Reply
 
Thread Tools Display Modes
 
Old 07-20-2012, 12:06 AM   #1
Platinum Member
 
markopolo's Avatar
 
Join Date: Oct 2006
Location: New Brunswick, Canada
Posts: 7,800
Default Running small Air Conditioner on an inverter

EDIT: I split the posts below from the Rear Window Air Conditioner topic: http://www.classbforum.com/phpBB2/vi...hp?f=12&t=2156
I think it will be easier to follow both topics now
__________________________________________________ __________________________________________________ ____________

I don't have a generator in my van so a smaller air conditioner appealed to me because I can run it off an inverter for a short time.
I have a 1,000 watt pure sine wave inverter wired into the vans electrical system with an automatic transfer switch. My 2 AGM house batteries total 180ah capacity.

Fedders air conditioner specs:
BTU Cooling: 5200
Voltage: 115
Amps Cooling: 4.5
Watts Cooling: 485
Plug Cap. Amps: 10
Weight: 38.6 lbs

I tested this setup today:

With the van engine running and the rear window air conditioner running off my inverter the voltage at my house batteries was 13.9 volts with all battery banks combined with a manual battery selector switch. The voltage was 13.7v using only the isolator to combine the banks. To me that means my alternator at idle supplies the current needed to run the air conditioner.

The inverter showed the output watts at 420w. That varied a bit from 370 to 410 to 390 etc.
With the motor off and running off my inverter only on my house batteries the DC amp draw got as high as 35.5ah. It varied from 31.5 to 35.5.
AC amps usually showed 3.95ah. It varied a bit from 3.68 to 3.95.

In the rear of the van (setup like a RT 190 Versatile) the starting temperature of 85F dropped to 79 in 5 minutes. At 10 minutes the temperature was 74.5F and at 15 minutes it was 71.6F. I turned of the A/C at 15 minutes. The 88F front cab temperature didn't drop much during the 15 minute test although it had continued to drop when I checked at the 20 minute mark (a/c had been off for 5 minutes by then). I was parked in direct sun.

The air conditioner compressor will cycle on and off as needed depending on the temperature. If I set the temperature on the A/C at 72F I could get up to two hours compressor cooling time which might equal 3 to 4 hours of a cool rear section of the van if I further block off that rear area. That might make the difference of a good nights sleep or not. This will really only be practical if I'll be driving for a few hours the next day or will soon have access to grid power to recharge the battery bank.

Please post any comments or advice.

2nd Edit: The van was parked in full mid-day summer sun and I have 120 watts (or maybe more) of solar panels on the roof. The input from the solar panels would have affected the test results above.
__________________

__________________
Two bikes on sliding cargo box: https://www.classbforum.com/forums/m...icture206.html & 1997 GMC Savana 6.5L Turbo Diesel Custom Camper Van Specifications: https://www.classbforum.com/forums/f...vana-5864.html
markopolo is offline   Reply With Quote
Old 08-06-2012, 05:33 PM   #2
New Member
 
Join Date: Aug 2012
Posts: 8
Default Re: Rear Window Air Conditioner

Hello Marko,
I have become a member about 5 minutes ago.
I wanted to ask you about starting the window AC on batteries.
I have tried to do what you did 2 months ago, but it did not work.
As soon as i turned the AC on (5000 btu), the inverter started bipping and the red light came on and it just wouldn't start the little ac.
A friend told me that this is because the voltage from the batteries dropped down rapidly trying to provide the electrical load the ac needed, and the inverter's protection kicked in because of that.
Could you please give me an advice on that issue?
Thanks
__________________

pjc188 is offline   Reply With Quote
Old 08-06-2012, 10:28 PM   #3
Platinum Member
 
markopolo's Avatar
 
Join Date: Oct 2006
Location: New Brunswick, Canada
Posts: 7,800
Default Re: Rear Window Air Conditioner

On batteries only: (van motor not running) The same thing will happen with my system if I try to start it in "Cool" mode. My inverter will beep and shut-off.
If I start the A/C unit in "Fan" mode and let it run a minute or two and then select "Cool" it works.

