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Old 09-18-2015, 02:31 PM   #15
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Mike, what was involved in relocating the Omni-directional TV Antenna to the AC Shroud? Did it just screw to the shroud with existing holes or did you have to fab some sort of bracket? I want to add a 100W panel to my 14 AI and behind the AC would be an excellent spot with only the antenna to deal with.
Thanks in advance,
Bill

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I keep reading discussions on this and other forums about house battery problems. In my view the solution is solar. Airstream is behind their competitors in increasing solar panels on the roof to at least 200 watts, which is a level that solves nearly all battery maintenance issues. Of course this also means upgrading to a better solar that the one now provided by Airstream. Since I upgraded my solar to 400 watts I never worry about my batteries, even with the refrigerator running constantly. I started with 200 watts and that was adequate to keep the batteries maintained where I park my van in half day shape behind my townhouse. I increased to 400 watts as I intend to increase my battery capacity to 400 AH so I can do more without hookups.

This solution may not help those that store their Interstates indoors.

Just my 2 cents.


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Old 09-18-2015, 07:23 PM   #16
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I located one of those on the A/C shroud almost 2 years ago. I would not do it again, as the effort required vs. installing a new Jack digital directional antenna ales it a moot point.

Much better reception with the Jack along with full digital and an integrated signal amplifier.


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Old 09-18-2015, 10:41 PM   #17
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I got the idea to mount the antenna on the AC cover from lewster. I'm not sure I'd do it again. I mounted mine slightly different then lewster. I attached it directly to the AC cover, not using the the tripod support. The main problem I've had is the top of the AC shroud is rather flexible and I've had to add some additional spacer to keep the antenna from flopping in the wind while driving.

Since I have four 100 watt panels, two forward and two aft, there wasn't much roof space left to mount any antenna except on top of the AC cover.


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Old 09-19-2015, 03:15 PM   #18
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All I want to accomplish with my AI is to be able to leave the Novacool frige on during the day when we're away from the rv during trips without running the batteries down. (I have meds that need to stay cool) Seems like a good 100w panel would accomplish that providing the wiring and charge controller are all copacetic. I have ordered a GS-100 panel from AM Solar which I was going to place where the omni-directional tv antenna is but if the experts can verify that a single 100w panel will accomplish what I am looking for I will simply replace the factory 50w panel with the new 100w panel.
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Old 09-19-2015, 03:20 PM   #19
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The Solar Solution

If you are intending to use the stock charge controller........ I'm afraid not.

For a minimal cost increase, I would use 200 watts and upgrade your solar charge controller as well to a Morningstar or Blue Sky PWM unit.

This will guarantee you enough 3-stage solar charging amps to overcome your fridge draw AND the parasitic DC loads in your AI. Your existing controller is a single stage unit which is definitely not optimal for proper battery charging.


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Old 09-19-2015, 03:36 PM   #20
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Which Morningstar or Bluesky controller would you recommed Lew?


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If you are intending to use the stock charge controller........ I'm afraid not.

For a minimal cost increase, I would use 200 watts and upgrade your solar charge controller as well to a Morningstar or Blue Sky PWM unit.

This will guarantee you enough 3-stage solar charging amps to overcome your fridge draw AND the parasitic DC loads in your AI. Your existing controller is a single stage unit which is definitely not optimal for proper battery charging.


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Old 09-19-2015, 05:30 PM   #21
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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?
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Old 09-19-2015, 05:59 PM   #22
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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!
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Old 09-19-2015, 06:12 PM   #23
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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......
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Old 09-19-2015, 06:22 PM   #24
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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.
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Old 09-19-2015, 11:16 PM   #25
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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.
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Old 09-19-2015, 11:44 PM   #26
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Quote:
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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 77F (25C) 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!
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Old 09-19-2015, 11:51 PM   #27
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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.
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Old 09-20-2015, 03:02 AM   #28
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Basic DC electricity...

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
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