RV Solar Calculator

[Raspy]

Gordon,

Got it. Thanks.

[k corbin]

sounds like you are going to have plenty of power for the fridge and heater. also enough to run some electrical appliances. Probably not enough to run AC. But certainly an instapot meal, a coffee maker, a small microwave. Of course not all at the same time.



Take advantage of having a lot of solar input in the morning and early afternoon for using something such as an instapot. That way you will have some time to recover what it takes out of the battery before night fall.



Do not save all of your high power use for late in the afternoon or the evening as you won't have the advantage of offsetting using the sun during the part of the day you get the most input. Make "hay" while the sun shines!

[Jon Vermilye]

Originally Posted by Raspy

Gordon,
Not sure what you are saying here. The inverters are only about 90% efficient, so there is a 10% loss when using them. Plus, they have standby losses that can add up if left on while not running any appliances. Battery charging also has losses of up to about 20-30%, as I understand it. Those two losses must be accounted for somehow and show up as reduced system capacity. So that extra power must also be accounted for somehow too. With batteries and inverters, you put more in than you get out. Plus, with batteries, the higher the amp draw, the less is available overall. So running a microwave, for example can seem to use more than calculated, because the inverter wastes power, the battery wastes power when recharging, and the batteries have lower overall capacity with a heavy amp draw. These three things together might total to a 50% loss in some cases.

Also, everyone should be cautious in estimating solar performance. A 300 watt system will not produce 300 watts if laid flat on the roof. Tracking systems produce about 250% overall, of what flat systems produce.

We all want to have more power and it seems demand will always rise to meet supply. So even a well designed system will seem weak eventually, as more appliances are added. We all have to live within our solar system's abilities. Just yesterday, I got a new electric bike for instance, and charged it from my inverter. A load I did not account for a few days ago. And a large load too.

One point - While this is a good consideration when using lead acid batteries, he is going to lithium, a whole different ballgame.

According to Battleborn, the charging efficiency for their batteries is 99%, and the Peukert multiplier (used to determine the effect of large loads on the battery) is 1.05, much better than lead acid. Both of these, along with shorter charging times & still having 12.3V or so at 10% charge are a few of the nice things about lithium. Of course, there is the bad - cost, but that is slowly coming down.

[Raspy]

Jon,

Thanks for the info on lithium efficiency and the Peukert multiplier. Much better than I realized.

[ThomasC]

Originally Posted by Rzrbrn

I Just talked to the RV SERvice center that I expect to be doing my solar install. Keep in mind that I do not know anything about electricity. I have a 2019 Big Foot 25RQ solar ready (don't know exactly what this means). Please excuse the upper case, I am lazy and am just copy and pasting. I just had a phone conversation to get the overall proposal, and will meet with the RV Service tech to get a written estimate within the next couple of days.

OK, this is what is being proposed:

Renogy 600 WATT 24 VOLT SOLAR PREMIUM KIT (4 panels in front + 2 panels in the rear, all on top permanently mounted on tracks bolted to the roof).

This kit includes:

6 ECLIPSE - 100 WATT 12 VOLT MONOCRYSTALLINE SOLAR PANELS

ROVER LI 40 AMP MPPT SOLAR CHARGE CONTROLLER with Blue tooth module, paired to the Renogy BT APP. The Renogy BT APP allows remote monitoring. This kit also consists of six sets of mounting Z-Brackets, branch connectors, one 20ft 10AWG MC4 Adaptor Kit, one 8ft 8AWG Tray Cable, and fusing components for protection of the controller and battery.

Not in kit but being added:

MAGNUM INVERTER. Not certain which one at this point, will know and update after I visit the RV Service technician.

USB ports will be wired with on/off switches

Two 100Ah 12V LiFePO4 Deep Cycle Batteries, expandable to two more if desired at a later date.

What do you think?

Not certain what else is to be include, will update later.

I am very interested in solar and I don't know enough about it. So I have been paying attention a lot of different sources and following many threads on various forums.

I was an auto/tractor mechanic all of my life and have considered myself quite good with 12volt DC systems. My latest hobby of electric bikes has me quite familiar with current battery technology. I have not found a good source of information on solar until today. Oh it is late, make that yesterday.