The thing for me to remember is to put the A/C in "Fan" mode before I turn it off. It will remember that setting on the next start-up.

That 15 minute test I ran was actually on batteries only. I know my report wasn't clear on that. My results could have been influenced a bit by some voltage input input from the solar panels on my roof because I was parked in full sun.

Today, with the van parked in my garage, and no input from the solar panels, I could not measure the DC amp draw because it exceeded my clamp on ammeter 40 amp limit. On the original 15 minute test the amp draw didn't exceed 35.5 amps DC. I only thought of the solar panel affect today.

My inverter is a bit small for the startup load. It is rated 1000 watt continuous /1100 watt five minutes /2000 watt surge. It is a Pure Sine Wave type.
I have two AGM house batteries. All test were done with fully charged batteries.

Some sort of "hard start" capacitor installed in the A/C might help. Particularly, when the batteries are not at full capacity.

Anyone know if a car amp audio 12v capacitor would help with the start-up loads when using an inverter?
Or would a 110V capacitor like the Supco SPP6E be more effective? http://www.supco.com/eclass.htm
__________________
Two bikes on sliding cargo box: https://www.classbforum.com/forums/m...icture206.html & 1997 GMC Savana 6.5L Turbo Diesel Custom Camper Van Specifications: https://www.classbforum.com/forums/f...vana-5864.html
markopolo is offline   Reply With Quote
Old 08-07-2012, 04:49 AM   #4
New Member
 
Join Date: Aug 2012
Posts: 8
Default Re: Rear Window Air Conditioner

Thank you for your reply.
You mentioned your inverter is a little bit small for that startup load.
Do you think if i use 2000 running 4000 surge it will not have any problems starting the compressor?My AC is 4.5 amp running - couldn't find the start amps, even after trying ro contact manufacturer.
pjc188 is offline   Reply With Quote
Old 08-07-2012, 12:45 PM   #5
Platinum Member
 
markopolo's Avatar
 
Join Date: Oct 2006
Location: New Brunswick, Canada
Posts: 7,800
Default Re: Rear Window Air Conditioner

For me, running the air conditioner on the inverter is a "no-other-choice" option. I wouldn't want to spend too much money on the project because you are always going to be limited by the size and condition of your battery bank and also recharging that battery bank. A small and quiet Honda or Yamaha generator could run the air conditioner all day and night as long as you have gas to put in the tank.

Back to your question Yes, a 2000 watt inverter would have a better chance.

I read (on a few websites) that startup loads can be 3 to 7 times the rated running watts. But, for small air conditioners like mine, my guess is that the surge can't be much more than the 15 amp AC rating of a typical household circuit. My air conditioner specs show only a 10amp ac plug rating. So the surge from my air conditioner might only be around 1200 to 1800 watts or so. I think it is the duration of the surge and not just the load that causes my inverter shutdown. Mine displays: OLP - which is AC output Over load shutdown. So, an inverter with a 2000 watt continuous rating should handle that startup much better.

What size inverter are you using?
How many batteries?
What gauge wire are you using to connect the inverter to the battery bank?
What is the length of those wires?
Does your air conditioner start-up if you turn on the fan first, then wait bit, and then start cooling?
__________________
Two bikes on sliding cargo box: https://www.classbforum.com/forums/m...icture206.html & 1997 GMC Savana 6.5L Turbo Diesel Custom Camper Van Specifications: https://www.classbforum.com/forums/f...vana-5864.html
markopolo is offline   Reply With Quote
Old 08-07-2012, 01:38 PM   #6
Platinum Member
 
markopolo's Avatar
 
Join Date: Oct 2006
Location: New Brunswick, Canada
Posts: 7,800
Default Re: Rear Window Air Conditioner

Update - my 1200 to 1800 watts surge guess looks to be way too low based on this guy's testing:

http://www.wind-sun.com/ForumVB/show...377#post122377 and
http://www.wind-sun.com/ForumVB/show...917#post122917

[youtube:1w9p0gqr]SxV7rv5wTUg[/youtube:1w9p0gqr]

