branded differently. It is impossible to be sure.

At some basic level it seems reasonable to assume that smaller panels that produce the same power should be more efficient, but what I read does not seem to back that up, and I don't know why.

[BobC]

If someone does encounter a situation where a controller, charger or other device will only accept a smaller gauge wire than the length of the total run requires, splicing in a short segment of smaller gauge shouldn't be a problem. The gauge required for a given voltage/amperage/length is a function of length and each segment stands on its own. You should still use the Voltage/Amp/Distance/AWG table to confirm that the gauge of your shorter segment is OK but, in doing so, you evaluate it based on its length, not that of the total run.

Also, some user manuals specify wire gauge based on wide ranges of "run", like "over 20 feet", use X AWG. Clearly, 21' will be OK with a smaller gauge than 30', so use your tables.

[AJMike]

Originally Posted by DavidM

The terms reliable and efficient are pure marketing fluff. But to be practical look for the highest output panel in watts that will fit your available space as long as it is a nominal 12V panel.

That is basically what I thought I was doing when looking at the sizes of the various 100 watt panels. My assumption, perhaps incorrect, was that the smaller the 100 watt panel the more efficient it would be.

Perhaps all that efficiency stuff is marketing fluff, but it does not make much sense to me if it takes a larger panel to produce the same power, and then to claim that the larger panel is more efficient.

Originally Posted by DavidM

And lets talk about another issue that your post implies: mixing panels. Yes different panels have different voltage and current ratings. The main ones involved at least in a MPPT controller are Imp and Vmp, the current and voltage where a panel produces its maximum rated current.

If you have two panels, with different Vmp and Imp values (and they only vary by maybe a volt) then the controller has to find a happy medium, probably in between the two that it will operate at. Yes you will lose a bit of wattage due to this slight variation but I bet it will be less than 5% and certainly better than a PWM controller.

But I believe you are going to stay with your PWM controller. A PWM controller will adjusts its pulsing to keep the input voltage well below the Vmp values, somewhere in the 13-14.5V range which is what the battery needs. That is much less than the Vmp values of either panel which are typically 17-18 V and you will lose even more power output. The difference in the two Vmp values will probably be insignificant in this situation.

When adding the last panel I did look at the voltages involved, and the new panel has the exact same VOC as the existing panels. I am not sure how important that is, but it was something I was thinking about.

When the flexible panels finally die I expect to replace them with matched rigid panels and at that time may well choose to upgrade the solar controller to some MPPT model. The problem is that the existing controller fits into the information section of the RV along with all of the other meters and if I replace it with an MPPT I am not sure what to do with the hole that will be left in the wall. Perhaps there is an MPPT model that will fit, but I doubt that based on what I have seen available on Amazon.

But the existing flex panels are probably good for another year or two so all of that is a bit in the future.

[AJMike]

Originally Posted by BobC

If someone does encounter a situation where a controller, charger or other device will only accept a smaller gauge wire than the length of the total run requires, splicing in a short segment of smaller gauge shouldn't be a problem. The gauge required for a given voltage/amperage/length is a function of length and each segment stands on its own. You should still use the Voltage/Amp/Distance/AWG table to confirm that the gauge of your shorter segment is OK but, in doing so, you evaluate it based on its length, not that of the total run.

Also, some user manuals specify wire gauge based on wide ranges of "run", like "over 20 feet", use X AWG. Clearly, 21' will be OK with a smaller gauge than 30', so use your tables.

Sure. And that is what I had to end up doing. I added 6 gauge wire to the end of the 4 gauge that ran to the compartment and used it to hook up to the charger.

But the point is that the folks at the shop apparently were not familiar enough with the product to even know what was supposed to be used. That just did not fill me with confidence about their expertise.

[Winterbagoal]

Originally Posted by AJMike

Actually my experience with them was not positive.

I purchased my Victron DC-DC charger from them and called to ask some questions about it, and came away with the feeling that they were guessing at the answers.

1) When I started to install the charger I read the manual that came with it and saw that the distance I needed to run the wire meant that I should be using 5 gauge wire. OK, but I could not find 5 gauge wire at either HomeDepot or Lowes so I called them to find out if they could sell me 5 gauge wire. They told me that the charger, which uses push connections, would not take larger than 6 gauge wire.

I told them that the manual said to use 5 gauge for the distance I needed to run, and suddenly all I got was silence. Then I was told again nothing bigger than 6 gauge would fit. Again I told them what the manual said, and was then told that 6 gauge was probably large enough. If necessary I could mix the 5 gauge and the 6 gauge wire.

Clearly Victron expects people to use what they suggest, 5 gauge wire, and 6 gauge does not completely fill the wire hole so 5 gauge is probably right, but they would not acknowledge that the manual even said that.

2) I asked them why the manual stated that I should be using a 60 amp fuse with a charger that had a specified output of 30 amps, and never got a decent response, and after that they became very short with me and clearly did not want to answer any more questions.

I didn't know you'd already dealt with them. Sorry for wasting your time.

As an after thought (OK, it's an unsolicited opinion), I guess if you take the manufacturer's word at everything, and follow their instructions to the letter, you'll never have any warranty issues, and may even have grounds for litigation downstream in the event of a catastrophic failure.
I'm inclined to think that NAZWS have applied some extensive real world experience, and perhaps some practical electrical/mechanical installation engineering to the Victron stuff, and found that the factory specs are overkill. If they sold it, and said you can do x, y, z, with it, I'd trust their judgement, but I'd certainly get it in writing.
Sorry, just more idle speculation from another off grid newb.

