Solar Panel Installation Report

[flygrrl]

Originally Posted by masseyfarm

There is always a problem/start point, and from there you keep refining the solutions.!




"Massey, I read your post twice and your three bank set-up just made my brain turn to sauce. LOL! "

Masseyfarm, maybe it's a Canadian thing, I TOTALLY get it. Brain is always working, how can I make this better, and do more?

[steverino]

Update: we got a little experience with our system this week while camping without hookups at Seacliff; the solar panels performed very well. Despite having a marine layer linger until at least noon, as well as loosening up a bit on energy conservation habits, the batteries were fully charged each day by the time late afternoon arrived. The system put 70 to 75 A-Hrs of power into the bus every day. Also fun to see was during daylight, when turning on a load such as a fan - the current output of the controller would jump up by an amp or two, showing that our daylight consumption was satisfied entirely by solar - thus saving energy stored in the batteries for evening and night.

[barts]

In terms of what happens when multiple charge controls are active at once, as far as I can tell it works like this:

1) Truck alternator charges to about 13.6 V... if no sun, batteries charge (slowly due to long wire length) to 13.6 volts.

2) Solar control is typical set to about 14.2 volts. If the sun shines, the trailer batteries charge to 14.2 volts.

3) If I'm plugged in and the sun is shining, we get to about 14.2 volts on the solar. If we're low the converter gets us quickly to 13.2 volts; the solar does the rest.

The way it works is that each charging source seems to charge to it's set point, but doesn't prevent another source for raising the voltage higher.

- Bart

[masseyfarm]

If your alternator only puts out 13.6V and you are running through an isolator, you are lucky if you squeeze 13V out at the trailer battery.

On my battery bank #1 (chassis) my small 7A charge controller, it has LED display that shows:
1) charging, and 2) charged.
When my Delco 160A (recently upgraded from 130A) is running, the charge controller on that bank will show CHARGED.
That is why I have installed a solenoid and manual control so I can direct this panel to battery banks #2 & 3 while traveling.
Now, that said, I am running this HD alternator and the battery bank is located within 5'. This 40W solar panel is located within 12'.
When I tie in battery banks 2 & 3, the alternator does not run through an isolator, with the typical loss of .8V, but runs through a SurePower 1315-200 which allows full juice both ways.
Another factor specific to my application, is most of my experience is north of P45 and solar may not be quit as effective.
Dave

Originally Posted by barts

In terms of what happens when multiple charge controls are active at once, as far as I can tell it works like this:

1) Truck alternator charges to about 13.6 V... if no sun, batteries charge (slowly due to long wire length) to 13.6 volts.

2) Solar control is typical set to about 14.2 volts. If the sun shines, the trailer batteries charge to 14.2 volts.

3) If I'm plugged in and the sun is shining, we get to about 14.2 volts on the solar. If we're low the converter gets us quickly to 13.2 volts; the solar does the rest.

The way it works is that each charging source seems to charge to it's set point, but doesn't prevent another source for raising the voltage higher.

- Bart

[eheffa]

Originally Posted by barts

In terms of what happens when multiple charge controls are active at once, as far as I can tell it works like this:

1) Truck alternator charges to about 13.6 V... if no sun, batteries charge (slowly due to long wire length) to 13.6 volts.

2) Solar control is typical set to about 14.2 volts. If the sun shines, the trailer batteries charge to 14.2 volts.

3) If I'm plugged in and the sun is shining, we get to about 14.2 volts on the solar. If we're low the converter gets us quickly to 13.2 volts; the solar does the rest.

The way it works is that each charging source seems to charge to it's set point, but doesn't prevent another source for raising the voltage higher.

- Bart

This would fit my observations of our system as well. Each device has its own set point but can contribute in tandem if the batteries are below the threshold for each 'Charger'.

-evan

[rodsterinfl]

I just found this thread and although it is older, wanted to subscribe. I am looking for where to place my controller. I do not know if advice has changed since 2010 and this thread's beginning but the solar company people (three different companies) are telling me that the controller needs to be within 5-6 feet of the battery run- CLOSE to the battery bank. I have a front sofa model with little cabinet in the front. My only cabinet is right against the wall by the fridge and also the solar prewire. That area makes the most sense BUT it is more like 8 feet from the battery using the 10 awg battery prewire. Thoughts?

