The Solar Solution

[c21]

Looking at AM Solars basic controllers seems like the Sun Charger 30 PWM or the Sunsaver 20L would both work. Looks like the 30 PWM has an optional temperature sensor. Which would you recommend for my installation with two GS-100 Panels and would either of these allow the use of my existing Atkinson remote display?

[AtomicNo13]

The sun saver 20 is a not so basic temp compensated controller. It will happily handle 20 amps. It's a steal at less than $100 online. It's a bulletproof, set it and forget it type deal!

[arktos55343]

From what I have read up on solar charging, I believe a remote temp sensor is important for the long term health of your batteries. Charging creates heat...heat damages batteries. And if your batteries are in an enclosed space...heat is an issue with constant solar charging. You want to know what is going on. Also, it is my understanding that a higher amp controller is preferable over a lower, as you want to get the power generated by your solar panels into your batteries as efficiently as possible. A higher amp controller has more 'push' to get the energy into your batteries. I was originally going to go with a 30amp unit, but changed my mind for a 45amp unit. I will be starting off with 2 100w panels...maybe going as high as 4, when I upgrade my battery bank. And I went with the Morningstar TriStar 45 (PWM).

Other's opinions may vary......

[AtomicNo13]

The temp sensor is primarily used to change the voltage when the temp differential is 10 degrees or more between the batteries and the controller. It artificially compensates its voltage trim as to not over voltage the batteries, charging a very cold battery is just as taxing as charging a very hot battery.

[73shark]

I keep reading all of these posts in different threads regarding chargers, solar charge controllers, temp. sensors, and solar panel size and marvel at my meager 50W panel, Tripplite single stage, and five year old OEM batteries that will run my fridge overnite and still be over 50% in the morning.

[lewster]

Originally Posted by arktos55343

From what I have read up on solar charging, I believe a remote temp sensor is important for the long term health of your batteries. Charging creates heat...heat damages batteries. And if your batteries are in an enclosed space...heat is an issue with constant solar charging. You want to know what is going on. Also, it is my understanding that a higher amp controller is preferable over a lower, as you want to get the power generated by your solar panels into your batteries as efficiently as possible. A higher amp controller has more 'push' to get the energy into your batteries. I was originally going to go with a 30amp unit, but changed my mind for a 45amp unit. I will be starting off with 2 100w panels...maybe going as high as 4, when I upgrade my battery bank. And I went with the Morningstar TriStar 45 (PWM).

Other's opinions may vary......

This is not an opinion, but a basic declaration of solar fact:

" A higher amp controller has more 'push' to get the energy into your batteries."

I have no idea where you read this, but you simply can't get more amperage from a PWM controller than the maximum output value of your solar array.
The increased excess amperage of a controller is not worthwhile if you don't have the solar array to support it. Controllers don't provide amperage out of thin air. An MPPT controller WILL provide 'solar boost' by utilizing the panels' excess voltage 'headroom' to increase the charging amperage that the batteries see by up to 30%, but you need the right sized solar array to begin with.

400 watts, especially with a PWM controller, will only give you around 20 amps maximum around solar noon with a clear sky with the sun perfectly perpendicular to the panel surfaces to capture maximum solar radiance at the panels. As you have chosen a PWM controller, you will never see more than this 20 amps to the batteries since there is no MPPT function to boost your amperage, regardless of how much capacity your controller has. Even if you did have an MPPT controller, you would still never see 45 amps from a 400 watt array, more like a 25 amp maximum. Your 45 amp controller will come in handy IF you decide to increase your solar array to 800 watts, but you could have easily used a 30 amp controller and gotten the same results at a lower cost.

With respect to temperature compensation, look up any temperature compensation curve and you will see an almost inverse linear relationship between battery temperature (measured at a battery negative terminal by a lug type sensor screwed down to the terminal) and charging voltage. At higher ambient battery temperatures, they require less charging voltage than at 77ºF (25ºC) which is the standard charging baseline.

