Wanting to increase solar

[AirMiles]

Originally Posted by Paprika

If I understand correctly, you can't do it the way you mentioned, because the voltages wouldn't match up. Here's how it's done:

In a typical series/parallel solar panel setup, you have at least four panels, and you connect pairs of panels in series; then you wire each pair in parallel with the other pair.

For example, a commonly used 100 watt panel produces a maximum of about 5.5 amps at about 18 volts. Wire two of these in series, and you double the voltage to 36 V, but still at 5.5 A. Wire two of these series pairs in parallel with each other, and you double the amperage, so you now have 36 V at 11 amps.

The drawbacks: you have to have pairs of panels, and your solar controller needs to be an MPPT type to take advantage of the higher voltage. The advantage: voltage drop in the wiring between the panels and the controller is cut in half. That means much better efficiency if you're using existing wiring, or smaller wiring (less expensive and easier to work with) if you're installing a new system.

With respect to shading, a series/parallel setup is a compromise. An all-parallel setup is least affected by partial shading, since each panel is unaffected by the others, but it requires large-gauge wiring if it is to avoid serious voltage drop (= wasted power). An all-series setup would let you use much smaller-gauge wiring with no voltage-drop penalty, but shade falling on one panel would affect all the others. A series/parallel setup is somewhat vulnerable to partial shading, but it lets you minimize voltage drop. It's a compromise that has worked well for many of us.

Exactly right.

One other benefit of a series-parallel configuration is that the double voltage allows your solar controller to begin charging with less light and continue charging with less light thereby extending it’s charging hours. My solar charger is putting amps into the battery from the crack of dawn until it’s dark. Of course there are very few amps produced at the extremes. I also think the double voltage is more effective with overcast skies. With double voltage, you always have more than 14.4V available to charge the battery under any light conditions. ( does a parallel configuration with an MPPT controller increase the voltage under low light conditions?)

[Fair_Enough]

Originally Posted by Bobbo

When we bought our FC 23FB last year, we had the dealer add the Airstream solar option. That was a single 80 watt (6.67 amps) solar panel mounted on the roof. It is really nice, and we want to increase it.

I see that the solar controller is rated up to 25 amps. Since 3 panels (240 watts) at 12v is 20 amps, the controller should handle it.

However, looking at the wiring diagram, it looks like the wire from the panels to the controller is 10g wire fused at 10 amps. The wire from the controller to the battery buss is 12g wire fused at 10 amps. If we go to 3 panels, the 20 amps of charge are way too much. Even if we only go to 2 panels, the 13.34 amps is too high.

Can we bump our solar up? And if so, how high? We REALLY want 3 of those 80 watt solar panels on the roof.

Hi,

I assume you have assessed your specific needs before planning how to recharge.

I have a 2013 23FB so I think what I have seen is close to what you will face... I added 300W (3x100 Renogy) a Trimetric SC-2030 PWM controller and its companion TM-2030 monitor (with 500A/50mv shunt and assorted parts and pieces) but kept them in parallel and ran 6 AWG up to the roof. A lot of work.

First the 80 watt panel won't come close to 6.67 amps. Figure 17.7 Vmp produces about 4.5 amps (Imp), be that as it may.

The controller, breakers, and increased wiring, parts and pieces are in that forward compartment under the bed. I set it up to go to a 1000W to 2000W inverter possibly at some future date.

An option for you would be to just add two 100 W panels (giving you about 11.4 amps) which the factory 10AWG would be okay and you only need a PWM controller, or go four panels and relocated / remove / upgrade the OTR antenna... freeing up that spot for another 100W'er. By connecting two panels in parallel (2 sets) then these two sets in series the factory wiring would still be okay. This would require a MPPT such as the very good Victron and then use the Victron monitor. I am a diehard Trimetric fan, but Victron MPPT fits in this scenario.

If you thought 200 W would be enough you could go with the PWM Trimetric like I did and just use the factory 10AWG with those panels in parallel.

A third option and one that I might go with, is to stay with 300W on the roof, maybe you only staying with 200W on the roof... and add a 200W suitcase to the mix, which its flexibility in placement comes in handy when in shaded spots. The negative of this arrangement is carrying the suitcase around... even then, I think the pros outweigh the cons.

You only need a 30A Victron controller for the parallel - series setup and if using a suitcase, it would have its own controller.

The pic with the TM-2030RV is just to show you where I installed it. Hiding the wire was fairly easy to that point.

I used the curved roof mount along the outside edges and the normal ones on the inside.

You might notice I greatly increased the cabling / wiring/ sizes. And, easy to add the correct size breaker as needed. My backwards "S" (SCC breaker) while standing on my head should get a laugh.

