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Old 02-18-2014, 02:51 PM   #1
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Battery Switch Inside "On" or "Off"?

Ok, I have read the manual front to back, and am still confused. Our rig is a 2014 Sport 22FB. By the front bed is the battery disconnect switch. When the trailer is in storage, I turn that switch "off" to prevent any phantom drains. When we take the Airstream out, I turn the switch "on", and leave it on for the duration of the trip. We are not boondocking, but are connected to shore power while camping. Two questions:

1) Can the battery be overcharged by being connected to shore power with the battery switch in the "on " position for several days? What if I am connected to shore power, and leave the 7 pin plugged into the TV?

2) Under what circumstances, if any, would I want/need to turn the battery switch "off" while connected to shore power?

Thanks in advance.
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Old 02-18-2014, 03:38 PM   #2
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With the converter that Airstream supplies, you'll eventually overcharge the battery if you leave it on shore power all the time. If it's just on shore power when you're actually traveling and camping in it, that'll take a long time but it will likely shorten the life of your battery somewhat.

Whether the converter backfeeds your TV through the umbilical depends on your TV. Some have a diode that prevents it, some disconnect the charge line when the ignition is switched off, some would allow it. You're not likely to get enough current feeding back to harm your TV's battery even over weeks of having it plugged in, and any way the only time you're likely to be both on shore power and plugged into the TV is on an overnight stop where you don't unhitch.

I can't remember if the new ones isolate the battery from being charged in "store." I think they do, and in any event it would be easy to check. The tricky thing about the store/use solenoid is that the light is always on when you're plugged in, so you need to unplug to be 100% sure of the state of the solenoid. Unplug, switch to "store", check the battery voltage (at the battery posts directly), plug in, recheck the voltage. If it's the same (12.7-ish volts) then they're isolated when in Store, if the voltage jumps up then they're being charged in Store.

So, if they're isolated, you could switch to Store after a few days at a campsite when you're sure the batteries are fully charged. I think the propane detector is wired right to the batteries, so it'll eventually drain them and you'll need to charge again.

Someone with a trailer new enough to have that store/use switch will be along presently to give a more definitive answer. If I want to disconnect my battery I have to open the battery box, old-school like.
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Old 02-18-2014, 03:53 PM   #3
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You are correct to switch to "store" while your rig is in storage and disconnected from shore power, for exactly the reasons you describe ... to isolate the battery from phantom draws. For long, extended times of storage some folks physically disconnect the batteries and put them on a battery minder to maintain them over the long haul, but for intermittent periods of storage you should be fine.

Likewise, you are correct in switching to "use" while camping in your rig...even if you are plugged into shore power. (In fact, if I am not mistaken, being plugged in overrides the disconnect ... at last that is the case with ours.) It is highly unlikely that your batteries will be overcharged when plugged in while you are camping in it because there are draws on the battery all the whole time ... lights, frig, propane detector, furnace, etc.

We store our rig at home, plugged into 30-amp continuously. We do not switch to "store" during that time, however we leave the frig on, use the lights, water pump, furnace, AC, TV and radio from time to time — we pretty much doing everything one would do while camping, but sleeping in it — so in our case, there are constant draws during our version of "storage" ... so far our batteries have, therefore, never overcharge.

We typically disconnect from the tow vehicle when we stop, even if we are just there for the night ... just to make sure.
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Old 02-18-2014, 06:30 PM   #4
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On my 2014 FC 20' when in the store mode, the battery is disconnected from the loads in the trailer except:

1.The propane detector which is always on and takes 6 to 8 mA constantly. It is not shut down by the Store/Use switch.
2.The optional inverter which is wired directly to the batteries and does not go through the Store disconnect. So, you could turn the inverter on by accident and run the batteries down even in the Store mode. My inverter has a large standby current of 1.75 amps, when doing nothing at all so that discharge is a potential for killing the batteries easily.

When in Store mode the converter/charger is disconnected from the batteries but will supply 12 volts for the lights and other 12 volt items in the rig. But it will not charge the batteries, or allow them to be discharged, other than the two items mentioned above.

I have a modern 3 stage converter/charger in my rig now, not the original Paralax which came with it from the factory. So, I have no problems leaving my Store switch on all the time. With the original Paralax I would probably limit the time that the rig was plugged in and the store switch on to maybe a week if the unit is unused. That would minimize the possibility of a battery overcharge situation. But it is not something you need to be paranoid about. Just don't leave the rig plugged in for months with the original Paralax converter/charger.

In looking at the 12 volt electrical diagram, it appears that the Tow Vehicle charge line is directly connected to the Airstream batteries and is not disconnected by the Store mode switch. So, if the Tow Vehicle is left plugged into the Airstream and does not have a relay in the tow vehicle itself, it will be charged by the converter/charger if the Store mode switch is left in the Use position, but not if it is in the Store position, same as the Airstream batteries. Some tow vehicles have an isolation relay, some do not. My 2012 Jeep Grand Cherokee does not. I believe Ford's do. No idea about GM vehicles.

The Use/Store switch is a relatively complicated thing to wrap your mind around, so don't stress if you don't understand it at first. It may take a while, I know it did with me and I am pretty electrically savy.
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Old 02-18-2014, 09:31 PM   #5
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When stored we select "STORE" to isolate everything but the propane detector from the batteries.

When plugged into shore power we select "STORE" to isolate the batteries from being repeatedly overcharged and ruined by the Parallax converter.

We have a solar system to keep the batteries up.

The only time we select the "USE" position is when towing to keep the refrigerator running on propane, and when dry camping to power the 12 volt equipment.
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Old 02-19-2014, 03:51 AM   #6
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Quote:
Originally Posted by dkottum View Post

When plugged into shore power we select "STORE" to isolate the batteries from being repeatedly overcharged and ruined by the Parallax converter.

.
Why doesn't your trailers electronics automatically charge your batteries?
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Old 02-19-2014, 05:38 AM   #7
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Quote:
Originally Posted by r carl View Post
Why doesn't your trailers electronics automatically charge your batteries?
They do, but Airstream uses cheap single stage chargers and they overcharge the batteries.

We've replaced ours with a three stage charger, and now I never turn the switch to store.
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Old 02-19-2014, 06:11 AM   #8
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They do, but Airstream uses cheap single stage chargers and they overcharge the batteries.

We've replaced ours with a three stage charger, and now I never turn the switch to store.
Don't the single stage chargers have voltage regulators? My 1985 Avion with original electrics doesn't overcharge my batteries.
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Old 02-20-2014, 07:50 AM   #9
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There are many accounts of the stock Airstream converter overcharging and ruining batteries, other than that it works fine. (It ruined the batteries in two years on our 2007 Airstream before we bought this new trailer with the solar system.)

So by using the "STORE" battery position whenever plugged into external power, we never allow the converter to charge our batteries. Only the solar system does, or the truck when towing.
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