In another thread here "Battery upgrade on my Bigfoot" a blog was mentioned and I have been reading it for more than 6 hours. https://handybobsolar.wordpress.com/

Enough of what he says checks with everything that I have learned as a mechanic and it makes me feel it is a good source of information. You might want to spend some time reading his blog.

One thing I didn't know is that even a small shadow from a vent, AC, or TV antenna can almost shut down a solar panel. So placement is critical. I have read only half of his blog and I will likely go over it again and take notes. I will do solar later in the year after I map out the roof of my Bigfoot.

[gordon2]

Originally Posted by ThomasC

. I have not found a good source of information on solar until today. Oh it is late, make that yesterday.
...

Really? Almost all of the companies in the trade have helpful web pages...

Support for Bogart Engineering Products - Bogart Engineering

https://www.renogy.com/ (See "Learn" tab)

https://gpelectric.com/ (See "Learning Center" tab)

https://www.altestore.com/learn/

https://www.solar-electric.com/learning-center

https://www.backwoodssolar.com/learning-center

And a long list of blogs, forum posts, etc on the subject:

TOPONAUTIC Outdoor News-Events-Recipes: Solar: My first venture into building a solar system
http://www.fiberglassrv.com/forums/f...tem-45885.html
https://forums.trailerlife.com/Index...g/1/page/1.cfm
RV Electrical

etc...

This forum alone has lots of posts, some more helpful than others:

https://www.google.com/search?q=sola...berglassrv.com


and some items in the document center:
Fiberglass RV - Document Center - Electrical

Some of the trailer-specific web sites have docs or articles in addition to forum threads, for example:

https://www.scampowners.com/solar-scamp-trailers


And finally, this post that is the reason I will not use VHB tape alone to mount metal framed solar panels on the roof...

Our solar panel blew off!! - Escape Trailer Owners Community

That should keep you busy

[ThomasC]

Thanks for that list of links. I have been to most of them but I was looking for someone who was running off grid. Someone who had been there, done that. Handybob's solar blog rang enough bells with this retired lifetime mechanic that I believe he is a good source of information.

Who do you believe? What you mentioned about the tape to hold down panels is an example. The first time I saw that I just shook my head and then later I read about panels blowing off. So my gut feeling was right. All of those companies with help and learning centers are trying to sell systems so do you believe them?

I have been through four years of building and experimenting with electric bikes. The amount of bad information out there is incredible. So who do you believe? I am going to listen to Handy Bob because I don't want to spend 4 years and thousands of dollars learning solar systems like I did with the ebikes.

[Jim Bennett]

Originally Posted by ThomasC

I am very interested in solar and I don't know enough about it. So I have been paying attention a lot of different sources and following many threads on various forums.

This is a great way to do it. I know AC electricity quite well having built electrical substations for 14 years when younger, but needed to learn the intricacies of solar. It is quite simple but still needed to put the pieces together.

One thing I would caution, and you likely know, is that a lot of the forum discussion, though it has helped me out a lot, is full of varying personal opinion. Though these are very useful to go through, not everything is right for everyone.

Man, you should have seen the negative comments I got when first considering a new for of semi-flexible panel, as many truly are not all that great physically, but doing my research found that the newer ETFE coated ones by Lensun to be quite good, so I went for it. 3 years later they are looking and working like new, and many other folks have now gone to using them. You can't even tell they are on my trailer unless you stand way to the rear because the roof slopes to the back. BTW, I did use Eternabond tape top hold the 4 panels down, and it has worked great. A good VHB tape would work well.

Now, don't take what I said as gospel

[Rzrbrn]

After talking with the person that will be doing the installation, we have decided the 12V system to be the best. It will not be the original suggestion of 24V. I expect he will have the quote maybe by next Monday and I will post it here as an update to my original post.

[OCJohn]

Keeping Jim’s point about opinions in mind, the ratio of panel wattage (600) to battery storage (200Ah) appears more biased toward panel output than than storage compared to many systems I've read about. That may be intentional to compensate for non-tilting panels and/or a lot of camping in winter or northern latitudes. No problem there. But I'd question if the 200Ah battery capacity is a pricing strategy aimed at using lithium within a fixed budget. Put another way, are they giving you less battery storage than might be desirable just so they can sell you lithium rather than less profitable AGM or flooded lead acid batteries?

