Reply
 
Thread Tools Search this Thread Display Modes
 
Old 02-03-2019, 08:47 AM   #1
2 Rivet Member
 
Currently Looking...
Mary Esther , FL
Join Date: Dec 2018
Posts: 32
Can everything, including the AC, be wired to run off the batteries?

We are looking to buy a new (or gently used, if we can find one) FC30FB Bunk for full-time living. One of our desired goals is the ability to boondock in relative comfort (I can tolerate pretty much any temp, but I want to at least have the option of decently-conditioned air for the rest of the family!).

So, specifically, it is my understanding that the Air Conditioners are only connected to the AC side of the trailer's "power grid," and thus cannot be powered by the batteries (if this is incorrect, please school me!). I was wondering if it is instead possible to wire the AC unit to be powered by the DC "grid."

To be clear, I have no expectation of running the Air conditioner (or any high-consumption appliances) purely off the stock or near-stock batteries. The intent would be to simply use the batteries to provide surge power for AC startup and intermittent appliance use.

For example, the 13500 BTU AC should pull about 2700w at startup, but only run on around 1250w. Thus, assuming perhaps a 50% duty cycle at a reasonable setting, we are only looking at maybe 700-800 watt-hours including the startup surges (say, ~2700 watts for 15 seconds every 10 minutes). Thus, a quieter, cheaper, more economic, and much more portable 2000w-class generator should easily be able to provide a net positive charge to the battery throughout the day.

A modest solar setup should make it that much easier to maintain battery charge.

Thoughts on how difficult it would be to set uo the airstream to operate like this?

Thanks!
__________________

Lindenwood is offline   Reply With Quote
Old 02-03-2019, 09:02 AM   #2
Well Preserved
 
overlander63's Avatar

 
1993 21' Sovereign
Colfax , North Carolina
Join Date: Jun 2003
Posts: 20,765
You can wire the air conditioner to run off the batteries, using a 3000watt inverter, but be advised that when inverting 12v to 120v, you need to multiply the watt draw by 10x. You'd be drawing 30000 watts, or about 300 amps, to start the air conditioner. Even the biggest, baddest batteries won't hold up long to that load.
Some people have wired their air conditioner to run for a brief period on their batteries, using an inverter, but basically only for a few minutes to take the heat out of the trailer, then it's back to windows and vents.
You would also need a huge bank of solar panels to have any hope of replenishing the batteries between uses.
Also, if you are planning to do this in Florida, be advised it is a state law that any residence is required to be connected to the power grid.
__________________

__________________
Meddle not in the affairs of dragons, for you are crunchy, and taste good with ketchup.
Terry
overlander63 is offline   Reply With Quote
Old 02-03-2019, 09:05 AM   #3
Rivet Master
 
blkmagikca's Avatar

 
1987 32' Excella
Nepean , Ontario
Join Date: Mar 2006
Posts: 1,279
From a practical point of view, forget about running the air conditioner off your batteries (e.g., using an inverter/charger) - you would need an obscene amount of solar panels and LiFePO batteries. It is highly unlikely that you would have enough "real estate" to mount solar panelling to do this. If you install The Easy Start module - see https://www.microair.net/products/ea...nt=30176048267 - you would be able to run the a/c using a 2000 series inverter type generator, such as the Honda 2000 or Yamaha 2000i.
__________________
VE3JDZ
AIR 12148
1987 Excella 32-foot
1999 Dodge Ram 2500HD Diesel
WBCCI 8080
blkmagikca is offline   Reply With Quote
Old 02-03-2019, 09:10 AM   #4
Rivet Master
Commercial Member
 
lewster's Avatar
 
Vintage Kin Owner
Naples, FL , Hood River, OR
Join Date: Dec 2005
Posts: 7,339
Hi Lindenwood,

It is entirely possible for you to connect your roof A/C (only 1 of your 2 units) to your batteries ( I do this all the time) to allow you to operate the A/C for a specific period of time. The only thing you have to worry about is the power required by your A/C and your battery life.

You will also need a new, larger inverter/charger (minimum of 2000 watts), new, much larger batteries and a solar system that will allow you to re-charge your batteries as they deplete.

Anything is possible, it simply requires the time and money to accomplish and a person who can do the job for you!
__________________
Lew Farber...ABYC Certified Master Marine Electrician...RVIA Certified Master Tech ...AM Solar Authorized Installation Center...AIRSTREAM Solar & Electrical Specialist...Micro Air 'Easy Start' Sales and Installations
lewster is offline   Reply With Quote
Old 02-03-2019, 09:35 AM   #5
Rivet Master
 