You might notice negative battery cable to shunt isn't there yet. I had to order that one and added a few days later. Having a 16 ton crimper lets you make your own larger cables.

Let me know if I can help.
Thanks
Clint

[Bobbo]

Originally Posted by Wolfwhistle

Hi,

I assume you have assessed your specific needs before planning how to recharge.

I have a 2013 23FB so I think what I have seen is close to what you will face... I added 300W (3x100 Renogy) a Trimetric SC-2030 PWM controller and its companion TM-2030 monitor (with 500A/50mv shunt and assorted parts and pieces) but kept them in parallel and ran 6 AWG up to the roof. A lot of work.

.
.
.
.

Let me know if I can help.
Thanks
Clint

Your post is very, very helpful. Thank you. I have an unrelated question for you regarding one of the photos you posted.

The photo showing the Samlex inverter outlet above the dinette couch has me wondering. I am also (different project) going to install a 200 amp Intellitec Big Boy Latching Relay to disconnect the inverter from the batteries with the push of a button. I am wanting to install the button there. How did you route the wire for the outlet? What path did it take?

[TouringDan]

Originally Posted by Acheron2010

I'm sorta kicking this around the campfire as I figure out the optimum boondocking power supply. Rather than more roof acrobatics, I am considering the portable panels that you plug into the supplied external connection on the trailer tongue of my 2019 FC26. I can then position them throughout the day for best capture, even if the trailer is in shade. Don't yet know about capacity or even my needs - still collecting info.

I have 200 watts of portable solar, a Victron Bluetooth controller and pigtails to connect the solar panels to. The solar panels ride fine in the bed of my truck. Total cost was about &450.

Dan

[AirMiles]

Bobbo, I believe Wolfwhistle gave you great alternatives and is spot on. He has the same 23’ as you and knows what fits and the power your panels actually produce. I would follow his recommendations for a 23’.

[Fair_Enough]

I made a simple / functional drawing of what series / parallel entails and hope it clears that up for anyone interested. I didn't know where to stop and added a (-) bus and shunt. This is the specs for Renogy Eclipse* 100 Watt 12 Volt Monocrystalline Solar Panel... Sold by: Amazon.com Services, Inc. I have no dog in the fight what product or where you get it, but I like Renogy so far.

I mentioned in the other reply about drilling thru the ceiling after fishing to center between wardrobes. Another member mentioned drilling up thru the wardrobe. Doing it over I would drill thru inside that wardrobe. Away from ribs / supports / wires.
Clint / WW

[Bobbo]

Originally Posted by AirMiles

Bobbo, I believe Wolfwhistle gave you great alternatives and is spot on. He has the same 23’ as you and knows what fits and the power your panels actually produce. I would follow his recommendations for a 23’.

Oh, trust me! I have printed out what he wrote and I am studying it! I will, in all likelihood, do something almost identical to what he did.

[Fair_Enough]

Paprika is also right on the money.
Clint

[Fair_Enough]

I fat fingered the voltage drop / cable length on the drawing. While it is true the 10 AWG will work okay (series - parallel) the cable length max should be half of what I typed. Its 22 to 23 feet. I have no idea how that happened. 3% VD is a good rule for charging sources, but much more can be an issue in low light or shady situations when every tenth counts.
Sorry if I confused anyone.
Clint

[Fair_Enough]

Bobbo,
Here is the photo I tried to send on the PM
Clint

[Bobbo]

Thanks for that clarification Wolfwhistle. It really helps. For everyone else, we have been PM'ing each other with questions, answers and suggestions.

[Fair_Enough]

Bobbo, that PVC pipe runs all the way into that wardrobe. I had to use a big hole saw. I also used a reciprocating saw in the storage compartment walls where the pipe rests. Thinking about it later, I should have build a 2” x 4” chase out of plywood across there; leaving the top open. The pipe I have is full. And if I need to run anything else I’ll need another something across there.
Clint

[frank nordyk]

Originally Posted by AirMiles

I’m one of a handful of solar prewire proponents and pretty much agree with RM’s advice in this situation. You do not want three panels in parallel on the factory prewire. Too many Amps too few Volts. The “sweet spot” for a factory prewire installation is four panels in a series/parallel arrangement. You need the higher volts of the series configuration to make the prewire work. You also need an MPPT controller for the higher Volts and 6 gauge wire between the solar controller and battery (or buss bars) for the higher Amps.

The factory prewire works perfectly with my four 100W panels wired in a series/parallel configuration with a Victron 100/30 MPPT solar controller and 6 gauge wires to the positive/negative battery connections. That is the configuration I would suggest with the factory prewire.