Lower battery temperature requires more charging voltage to do the same job when compared to the baseline voltage.

But as we all know.........if it's on the internet.....it MUST be true!

[lewster]

Originally Posted by c21bill

Looking at AM Solars basic controllers seems like the Sun Charger 30 PWM or the Sunsaver 20L would both work. Looks like the 30 PWM has an optional temperature sensor. Which would you recommend for my installation with two GS-100 Panels and would either of these allow the use of my existing Atkinson remote display?

If it were my coach, I would use the Sun Charger 30 PWM as it has an integrated display that will provide you with useful information about your battery voltage and charging amps. This will replace the display of your present Atkinson unit.

The Morningstar Sunsaver L is also a good unit but has no display and is not compatible with your Atkinson display unit.

[cwbiii]

E=IR, voltage (E) = current (I) times resistance (R)
W=EI, watts = voltage times current.

So if your battery needs a minimum of 14 volts to charge
and your 100w solar panel puts out its maximum current at 15V
W/V = I
100/15 = 6.6 amps

100/14 = 7.1 amps

The difference is .5 amp which is discarded or lost by anything but a MPPT controller. The MPPT is a DC-DC converter which operates your solar panel at its optimal point and converts the voltage to the battery optimal charging point.
Exactly how it does this is a bit complicated, (and I could explain it but I don't want to bore you) but it can do it quite efficiently so it converts most of that otherwise wasted energy back into useful energy for your battery.
Those 2 voltages used in the example above are moving all the time due to solar conditions and battery conditions. The MPPT adjusts itself many times a second in order to stay in the optimal point. That is what Maximum Point Power Tracking means.
The larger the difference the less efficient a "standard" controller is.

Also since we have pretty much determined that the maximum output for a 100 w panel is 7 amps or less then a 20 amp controller will handle up to 3 100 amp panels without throwing away anything that is not a mismatch between solar panels output and batteries input. A MPPT controller will only handle 2 100w solar panels before throwing away some energy...
My 20amp versions start discarding at 260W.

As you all pretty much understand already real estate for solar panels on RV's is in short supply so getting the most out of what you've got is a pretty high priority. Wasting is not a particularly good choice, especially if you do the cost analysis for adding another panel or changing the controller to a more efficient one. Yes it does cost more, but not a lot more.
Airstreams add the wrinkle of a curved roof which puts the panels at different angles. The difference in mine is 30 degrees, and that difference can easily have one creating half the energy of the other under identical conditions other than the difference in angle. Directly overhead is the only time they are essentially the same... and I have a max of 377/400 to date for that. 94% max efficiency is pretty good. 3.5 to 4X my solar array size is what I seem to be able to store in my batteries on a good day if they are in need of replenishing from recent use.

Chuck

[UKDUDE]

Originally Posted by 73shark

I keep reading all of these posts in different threads regarding chargers, solar charge controllers, temp. sensors, and solar panel size and marvel at my meager 50W panel, Tripplite single stage, and five year old OEM batteries that will run my fridge overnite and still be over 50% in the morning.

I'm currently on a cross-country trip with my wife. We still have our measly 50W panel and the Magnum; our fridge is stocked and running and my wife likes to look at the TV when we stop for the night - all dry camping. By the morning the batteries are down to 65-60%. So we're happy. I think it's down to always taking care of the batteries from new.


Sent from my iPhone using Airstream Forums

[toskeysam]

Small victories build up. I finally got the 100 watt Grape Solar panel installed to replace the 50 watt panel. I used AM Solar's tape-down feet, combiner box, and 15" tilt bars. I reinstalled the in-line fuse holder in the new combiner box. Installed the fuse and......Wow! What a difference! Instead of straining to see 2.7amps from my old 50 watt panel, it immediately went to the full rated amperage (5.5amps). Still need to put Sikaflex on various places, but enough roof time for one day.....golf clubs are calling.