Al and Missy's Avatar

 
2002 30' Classic S/O
Melbourne Beach , Florida
Join Date: Nov 2013
Posts: 3,133
Quote:
Originally Posted by overlander63 View Post
You can wire the air conditioner to run off the batteries, using a 3000watt inverter, but be advised that when inverting 12v to 120v, you need to multiply the watt draw by 10x. You'd be drawing 30000 watts, or about 300 amps, to start the air conditioner. Even the biggest, baddest batteries won't hold up long to that load.
Some people have wired their air conditioner to run for a brief period on their batteries, using an inverter, but basically only for a few minutes to take the heat out of the trailer, then it's back to windows and vents.
You would also need a huge bank of solar panels to have any hope of replenishing the batteries between uses.
Also, if you are planning to do this in Florida, be advised it is a state law that any residence is required to be connected to the power grid.
One does not multiply the wattage draw by the voltage ratio, only the current. Neglecting, for the moment, inverter efficiency, the wattage at 12 volts is the same as the wattage at 120 volts, but since the voltage goes down by a factor of 12, the current comes up by the same amount plus a little to account for efficiency of the inverter. So a 30 amp starting current becomes 360 amps and a 15 amp run current becomes 180 amps.

It looks like you did the math right, just mis-stated the reason.

OP: An EasyStart can significantly reduce the starting current, as previously stated, but being realistic, you are going to be running the generator whenever you are running the AC.

Al
__________________

"You cannot reason someone out of a position they have not been reasoned into"

Al, K5TAN and Missy, N4RGO
2002 Classic 30 Slideout
S/OS #004
2013 Dodge 2500 Laramie 4x4 Megacab Cummins
2001 Safari 25 RB Twin (Gone, but not forgotten)
WBCCI 1322, TAC FL-39, AIR 82265

Al and Missy is offline   Reply With Quote
Old 02-03-2019, 09:36 AM   #6
Rivet Master
 
SuperTrouper's Avatar

 
2008 27' International FB
Petaluma , California
Join Date: May 2011
Posts: 667
Images: 5
Quote:
Originally Posted by overlander63 View Post
Snip...but be advised that when inverting 12v to 120v, you need to multiply the watt draw by 10x. You'd be drawing 30000 watts, or about 300 amps, to start the air conditioner. snip
Clarification, the watts don't change.

DC watts to amps calculation formula
The current I in amps (A) is equal to the power P in watts (W), divided by the voltage V in volts (V):

I(A) = P(W) / V(V)

So amps are equal to watts divided by volts.

amp = watt / volt

or

A = W / V

Alternating current calculations are a little more complicated and there are losses in the conversion from DC to AC but the simple calculation is close enough for discussion. So, if the Air Conditioner draws 30 amps at 120 Volts then the power (watts) is 30 x 120 or 3600 Watts. The power required remains the same. If your source becomes 12V then the math says 3600 watts divided by 12 volts is 300 Amps. Given a large battery bank of 300AH (Amp hours) and utilization of only 50% of that (assuming lead acid batteries) you could theoretically run this load for a half hour before the batteries are depleted. In reality, as mentioned in the original post the AC only draws max power at compressor start up and then hums along at 1400 watts or so.

Lewster is the best resource for the discussion here. For us, a MicroAire EasyStart and a Westinghouse 2500 Watt genny is what we have in the case we need AC without hookups but so far, we have not needed the AC here in Northern California our 400 watts of solar and 220AH of batteries have sufficed for our needs. I've only run the generator at home to keep it operational.
SuperTrouper is offline   Reply With Quote
Old 02-03-2019, 09:58 AM   #7
Rivet Master
 
kscherzi's Avatar
 
2013 27' FB International
El Dorado Hills , California
Join Date: Jan 2013
Posts: 1,222
Images: 24
I've noticed my 15,000 BTU AC draws nearly 2,000 watts continuous at 120 volts according my kill-a-watt meter.
kscherzi is offline   Reply With Quote
Old 02-03-2019, 10:17 AM   #8
4 Rivet Member
 
2dabeach's Avatar
 
2007 25' Safari FB SE
North/East , New Jersey
Join Date: Nov 2006
Posts: 315
Lindenwood....Buy yourself a 3,000 watt Honda generator instead of a 2,000 unit and you should not have a problem running a single A/C.
__________________
2007 Safari 25' FBSE LS
2006 GMC Sierra 2500HD Crew Cab 4WD Duramax
2dabeach is offline   Reply With Quote
Old 02-03-2019, 10:42 AM   #9
4 Rivet Member
 
DeltaRon's Avatar
 
2015 28' Flying Cloud
Cumming , Georgia
Join Date: Jul 2014
Posts: 339
AC on batteries

And Lewster is the guy that help you convert. There’s no better power, solar guy in the country. And he works out of Naples during the winter months. Call him.
DeltaRon is offline   Reply With Quote
Old 02-03-2019, 10:49 AM   #10
Rivet Master
 
switz's Avatar

 
2014 31' Classic
2015 23' International
2013 25' FB International
Apache Junction , Arizona
Join Date: Sep 2012
Posts: 5,286
Images: 8
We installed nine 100 watt solar panels on the roof go our 2014 Classic along with a 600 amp hour lithium battery and Magnum MS2812 charger/inverter plus all the solar controls. All of the trailer AC wiring connects through the Magnum except the original refrigerator (now a Vertifrigo 12Vdc only), the original water heater (now a Truma Aqua Do comfort instant on propane only) and one of the two air conditioners.

