Solar regulator connection points

[airstreamz]

Hi, we are planing to get 2 x 140 watts flexible solar panels connected to our 2010 Flying Cloud. It's solar prewired, with one end near top vent, and terminate under the bed (green and yellow wires).

This is what it looks like:


I would like to ask to see what is the best way to connect the regulator to the battery? Do I connect the positive and negative wires to the terminal bus or will I need to pull new cable to reach to the battery outside?

Thanks for your advice!

[rmkrum]

If you are talking about the AS prewire, it's not big enough wire to do the job right. I abandoned mine. Search for threads by 'Lewster' for more information. He's the guru for solar systems.

I pulled in new, much heavier wire we got with our kit from AM solar. We connected the heavy cable from our charge controller which we custom mounted in the end of an overhead cabinet next to the closet. Cane from array also came through the closet from the roof junction box we added. The negative output of the charger ran to the ground buss and the positive goes through a fuse to the battery side of the main disconnect solenoid. This way the solar charger always can charge the batteries even if use/store switch is in 'store'. This also means the solar charger voltmeter lets me know how the batteries are doing.

Once you get it installed, you will never regret it--my batteries stay nicely charged as long as the sun shines for a few hours a day. Beats the heck out of the cheap Parallax charger that come with the AS from the factory. There are lots of threads on that as well....


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[airstreamz]

Looks like I will need to use the solar prewire, as there is no roof vent on my Flying Cloud to feed new heavier cables through... the prewire is I beileve 10 gauge, and should handle up to 25 amps at 9 ft long. I will then connect the 12v solar regulator to the pos and neg wires coming from the battery converter at the buss terminals, and it should work ok I hope...
Has anyone had any problems using the solar prewire the yellow and green at all?
Is it better to connect the solar regulator directly to the battery? or connecting to the pos and neg buss terminals will be fine? Thanks!

[lsbrodsky]

A lot of people comment on the inadequacy of the factory solar and I suppose in terms of maximum capability, that is true. But, my factory system works very well at keeping the batteries charged up, though I admit I do not stress the system as we are not boondockers. Plus I have a propane generator if I need it. The factory system uses your prewire and is connected to the bus, not directly to the battery, but it is on the battery side of the solenoid so that the solar system always charges, regardless of "store-use".
Larry

[lewster]

If you are looking to obtain the maximum voltage and hence, maximum amperage from your solar charge controller to your batteries, 10AWG for 280 watts of panels will be insufficient. Will it work.......sure. Will you get all the output that you are paying for............NOPE!

Airstream has a habit of running their solar wires in circles and into strange places, so what appears to be a 9' run might actually be double that (I have encountered this on multiple occasions). And 25 amps is fine for 10AWG for a 5-7% voltage drop. I will tolerate no more than 2% or less, which is one of the reasons that the 10AWG wire is insufficient.

We (AM Solar) typically spec. a minimum of 8AWG for up to 200 watts, 6 AWG up to 400 watts, and 4 AWG to 700 watts. Anything larger gets parallel systems. Note that these are for a maximum wire length of 20 feet. Anything longer gets the next larger cable size, where we use up to 2 AWG for long runs in the larger systems.

The next problem is the connection points. To maximize your output from the charge controller, it should be placed as close to the batteries as physically possible and should also be connected DIRECTLY to those batteries with the same size cables that connect the solar array to the charge controller. Every connection point is an area of induced voltage drop and will negatively affect the efficiency of your system.

An issue not usually discussed is the actual output of flex panels. I have 5 X 100 watt flex panels on the roof of my Sprinter service van. These replaced the same array of rigid panels as a test to actually see how they work. The results are a bit disappointing. While they will keep my 200 amp/hour lithium battery bank well charged, their output is significantly less than what i had experienced with my rigid panels.

This is especially evident in low light conditions like the times outside 'solar noon' which is generally 10:00-2:00. Overall, I would say the the flex panels operate at 60-70% of the actual output of a similar rigid panel. In low battery/full charge situations, my rigid panels would give me up to 35 amps at solar noon when needed. I have never seen more that 25 amps from the flex panels in the same situations. THAT is a significant difference! As always.........YMMV!

[rmkrum]

The above is exactly why I'm so totally satisfied with my kit from AM Solar. All the wiring was sized properly and I flat don't get excess voltage drops. I checked.

I ran the most direct route from the roof box and controller, and had wire left over. When I needed a replacement temperature sensor for my older system they had the part. It shipped fast and fit perfectly. Good folks to deal with.




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[KenS]

Isbrodsky's comments are worth considering - that's what we did with a system provided by AM Solar. After consulting with AMS, it was agreed the factory solar prewire should be adequate and it has been. Part of the reason was the relatively short wire distance. The other was our relatively modest 19ft AS power needs - everything is high efficient 12v - no inverter needed (although we have one). Plus, we could always change the wiring later if needed.

We've had the system for almost four years now and it has met all our power needs and been trouble free and maintenance free - one of my most successful projects. We often travel on the west coast and camp in state parks without hook-ups, including several with other family and the grandkids where the AS serves as base camp. Electrical power is never a problem, but water & waste tanks are a challenge at times.

Lewster is right - the size of the wires is important. But in our experience, the quality of the solar panels, charge controller, and batteries as well as the use of efficient 12v devices all offset the benefit of upgrading the factory prewire.

~ Ken

[lewster]

Agreed.........up to a point! 100, and maybe 200 watts would work on the factory pre-wire, as long as you use a quality controller and wire it properly......which means DIRECTLY TO THE BATTERIES.

I would still re-wire anything over 100 watts with a cable run over 20 feet.


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