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Old 12-16-2014, 11:32 AM   #1
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Do I need a Solar disconnect ?

We are brand new to the Airstream world, not to mention that this is our first rv ever. We bought a 2015 25FB International Serenity. Enjoying it to the max!

I'm planning to do a solar install and while doing my homework have read and perused all the available wiring diagrams. None of them seem to reflect a solar panel disconnect. My scenario is this: your dry camping and the solar system is charging the batteries. You then move to a camp site where shore power is available. The converter then takes over the job of charging. If there is no manual disconnect for the solar; are the converter and the charge controller working together or does one or the other sense that it is not required and shuts down the charging function?

I hope this makes some sense and someone can shed some light on how the system functions.
Regards,
Mark
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Old 12-16-2014, 11:37 AM   #2
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Originally Posted by Grezdlitn View Post
We are brand new to the Airstream world, not to mention that this is our first rv ever. We bought a 2015 25FB International Serenity. Enjoying it to the max!

I'm planning to do a solar install and while doing my homework have read and perused all the available wiring diagrams. None of them seem to reflect a solar panel disconnect. My scenario is this: your dry camping and the solar system is charging the batteries. You then move to a camp site where shore power is available. The converter then takes over the job of charging. If there is no manual disconnect for the solar; are the converter and the charge controller working together or does one or the other sense that it is not required and shuts down the charging function?

I hope this makes some sense and someone can shed some light on how the system functions.
Regards,
Mark
You do not need a disconnect on your solar charging system. All you need is a blocking diode, to prevent your shore power from back-feeding power the wrong way through the solar charger. On edit— The solar charge controller may already have a blocking diode built in. Check this before you add another one to the circuit.

As soon as you hook up shore power, your solar controller will sense the shore power's charging voltage as a full battery, and quit sending power to the battery.
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Old 12-16-2014, 12:08 PM   #3
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Thanks !

Thanks for the rapid response. I surmised this was how the system functions but needed a little confidence boost !
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Old 12-16-2014, 01:26 PM   #4
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All solar charge controllers block reverse current to prevent back flow from the batteries to the panels. They also only can charge a battery when the voltage is low enough, so when the converter/charger, or any other charge source is available they will shut down automatically. No need for a disconnect.
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Old 12-16-2014, 02:24 PM   #5
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All solar charge controllers block reverse current to prevent back flow from the batteries to the panels. They also only can charge a battery when the voltage is low enough, so when the converter/charger, or any other charge source is available they will shut down automatically. No need for a disconnect.
Thanks for the confirmation that the solar charge controller already includes a blocking diode. I thought it might, but wasn't sure.
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Old 12-16-2014, 02:55 PM   #6
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There's a catch.

The stock Airstream charger/converter is a single stage battery charger that does not reduce the charging voltage (as a good battery charger would) after the batteries are fully charged. This constant high voltage will shorten the life of your batteries dramatically.

There are two solutions possible.

Replace the stock converter with a quality multi-stage charger/converter that properly charges the batteries. About $250 for the replacement part, and fairly easy to do, or

Disconnect the battery from the charger/converter by putting the Battery Disconnect switch (by the doorway) in the STORE position. The batteries will still supply all the 12 vdc for the Airstream, be recharged by the solar panels each day, but will be (safely) isolated from the (nasty) factory charger /converter.

BE SURE to put the Battery Disconnect back into the USE position when disconnecting from external ac power, or the batteries will not power the things you need such as interior lights, refrigerator, and such.

Whew, hope I have this right. Anyone can confirm or correct it?


.
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Old 12-16-2014, 03:37 PM   #7
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Mark, I'm getting ready to do solar on my 2003 34 S/O. I'm not sure where to start on the research. Do you have some suggestions? Most of the things I've read lead me down the author's rabbit hole for a sale. I need some sizing information and the technical installation stuff too. I'm thinking it will be a DIY project. Any help from anyone else would be appreciated. I may start a new thread. Don H.
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Old 12-16-2014, 04:37 PM   #8
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Quote:
Originally Posted by dkottum View Post
There's a catch.

The stock Airstream charger/converter is a single stage battery charger that does not reduce the charging voltage (as a good battery charger would) after the batteries are fully charged. This constant high voltage will shorten the life of your batteries dramatically.

There are two solutions possible.

Replace the stock converter with a quality multi-stage charger/converter that properly charges the batteries. About $250 for the replacement part, and fairly easy to do, or

Disconnect the battery from the charger/converter by putting the Battery Disconnect switch (by the doorway) in the STORE position. The batteries will still supply all the 12 vdc for the Airstream, be recharged by the solar panels each day, but will be (safely) isolated from the (nasty) factory charger /converter.

BE SURE to put the Battery Disconnect back into the USE position when disconnecting from external ac power, or the batteries will not power the things you need such as interior lights, refrigerator, and such.

Whew, hope I have this right. Anyone can confirm or correct it?