[eheffa]

Originally Posted by rodsterinfl

I just found this thread and although it is older, wanted to subscribe. I am looking for where to place my controller. I do not know if advice has changed since 2010 and this thread's beginning but the solar company people (three different companies) are telling me that the controller needs to be within 5-6 feet of the battery run- CLOSE to the battery bank. I have a front sofa model with little cabinet in the front. My only cabinet is right against the wall by the fridge and also the solar prewire. That area makes the most sense BUT it is more like 8 feet from the battery using the 10 awg battery prewire. Thoughts?

I doubt there is an absolute cutoff for this distance from the controller to the batteries. The main limitation would be voltage dropout or resistance over a long run. If you are concerned that you are pushing the limits here, make that run in 8 AWG or even 6 AWG wire... (Maybe the Lewster could render his opinion. I recall that he thought the factory pre-wire gauge wiring was too light so I didn't use it.)

-evan

[lewster]

Originally Posted by eheffa

I doubt there is an absolute cutoff for this distance from the controller to the batteries. The main limitation would be voltage dropout or resistance over a long run. If you are concerned that you are pushing the limits here, make that run in 8 AWG or even 6 AWG wire... (Maybe the Lewster could render his opinion. I recall that he thought the factory pre-wire gauge wiring was too light so I didn't use it.)

-evan

Here is a chart from Blue Sky Energy stating their requirements for wire gauge
at differing run lengths. You will notice that for a 36 cell panel, which is what most of you are using, the effective length of 10AWG is 10.2 feet! This is why I suggest using 6AWG or 4AWG, depending on the size of the solar array for the desires 3% maximum voltage drop.

And ALWAYS connect your solar charge controller directly to your batteries. (Sorry about the orientation. The phone had a mind of it's own!!!)

[rodsterinfl]

Isn't the wire gauge related to the amperage amount too? I am looking at 150 watts of panel with about 9 amps total.

[eheffa]

Originally Posted by rodsterinfl

Isn't the wire gauge related to the amperage amount too? I am looking at 150 watts of panel with about 9 amps total.

Yes, your anticipated current requirements will influence your choice of wire size. Lewster's posting above should give you the information you need. If you think you might ever want to add panels or capacity, I would err on the side of too big rather than too small.

-evan

[rgwatkin]

Great job, but not an easy one to be sure. I was fortunate enough to accidentally walk into an Airstream Shop before I purchased my 2012 28ft FC and seeing the effort that went into retrofitting solar onto a trailer. That was a "I've seen God" moment and I knew factory solar was a must. I didn't know it at the time but in 2012 the trailers came with a solar pre-wire as std. equipment. The cost for my two panels from the factory (installed) was $2950.

[rodsterinfl]

Yes, I understand that there is a relation but I was concerned over the 10' limit on a particular gauge without the amperage part.

Here is something I found to be helpful:

American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies and wire breaking strength

It is a chart that gives resistance rating, diameter of wire, gauge, and power transfer rating then provides a calculator for applying it to length of wire for an application.

[alano]

Originally Posted by rodsterinfl

I just found this thread and although it is older, wanted to subscribe. I am looking for where to place my controller. I do not know if advice has changed since 2010 and this thread's beginning but the solar company people (three different companies) are telling me that the controller needs to be within 5-6 feet of the battery run- CLOSE to the battery bank. I have a front sofa model with little cabinet in the front. My only cabinet is right against the wall by the fridge and also the solar prewire. That area makes the most sense BUT it is more like 8 feet from the battery using the 10 awg battery prewire. Thoughts?

I'm a big fan of using the existing solar pre-wire. Since your system is only delivering 9 A and you're thinking of adding an additional 16 feet, 8 feet per conductor of 10 gauge wire, the additional loss will only be 9 A * 16 ohms/1000 ft = 0.15 V. I'm assuming that you're describing a single panel system where the panel is rated around 150 W. This means the additional wires adds an additional loss of less than 1% to your existing wiring losses.

10 gauge wire is more than sufficient to carry 9 A. Even better, if you choose to add additional panels (same size hopefully), then add them in series and use a MPPT solar charger. This way the current stays the same and your losses are halved!