Thus all 120Vac outlets and one air conditioner can run off of the battery, However, the air conditioner will suck a lot of amp hours. We have run the air conditioner for a 30 minute lunch stop with no issues.
__________________
WBCCI Life Member 5123, AIR 70341, 4CU, WD9EMC

TV - 2012 Dodge 2500 4x4 Cummins HO, automatic, Centramatics, Kelderman level ride airbag suspension, bed shell

2014 31' Classic model 30 twin beds, 50 amp service, 900 watt solar system, Centramatics, Dill TPMS, disc brakes, 16" tires & wheels
switz is offline   Reply With Quote
Old 02-03-2019, 10:53 AM   #11
2 Rivet Member
 
mykytiukr's Avatar
 
1965 24' Tradewind
almena , Wisconsin
Join Date: Jul 2014
Posts: 85
Boondocking!

Do a search on YouTube for “Solar RV Airconditioning”. There are many many videos of people doing exactly what you are asking about. There is one where a guy is using a small window AC that starts with about 1000 watts and runs a about 500.
mykytiukr is offline   Reply With Quote
Old 02-03-2019, 11:00 AM   #12
2 Rivet Member
 
2016 27' Flying Cloud
Newport Beach , California
Join Date: Jul 2016
Posts: 20
My friend Rob Thilo has a 2016 Classic with the set up you want and it’s for sale. Talk with him
rchawkins is offline   Reply With Quote
Old 02-03-2019, 11:01 AM   #13
2 Rivet Member
 
mykytiukr's Avatar
 
1965 24' Tradewind
almena , Wisconsin
Join Date: Jul 2014
Posts: 85
https://www.amazon.com/Frigidaire-FF.../dp/B01B4XUUDI Here is the link to the small AC unit he used.
mykytiukr is offline   Reply With Quote
Old 02-03-2019, 11:14 AM   #14
Rivet Master
 
TheGreatleys's Avatar

 
1974 27' Overlander
Baltimore , Maryland
Join Date: Mar 2016
Posts: 867
Quote:
Originally Posted by Lindenwood View Post
We are looking to buy a new (or gently used, if we can find one) FC30FB Bunk for full-time living. One of our desired goals is the ability to boondock in relative comfort (I can tolerate pretty much any temp, but I want to at least have the option of decently-conditioned air for the rest of the family!).

So, specifically, it is my understanding that the Air Conditioners are only connected to the AC side of the trailer's "power grid," and thus cannot be powered by the batteries (if this is incorrect, please school me!). I was wondering if it is instead possible to wire the AC unit to be powered by the DC "grid."

To be clear, I have no expectation of running the Air conditioner (or any high-consumption appliances) purely off the stock or near-stock batteries. The intent would be to simply use the batteries to provide surge power for AC startup and intermittent appliance use.

For example, the 13500 BTU AC should pull about 2700w at startup, but only run on around 1250w. Thus, assuming perhaps a 50% duty cycle at a reasonable setting, we are only looking at maybe 700-800 watt-hours including the startup surges (say, ~2700 watts for 15 seconds every 10 minutes). Thus, a quieter, cheaper, more economic, and much more portable 2000w-class generator should easily be able to provide a net positive charge to the battery throughout the day.

A modest solar setup should make it that much easier to maintain battery charge.

Thoughts on how difficult it would be to set uo the airstream to operate like this?

Thanks!
My rig is wired like that. My relatively large inverter with "pass-through" functionality is wired in-line with my shore power, prior to the breaker box. Turn the inverter on, and it powers everything in the trailer from the batteries. It won't run the AC for very long on batteries before they die, but it will start and run it.

If you want to supplement a low output generator with your batteries, you'll want a "hybrid" inverter, which is designed to do just that. My inverter is not a "hybrid" type, so I can choose to power with either shore power or batteries, but not both at the same time.

All that said, if your goal is just to run your AC with a Honda 2000 generator or something similar, it would be cheaper and easier just to install an Easy Start on your AC unit to lower the startup surge to a level that the generator could handle. Unless you have a very large solar array and/or battery bank, it's not all that helpful to be able to run the AC off batteries.
__________________

TheGreatleys is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Termites ate everything. Including the floor. I refuse a shell off! CraigFulton Repairing/Replacing Floor &/or Frame 102 10-30-2016 04:57 PM
Can't remember how the batteries were wired! stephenb Batteries, Univolts, Converters & Inverters 5 04-06-2016 02:16 PM
I'm importing one to Australia and blogging about it including costs mattmorphett Shipping & Export/Import 20 02-26-2014 06:06 PM
anyone have pics of a custom stereo install? including subwoofer in old stream streamahead Audio, Video & TV 10 10-13-2010 10:35 PM
Cost for a new 454 motor including installation? bugsbunny Airstream Motorhome Forums 6 11-11-2003 08:13 AM


Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by the Airstream, Inc. or any of its affiliates. Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 04:49 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.