Next step will be to add another panel, replace Atkinson controller, and re-wire as needed.......next year.

Switching gears toward more storage space by removing second row seats for now......


Sent from my iPad using Airstream Forums

[toskeysam]

A couple pics of my 100 watt panel upgrade. I did have to add an extension to lift the panel above the bathroom vent. Decided to go ahead and drive screws into the feet/roof, in case the extra torque on the tape made it release.


Sent from my iPad using Airstream Forums

[Easyrider06]

Looks like a neat job with the 100 watt set-up. We have a new-to-us 1989 Excella and would like to add solar to the unit. Is that something that certain year AS's were pre-wired for and added if the option was selected? If so, what indicators would we look for and wire into? If not any recommendations for solar add-on kits on the market? Thanks...
James and Rebecca

[Boxster1971]

In my view the best source for RV solar systems is AM Solar in Oregon. They offer complete kits that have everything including wiring labels. I used their products to upgrade my Interstate solar to 400 watts.
http://www.amsolar.com


- - Mike
2013 Lounge EXT on 2012 Sprinter

[toskeysam]

AM Solar is definitely tops. While I was installing my 100 watt panel, I had two more panels and controller kit ordered and on their way. Next project for me...

[k9jackie]

I would really like to get a 400 watts upgrade but I'd have to get it installed for me... I imagine is it quite expensive and I can't see making a big upgrade like that before I pay off the spaceship but it would be nice. Solar is the way to go.

[c21]

http://www.airforums.com/forums/atta...1&d=1450651236

Here is a pic of our electrical cabinet after our solar upgrade. Bottom left is charge controller which replaced OEM Atkinson Remote Indicator. To the far right is new Magnum Remote Control which replaced the original Magnum ME-RC using a surface mounting bracket. To left of Remote Control is interior propane switch. We increased solar to 200W and replaced batteries with Lifeline CT4 6V batteries which increased capacity by 37.5%. Solar upgrade is the best mod we have done to our RV and we should have done it a long time ago.

[Boxster1971]

Originally Posted by c21bill

http://www.airforums.com/forums/atta...1&d=1450651236



Here is a pic of our electrical cabinet after our solar upgrade. Bottom left is charge controller which replaced OEM Atkinson Remote Indicator. To the far right is new Magnum Remote Control which replaced the original Magnum ME-RC using a surface mounting bracket. To left of Remote Control is interior propane switch. We increased solar to 200W and replaced batteries with Lifeline CT4 6V batteries which increased capacity by 37.5%. Solar upgrade is the best mod we have done to our RV and we should have done it a long time ago.

Nice job! Yes - a few 100 watts of solar solves a lot of the Interstate weaknesses. Just wish Airstream would figure it out and get the solar to at least 200 watts with a good controller.


- - Mike
2013 Lounge EXT on 2012 Sprinter

[lewster]

Originally Posted by Boxster1971

Nice job! Yes - a few 100 watts of solar solves a lot of the Interstate weaknesses. Just wish Airstream would figure it out and get the solar to at least 200 watts with a good controller.


- - Mike
2013 Lounge EXT on 2012 Sprinter

Airstream need a lot more than a couple hundred watts and a better controller. These are shots of their idea of an 'upgrade' on the new Interstates. Based on what I saw during MY upgrade of this coach, Airstream was better off leaving the single 50 watt hard panel where it was rather than using Go Power's flex panel. There are simply too many things wrong with this installation to detail!!

[c21]

Originally Posted by lewster

Airstream need a lot more than a couple hundred watts and a better controller. These are shots of their idea of an 'upgrade' on the new Interstates. Based on what I saw during MY upgrade of this coach, Airstream was better off leaving the single 50 watt hard panel where it was rather than using Go Power's flex panel. There are simply too many things wrong with this installation to detail!!

Wow, that looks pretty cheesy. Don't think I'd want that on my coach. Looks like they also relocated the tv antenna?