Great timing. We live in CA, so it's sunny here a lot. We just got our 2019 Globetrotter three mos. ago with two 80 Watt solar panels. I was thinking of adding (Myself) a flex 100 watt panel. Will the current wiring be OK, and is it an over kill. Thoughts pls. I am not techy.

[Kristof]

I have done four solar installations on RV units including my truck camper - and I wish I had this thread available to me from the start! There are some folks here who really understand the variables and the choices/risks. Here are some things I learned the hard way:

Think about your batteries. All that power and the way you get it to the battery (bank) needs to be balanced with the amount of AH your battery can store and the rate at which it can charge and discharge. In my mind sometimes an investment there pays off more in the long run. How any folks are now kicking themselves for not going with two X GC2 6 Volts?

Bus bars on the roof shorten the length of the large cable runs. Sometimes the best way to find the shortest route to the battery is using wire loom and running over the surface of the trailer. If done neatly it does not look to bad.

Keep you Charge Controller close to the battery (bank).

Keep your inverter as close to the battery bank as possible.

Make sure you have a battery charger (decent one with high amps) on the inner side of you shore AC hookup. Normally the charger runs off the pre-installed panel - which your inverter may power. Think hard on this - you are then using battery to charge your battery. Just saying.

There is an automatic switch you can buy that takes in your shore AC line and the line from your inverter and then automatically uses the one that has power. Run that line to your panel - and use the inverter switch judiciously.

[Bobbo]

Originally Posted by Kristof

Keep your inverter as close to the battery bank as possible.

Make sure you have a battery charger (decent one with high amps) on the inner side of you shore AC hookup. Normally the charger runs off the pre-installed panel - which your inverter may power. Think hard on this - you are then using battery to charge your battery. Just saying.

There is an automatic switch you can buy that takes in your shore AC line and the line from your inverter and then automatically uses the one that has power. Run that line to your panel - and use the inverter switch judiciously.

You have lost me with this. Are you hijacking this thread from purely solar install to inverter powering the trailer? That should be a different thread as the two have nothing in common.

Let's try to keep this thread focused on solar please.

[rmkrum]

A well-designed solar system needs to consider more than just solar power.

Inverter, converter, monitor, and controller are all part of the system. Think system level from the top down as you engineer it. Kristof is thinking system, IMHO a darn good idea.

Just slapping more panels on top of the AS is not going to be efficient unless you also consider the rest of the parts, and how you use and manage the entire power system.

[daleyocum]

yI have 500watts of solar on the roof (and 300ah of lithium) but often that translates into just 20amps going into charging the battery due to the angle of the sun, partial shade, etc. All of us solar geeks can get pretty worked up about wire losses and such but for those not similarly obsessed I’ll bet you’d be happy with just adding up to 400watts of solar on your roof in parallel, using the 10 gauge solar prewire, and getting on with your life. If your panels aren’t all exactly the same you’d need to do that regardless.

Sure, by going to a lot of trouble you could get more efficiency with some combination of thicker wire, a series/parallel arrangement, upgraded MPPT controller, etc. I find this kind of engineering fun (I’m an engineer) but if that’s not you, don’t stress about it. If you already have some factory solar on the roof just adding another panel or two in parallel is easy and will payoff quickly.

If you are just starting out and thinking of 300 watts or less I’d just use the AS prewire, add a Victron SmartSolar 100/30 MPPT controller for around $200 (to future proof it) and see how you like it. At 400w there’s some debate on doing a series/parallel arrangement through that MPPT controller and the prewire or going all parallel and maybe upgrading to new 6ga wires down from the roof. 400w in parallel is still okay with the prewire, it’s just the losses start to become apparaent when it’s opperating at full capacity (which can be rare depending on where you camp.)

One nice thing about staying 12v parallel is you can also easily plug in an additional portable panel that you can place and aim on the ground. This can have about twice the power production of a roof panel at the expense of you having to move it around over the course of the day as the sun moves. I bring mine sometimes and sometimes not depending on where we’re going. Lot’s of trees and staying in one place for a while? Bring the portable panel.

The bottom line is at 400w or less, the first 80% of available solar energy are easy, the last 20% can cost you 80% of the work.

By the way, I’d carefully consider the lifespan of flexible solar panels. They seem like a good idea until you watch this. I went with solid glass panels for that reason.

The reason I went all parallel is I didn’t have room for 600 watts of panels and wanted more than 400 watts. You need an even number for series/parallel. I ended up running 6ga wire. The Wynn’s experiments on shading convinced me as well.