I don't have an answer to that. I've just gone thru a lot of the same decision making you are and concluded I just couldn't get the storage capacity I wanted for a price I could justify with lithium. Again, no judgment, and our budgets may be totally different. I'm just raising the questions I went thru. Like you, I'm still at the beginning of the solar journey so take it with a dose of salt. JonV's switch from 6v wet cell to lithium speaks volumes as someone who's done both. Then again, Jim has/had portable panels he never needed...

JonV – I may have missed it, but did you mention the storage capacity of your new liths? You had 232Ah with the 6v = 116Ah of normal usable storage, yes? Where are you now with the lithiums?

[Jim Bennett]

For reference, the majority of solar panels are around 18V, not 12. The solar controller adjusts, basically PWM discarding what is above the charge coils drawn at the time and MPPT converting it all to the desired voltage.

I wired mine in at 3 cutting the charge current in half, but really the potential line loss is so minimal due to the short runs. If I was doing it again, I would just keep it at 18 volts myself.

[Jon Vermilye]

[QUOTE=OCJohn;766346]Keeping Jim’s point about opinions in mind, the ratio of panel wattage (600) to battery storage (200Ah) appears more biased toward panel output than than storage compared to many systems I've read about. That may be intentional to compensate for non-tilting panels and/or a lot of camping in winter or northern latitudes. No problem there. But I'd question if the 200Ah battery capacity is a pricing strategy aimed at using lithium within a fixed budget. Put another way, are they giving you less battery storage than might be desirable just so they can sell you lithium rather than less profitable AGM or flooded lead acid batteries?

I don't have an answer to that. I've just gone thru a lot of the same decision making you are and concluded I just couldn't get the storage capacity I wanted for a price I could justify with lithium. Again, no judgment, and our budgets may be totally different. I'm just raising the questions I went thru. Like you, I'm still at the beginning of the solar journey so take it with a dose of salt. JonV's switch from 6v wet cell to lithium speaks volumes as someone who's done both. Then again, Jim has/had portable panels he never needed...

JonV – I may have missed it, but did you mention the storage capacity of your new liths? You had 232Ah with the 6v = 116Ah of normal usable storage, yes? Where are you now with the lithiums?[/QUOTE]

I have 2 100 amp hour lithium, however they are the equivalent of 400 amp hours of lead acid/AGMs in that you can take them down to 10% repeatedly without damage. At 10% they are still producing over 12V.

I'm charging them with 320 watts of rooftop solar that is currently tilted to the south at the correct angle for Phoenix, AZ (I'm in Quartzsite) in early January, plus a portable 160 watt panel that I leave aimed at the morning sun.

I didn't tilt the rooftop panels or add the portable until after 3 days of heavy clouds. Even then I was only down to 70%, but I like to keep full batteries.

As to how I like them - they are great. They charge much faster than the lead acid batteries, and even when down 70% will still let me use the microwave on the inverter. With the exception of the AC, I can now treat the trailer as if it was hooked to a 120V pedestal.

[ThomasC]

Originally Posted by Jim Bennett

Man, you should have seen the negative comments I got when first considering a new for of semi-flexible panel, as many truly are not all that great physically, but doing my research found that the newer ETFE coated ones by Lensun to be quite good, so I went for it. 3 years later they are looking and working like new, and many other folks have now gone to using them. You can't even tell they are on my trailer unless you stand way to the rear because the roof slopes to the back. BTW, I did use Eternabond tape top hold the 4 panels down, and it has worked great. A good VHB tape would work well.

Now, don't take what I said as gospel

I was thinking of flexible panels until I started hearing all of the horror stories associated with them. Well more reading and research is needed. Thanks for the tip.

Did you do a write up on your install. I read somewhere that if you are South in the summer, your flexible panels will be toast in a year. Are you a cool weather camper?