[DavidM]

I would put Victron near the top in supplying high quality DC stuff along with Magnum and Mastervolt. But like anyone else, the people who answer telephone questions are just people. They sometimes don't know the answer to your question and sometimes fake it.

But I would prefer them to Chingtek or similar any day.

David

[AJMike]

Originally Posted by DavidM

But I would prefer them to Chingtek or similar any day.

As would I.

I am not questioning Victron. In fact I own both their battery monitor and their DC-DC charger. All I was trying to point out is that sometimes the people who work at some of the vendors selling their product are not as knowledgeable as they might be.

If I could have I would have checked with Victron directly but I don't know any way to call them for tech support here in the US and I don't have a support email address for them.

[Old Navy]

Originally Posted by AJMike

If I could have I would have checked with Victron directly but I don't know any way to call them for tech support here in the US and I don't have a support email address for them.

Both in support and products, they are Eurocentric. Some of their products don't even have a US version, like the new Multiplus II series and the Phoenix Smart IP43 series Charger. They do have a pretty good Community site for "crowd support" with both Victron employees and community members helping people.

VICTRON COMMUNITY

[AJMike]

Originally Posted by Old Navy

Both in support and products, they are Eurocentric. Some of their products don't even have a US version, like the new Multiplus II series and the Phoenix Smart IP43 series Charger. They do have a pretty good Community site for "crowd support" with both Victron employees and community members helping people.

VICTRON COMMUNITY

Thanks for the link. I did not know that there was a Victron forum, so at least now I have some place to ask questions.

[Kim Petersen]

I am confused as well, I have been a professional electrician for over 50 years, (retired now) and have never in my life found a 5 gauge wire. it is not listed in the NEC, it might be a wire size, but it is not an electrical wire size. perhaps the literature was a misprint? A 6 AWG wire could be adequate for the current you would expect to receive from the solar panel.

[AJMike]

Originally Posted by Kim Petersen

I am confused as well, I have been a professional electrician for over 50 years, (retired now) and have never in my life found a 5 gauge wire. it is not listed in the NEC, it might be a wire size, but it is not an electrical wire size. perhaps the literature was a misprint? A 6 AWG wire could be adequate for the current you would expect to receive from the solar panel.

5 gauge wire does exist and you can buy it in small pieces on Amazon. One example is here. And it is not an error in the manual because that gives wire sizes in mm2 cross-section that correspond to 7, 6 and 5 gauge, depending upon the length of the run. Since it is a Victron product that size is probably more common in Europe than in the US, but it does exist as well here as evidenced by the Amazon web page.

However the wire is not to carry current from the solar panels. It is the input and output of a DC-DC charger carrying current from the alternator to the charger and from the charger to the Lithium batteries and in this case we are talking about 30 amps on the output side and somewhat more on the input side.

[Kim Petersen]

Thanks AJMike, I am not familiar with the way the Europeans wire things, sorry to butt in, I'm just USA all the way.

[rarebear.nm]

IN the US common wire gauge sizes are in the even numbers above 1 gauge, 2, 4 ,6..... Starting at 1 gauge the odd numbers are sold, 1, 1/0, 2/0, 3/0, etc.
The odd numbered wire sizes can be found but are not typically sold by the big box stores.


When I need to use a wire gauge as per a chart that will not fit into a hole, I'll very neatly trim off enough strands to allow it to fit. In some cases I may use a splice block to splice in a different wire size. Generally I don't like any more splices/connections then is required, more so in an RV. I concerned about frayed wire ends when trimming strands, you crimp a ferrule on the end that covers the stray ends. Provided you have the required crimping tools for that wire size and the necessary ferrules. IMO it never huts to use ferrules on stranded wire when connecting to a lug of some kind. I also like to use adhesive double shrink tubing on the ends to seal things.

[AJMike]

Originally Posted by Kim Petersen

Thanks AJMike, I am not familiar with the way the Europeans wire things, sorry to butt in, I'm just USA all the way.

No reason to be sorry.

I am always glad to get a variety of opinions, and I almost always learn something when people post. Your post was no exception so I am glad you responded.

[DavidM]

Originally Posted by rarebear.nm

IN the US common wire gauge sizes are in the even numbers above 1 gauge, 2, 4 ,6..... Starting at 1 gauge the odd numbers are sold, 1, 1/0, 2/0, 3/0, etc.
The odd numbered wire sizes can be found but are not typically sold by the big box stores.

When I need to use a wire gauge as per a chart that will not fit into a hole, I'll very neatly trim off enough strands to allow it to fit. In some cases I may use a splice block to splice in a different wire size. Generally I don't like any more splices/connections then is required, more so in an RV. I concerned about frayed wire ends when trimming strands, you crimp a ferrule on the end that covers the stray ends. Provided you have the required crimping tools for that wire size and the necessary ferrules. IMO it never huts to use ferrules on stranded wire when connecting to a lug of some kind. I also like to use adhesive double shrink tubing on the ends to seal things.

Use #4 gauge, trim the extra strands, heat shrink the end if concerned about fraying and screw it down.

It could have been done this way, much quicker than reading all of the posts wondering what to do about it .

David