[FLOmads]

We had an appointment at Windish RV in Fountain Colorado to install the zamp panel for our 2017 FC 23fb and instead had our trailer totaled in a hail storm, no 23fb in stock so we went with a 2018 FC 25fb instead (thank you Geico!) and had 3 panels, 240 watts, installed, had a bad cell so replaced with 2 6v golf cart batteries, I find that solar is not very useful to us as full timers, we still use the generator, single Honda 2000i, and will probably add the Honda 2000i companion to run in series.
I just don’t see a value of adding solar as far as performance goes, too many days of cloudy conditions and shade trees, also the draw of charge controller etc seem to defeat the purpose. We can boondock for 5-7 days before needing more then the solar can provide.

[uncle_bob]

Originally Posted by Paprika

"#12 wire is good for 20 amps. #10 wire is good for 30 amps."

Those amperage ratings tell you how much current you can put through a wire without risk of overheating and fire, but they don't tell you how much voltage drop will occur. When you spend hundreds of bucks putting solar panels on your roof, you want to make sure you're not throwing away the power you just paid for on the way down to the controller.

Here's a sample scenario. Let's assume the total length of the wiring between panels and solar controller is twenty feet one way. (That includes the wiring between the panels on the roof--easy to overlook.) And we'll assume two 100 W 18 V panels in parallel. With #10 wire you'll lose 3% of your panels' voltage on the way down. With #12 wire, you'll lose 4.8%. (Wiring the panels in series would cut the voltage drop to 1.5%.)

That's an optimistic scenario, by the way. Depending on the length of your roof and where you mount your panels, you could easily have twenty feet of wire on the roof alone, plus whatever it takes to snake it down to the controller. Unless your trailer is very small, thirty to forty feet total may be more realistic. And if you double the wire length, you double the voltage drop.

In short, it's not just a question of what you can get away with and not start a fire. Wire gauge has a major effect on how much power is lost between the roof and the solar controller. You can easily determine this for your particular application by using an online voltage drop calculator.

Hi

Rather than depending on some flakey app, why not just do the math? It's not very hard.

Number 10 wire is 0.001 ohm per foot.

We're talking about a 23' trailer that is 7' tall inside here. Max run from the junction box to the charger is < 18'. Round trip would be < 36'

36 feet times 0.001 ohm is .036 ohms.

280W at 18V is 15.55 A

15.55A at 0.036 ohms gives you a drop of 0.56 volts.

That's 3.11% of 18V. Given that the controller is likely 80% efficient not a big deal.

Putting the three panels in series triples the voltage to 54V. It cuts the current to 5.2 A and the voltage drop to 0.19V. 0.19V is 0.33% loss.

Bob

[Dorsalis]

We also purchased a 2017 FC 23FB with which we have been mostly very happy. However, like you, we requested the solar upgrade, which consisted of an 80 Watt Zamp roof panel, which is connected to a 3 receptacle receiver box on the roof. We came across an offer on the internet for an "Airstream Solar Upgrade", which offered 2 additional 80 Watt Amp panels with plug ins designed especially for the 3 receptacle receiver box. SO, I purchased the two additional panels and installed them. Before doing this I called Airstream Technical Support and specifically asked if the Solar system (solar controller wiring etc...) could handle the extra two panels. I was ABSOLUTELY ASSURED that the circuit could handle the additional 2 panel option. I was told that the reason for the three receptacle box was specifically to allow for this option, to upgrade with another 2 80 Watt panels. However, after installing the system, a fuse under the bed mattress started blowing out whenever we had a strong sunlight. I called technical support several times about this, particularly as the trailer was still under warranty. Finally, I spoke with a technician who informed me that "...well, we don't offer a 3 panel upgrade on the 23FB as yet because we have not worked out all the bugs...". I sincerely wish they had advised me of this BEFORE I purchased and installed the additional two panels. As things stand now, I must keep two of the panels unplugged and just use one, which barely keeps up with a "Trickle Charge" for the system.

Our conclusion in all this was that Airstream is presently naive and untried in Solar Panel systems. The solar controller and wiring system they have put in on the 23FB models is entirely inadequate for anything more than an 80 Wall system. We also made the mistake of purchasing a Zamp portable solar panel system ( we were really thinking we could amp up our solar). That one also is a problem when used in combination with the existing 80 Watt panel. Once again, when we purchased the portable panel, we were ABSOLUTELY ASSURED that the Airstream was rigged to handle the extra loads. Clearly, the 23 FB is not.

Overall, we are delighted with the 23 FB in its design and function. We love the way it pulls, the small footprint for getting in to parking spaces, the overall ergonomics of the Trailer. If it were not for this Solar Panel defect, the trailer would (at least for us) be PERFECT.