[lewster]

Originally Posted by rgwatkin

Great job, but not an easy one to be sure. I was fortunate enough to accidentally walk into an Airstream Shop before I purchased my 2012 28ft FC and seeing the effort that went into retrofitting solar onto a trailer. That was a "I've seen God" moment and I knew factory solar was a must. I didn't know it at the time but in 2012 the trailers came with a solar pre-wire as std. equipment. The cost for my two panels from the factory (installed) was $2950.

Interesting observation. I can show you dozens of photos of properly installed solar charging systems that run rings around anything the factory does, along with the same number of 'rat's nest' wiring jobs straight from the factory that I have corrected and re-installed the way they should have been done on assembly!

Once you get much over the 100 watts that the factory installs with their minimal 10 AWG wire in extra long runs, along with the totally incapable matchbook sized solar controller, I'm afraid that they are out of their league.

[Gene]

I agree with lewster and will add the factory overcharges for the systems they install. So do some dealers. I, even more ignorant when we bought the trailer than I am now, had the dealer put on a 100 w. unit. The dealer was so dumb they didn't even know there was a factory installed 10 awg cable and installed a second cable. The unit they installed only lasted a few years and by then the company that made it had gone bankrupt, so the warranty was worthless.

That's when Lew showed up (we offered food, something Lew appreciates, though it hasn't worked since) and we spent a day troubleshooting the dealer system, finally realizing it was a piece of crap. Lew put in a new system and all is well. 200 watts and it cost less than the factory system (even with the food).

The prewired 10 awg cable has been installed for a long time now—ours had one in 2007, and it had been done for some years before.

Gene

[lewster]

Did someone say.......FOOD '!?!?!?!?


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

[rodsterinfl]

10 gauge wire is more than sufficient to carry 9 A. Even better, if you choose to add additional panels (same size hopefully), then add them in series and use a MPPT solar charger. This way the current stays the same and your losses are halved!

That is why I like the forum because you hear various sides and it helps when doing a project. I have been scouring info on RV solar and there is a lot written on wire gauge- to go bigger. One write-up I found said to go 2-3 sizes bigger than needed. I kinda believe that is what I am doing using the factory wiring. It is 10 gauge right? According to the AWG rating for 10 gauge, it is rated 15 amps for power transmission. The second concern is length (compute loss) as you mention Alano. If I am correct, I am looking at around 12' of connector cable to the factory wires and guessing 6-8' for the factory run to the controller. The controller is really close to the battery which I read is what you want. So, it looks to be around 20' for wiring. By the chart I am exactly 2-3 sizes bigger than needed with my panel. Now a 250 watt system would add length and also take it to the max rating- not recommended from writings. I would think that 200 would be more a stopping point with factory wiring by the chart anyway. The Morning Star monitor and controller are hopefully good ones. I read they were but I guess time will tell. The way I am going about this with a suitcase/controller, a front panel/controller and roof panel/controller is different but I gain flexibility even if it requires manual tracking of the first two.

[alano]

The factory wiring is #10 AWG. The 15 A power transmission limits are by all accounts very very conservative and do not represent hard and true limits. In my opinion it's better to calculate your losses and decide if they are acceptable to you.

I installed at 400 W system using the #10 AWG solar pre-wiring. I was able to do this by connecting the panels in a series/parallel configuration. This requires the use of a MPPT solar charger. With this setup the current is only 10.6 A and the voltage is 37.8 V. The resistance loses due to the pre-wires in this configuration is less than 2%!

It's a good idea to install a disconnect switch between the solar array and the solar controller as well as fuse the positive connection from the solar controller to the battery.

Good luck with your system.

[RaymondFitz]

I'm looking at using the pre-wiring on my 23D since I'm only going to be adding 2x100 watt panels. Would I still need to drill a hole in the roof? I know the wire is in my fantastic fan in the rear. The 23D doesn't have a fridge vent on the roof it's on the street side. Also, planning on using the Renogy flexible panels. I do plan on upgrading to Lithium at some point in the vary near future. Could you recommend a controller that would work with my standard group 24 batteries now but would also handle Lithium after that?

Thank you,

Ray

[rgwatkin]

I currently have (2) factory 53 watt panels on my 28ft FC. I would like to upgrade to something more like (2) 100 watt panels. Does anyone have an estimate what it would cost me to have this done, parts+labor. I live in Calif.