[Jim Bennett]

Originally Posted by ThomasC

I was thinking of flexible panels until I started hearing all of the horror stories associated with them. Well more reading and research is needed. Thanks for the tip.



Did you do a write up on your install. I read somewhere that if you are South in the summer, your flexible panels will be toast in a year. Are you a cool weather camper?

Where did you hear horror stories associated with the ETFE panels, like the ones Lensun sells? In my vast research I found none. Some on older styles though.

I did do a writeup on the Escape forum. I can find and post a link in the morning. Never heard of problems with hear either, and know now if a few in the south with them. Mine liked Arizona and Mexico fine.

[Daniel W]

This is a super awesome and timely post.


I'm in early of designing a solar system for our 25RQ.


I usually lean toward the overkill side of project designs.


I'm currently leaning toward a system...
-1020w panels (6 x 170w Zamp panels)
-500ah Battleborn Lith Batts
-either 2k or 3k Victron multiplus inverter charger
-appropriately sized Victron solar charge controller
-Victron monitors


Will be installing panels with 3M VHB tape.


Seems to be one camp of wiring panels in series...
...and another camp of wiring panels in parallel.


I'm probably going to wire combo series-parallel...
3 strings of 2 in series panels.


Interested in this audience's thoughts of series vs parallel panel wiring.


I am hoping that a series-parallel approach gives me both the benefit of minimizing shading impact (parallel advantage) and plenty of voltage to the charge controller (series advantage).
Thoughts and criticisms welcome.

[ZachO]

There are a ton of internet "horror" stories about the older technology flexible panels. That's obviously what he's talking about. The newest generation of flexible panels seem to have mostly worked out those issues of overheating, cracking and scratching.

You're going about this in a good way, it seems to me. There's a ton of information out there posted by people who are either trying to sell you something, or don't really know what they're talking about. Everyone is an expert these days on the internet, and many are building websites and posting tutorials to get ad revenue, when they don't know any more than anyone else who did a basic amount of internet research. So I'm with you on that one.

Henry sounds like you've got things going. Whatever system you end up with will be a great start. You may or may not find that as you use it and learn more yourself, you may find that a slightly different setup would have been better. Only experience will tell you. IF you can afford it, it's often better to just jump in, buy a system and learn as you go, rather than becoming an expert before you're even using solar. Anyway we'll be interested to hear how it goes for you.

[Rzrbrn]

Daniel, my RV service tech who will be installing the solar is to get me a proposal this coming Monday. If I get it then I will post here. It may give you some ideas.

Thanks Zach. I will try to remember to post how it works after the next camping season. We have been going out 1x per season. That 1x has been 2 to 4 months of camping, usually getting home just before Thanksgiving.

[Jim Bennett]

Originally Posted by ThomasC

Did you do a write up on your install.

Here it is. I have found the 240W of panel does most of our needs and keeps the batteries topped up daily, often by noon. Only on a couple of heavy overcast and rainy days when battery was used a fair bit did I not get a full charge. If I was to worry at all, I would just connect my portable for good efficient charging.

As I have mentioned, I just love the out of site, clean feature of this method.

Solar Installation - Escape Trailer Owners Community

[ThomasC]

Originally Posted by Jim Bennett

Where did you hear horror stories associated with the ETFE panels, like the ones Lensun sells? In my vast research I found none. Some on older styles though.

I did do a writeup on the Escape forum. I can find and post a link in the morning. Never heard of problems with hear either, and know now if a few in the south with them. Mine liked Arizona and Mexico fine.

It must have been older panels. When I start researching a subject I will do a web search go to videos and blip through watching things that catch my eye. Burning solar panels are definitely eye catching.

I will appreciate that link. It is kind of hard/time consuming to search for those things sometimes. I would much rather do flexible panels even if they are less efficient and more expensive.

[ThomasC]

All of this solar talk has made me remember a blog that I would go to for Bike battery info. The author is a computer IT guy that is off grid "imagine that" and he built a solar shed to work from. He has a crazy blog and writes about everything. He also tests everything.

If you some extra reading here it is.

https://syonyk.blogspot.com/search/label/Solar%20Shed

Oh yeah he has AC in the shed. He also has a backup suitcase generator.