.
The poor quality converter/charger will not affect the solar system at all, other than shortening the life of the batteries.

The Use/store switch disconnects the batteries from the interior loads (other than the propane detector and the factory inverter).

When it is in Store, and 120v power is connected, the converter/charger will still power the interior 12 volt stuff, not the battery. The converter/charger will not charge or over charge the batteries. When it remains in Store, and the power is disconnected from 120 v nothing 12 volts will work. (other than the propane detector and factory inverter).

When the switch is in Use position and the power is disconnected from 120 v, the battery will supply the 12 v power. When the switch is in Use and power is connected to 120 v the converter/charger will supply power to the interior 12 volt things as well as charge (and overcharge) the battery.

And yes, it is all very confusing. Also, if you have an older Airstream with a battery disconnect switch behind the front couch it may work differently. And if you have a still older one with no switches there are other things which happen.

Is it any wonder that people kill batteries without knowing it quite often?
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Old 12-16-2014, 05:33 PM   #9
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I guess I'd better start at the beginning. The first thing I did was upgrade to a Boondocker 60 amp converter in an attempt to extend battery life and usefulness. Took about 1 hour to complete and seems to work very well.
( Bought it from Bestconverters.com).
The second project was to install a Trimetric battery monitor ( also from best converter.com ). No affiliation, just well spoke of here on the forums.
I located the factory solar prewire ends and cable and bought equipment capable of utilizing the number 10 and rj45 signal cables. Not the most expensive gear but good performance reviews on the web.
I'll post more and attempt a picture to let folks know how I'm making out.
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Old 12-16-2014, 09:24 PM   #10
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You have good equipment now, and with a good charge controller on your solar system you will complete about all you need (other than maybe more battery capacity, like two 6 volt golf cart type batteries in series). It will all work to gather just fine, and the three charting systems (converter/charger, solar and tow vehicle) will each provide power as needed, and when needed to your batteries.

Airstream should have a "boondock" option, which has all of the stuff you (and I) have added for great off grid camping. I would swap it in an instant for all the Television, DVD, sub woofer and so on that is standard, and I never use. Those who stay in campgrounds all the time don't need it or want it, so we could have a campground camping vs. boondock camping option. The only time my Airstream has been plugged into grid power is at home. I have not been in a hookup campground yet, two full seasons of camping.
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Old 12-16-2014, 10:44 PM   #11
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When it is in Store, and 120v power is connected, the converter/charger will still power the interior 12 volt stuff . . .
From your earlier post. I think the factory solar system in our 2012 FC 25 works differently than this. When on external power and the Battery Disconnect is in STORE, overnight with no solar power available, the batteries will gradually lose power as we use 12 vdc equipment.

They are losing power the same as when boondocking without external power. They will remain slightly low in voltage until sunup in the morning, when they will began to recharge.

I believe this is because the Battery Disconnect switch isolates the charger/converter and also all the 12 vdc system from the batteries, leaving operation and recharging of the 12 vdc system and batteries entirely the task of the solar system.
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Old 12-17-2014, 12:05 AM   #12
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I don't have the factory solar package, just the one I self installed. But it is directly connected to the batteries, apparently the same way yours is.

But in "store" the batteries are supposed to be disconnected from any use, and you say yours are not but run down as they are not being charged when you have 120 volt power. I am wondering if your use/store switch or relay are not working properly or is wired incorrectly. The converter/charger should not be isolated in "store", the batteries should be though. The idea is that in store, the batteries cannot be discharged (other than the propane detector and inverter as well as the power jack which is direct wired to the battery bank).

At least that is the way mine works. I will look at a PDF of the manual tomorrow to see what that says about the design.
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Old 12-17-2014, 07:34 AM   #13
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We (AM Solar) use a battery disconnect (along with a disconnect for the solar array) in all of our premium installations. These are clearly designated oh the block wiring diagrams on AM Solar's web site.

Airstream wires their solar pre-wire to the DC bus bars and NOT directly to the batteries, as we do. Further, 10 AWG is not sufficient for more that a 100 watt panel if you want to keep your voltage drop below 2% ( as we do).

Every added connection (like bus bars, etc ) rather than direct runs from solar panels to charge controller to batteries will also induce more voltage drop.

Keep it simple and direct for maximum efficiency of your system.


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Old 12-17-2014, 07:57 AM   #14
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Inverter draw in store ...

Quote:
Originally Posted by idroba View Post
I don't have the factory solar package, just the one I self installed. But it is directly connected to the batteries, apparently the same way yours is.

The idea is that in store, the batteries cannot be discharged (other than the propane detector and inverter as well as the power jack which is direct wired to the battery bank).

At least that is the way mine works. I will look at a PDF of the manual tomorrow to see what that says about the design.
-- I get it about the propane detector and power jack.... But, are you saying that if my factory inverter remote switch is in the "off" position, that it is still drawing power from the battery while in "store" mode ?????

Thanks for any insight on that item...
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