22.6 amps AC inrush current on the 5000 btu Goldstar a/c he tested. Maybe 2500 to 2700 watt surge.
__________________
Two bikes on sliding cargo box: https://www.classbforum.com/forums/m...icture206.html & 1997 GMC Savana 6.5L Turbo Diesel Custom Camper Van Specifications: https://www.classbforum.com/forums/f...vana-5864.html
markopolo is offline   Reply With Quote
Old 08-07-2012, 05:30 PM   #7
Platinum Member
 
markopolo's Avatar
 
Join Date: Oct 2006
Location: New Brunswick, Canada
Posts: 7,800
Default Re: Rear Window Air Conditioner

Quote:
Originally Posted by markopolo
........... I could not measure the DC amp draw because it exceeded my clamp on ammeter 40 amp limit. .........
It can measure up to 400A DC - I just needed to read the selector switch properly



43.5 amp hr draw today on battery only...........

Inverter shows 450 watts AC, voltage dips to 12 volts (from 12.7 volts)

[youtube:2kp5ov5i]HamfusD6gRo[/youtube:2kp5ov5i]
Attached Images
File Type: jpg amps out.jpg (197.0 KB, 4130 views)
__________________
Two bikes on sliding cargo box: https://www.classbforum.com/forums/m...icture206.html & 1997 GMC Savana 6.5L Turbo Diesel Custom Camper Van Specifications: https://www.classbforum.com/forums/f...vana-5864.html
markopolo is offline   Reply With Quote
Old 08-08-2012, 06:37 AM   #8
New Member
 
Join Date: Aug 2012
Posts: 8
Default Re: Rear Window Air Conditioner

Hi Marko,
You mentioned the voltage drop to 12v when running the 5k btu ac.
Isn't this drop close to the inverter's point of low voltage shut off?
Please give more details about voltage drop, amount of batteries (or amp/hour and voltage drop)
Also, what's the minimal safe voltage to operate the batteries?
Thanks again
pjc188 is offline   Reply With Quote
Old 08-08-2012, 11:32 AM   #9
Platinum Member
 
markopolo's Avatar
 
Join Date: Oct 2006
Location: New Brunswick, Canada
Posts: 7,800
Default Re: Rear Window Air Conditioner

The voltage dipping to 12v during a 43 ah load is to be expected. It will drop even more as the battery capacity decreases. It was a very short test and the voltage bounced back to 12.7v as soon as the load was removed.
On my inverter there is a low voltage alarm at 11 volts and low voltage shutdown will occur at 10.5 volts. Those are not resting voltages. They are when the inverter is in use. My inverter needs to see 11.6 volts to restart after a shutdown.

The number of batteries matters. 43 ah from 1 battery is harder on it than two batteries each supplying 21.5 ah. 3 batteries each supplying 14.33 ah is even better etc.

The resting voltages in the red and yellow areas on the following chart are what you want to really avoid. Your batteries will last longer if you don't go below 50% (resting voltage) and always make sure to recharged them as soon as you can.



if you get a chance to answer these questions it might help:
Quote:
What size inverter are you using?
How many batteries?
What gauge wire are you using to connect the inverter to the battery bank?
What is the length of those wires?
Does your air conditioner start-up if you turn on the fan first, then wait bit, and then start cooling?
Attached Images
File Type: jpg state of charge.JPG (47.2 KB, 4309 views)
__________________
Two bikes on sliding cargo box: https://www.classbforum.com/forums/m...icture206.html & 1997 GMC Savana 6.5L Turbo Diesel Custom Camper Van Specifications: https://www.classbforum.com/forums/f...vana-5864.html
markopolo is offline   Reply With Quote
Old 08-08-2012, 04:25 PM   #10
New Member
 
Join Date: Aug 2012
Posts: 8
Default Re: Rear Window Air Conditioner

Thanks again,
So if i understood, you want to avoid less that 50% discharge of your batteries.
But, as soon as you tested the voltage of a full battery, the voltage (under load) got to 12v immediately, which according to the chart you have posted, is very close to the "yellow area" which has the low voltage you wanted to avoid - so is it means that you have a very short time of use of the battery, before getting to the yellow zone, or before the inverter will shut off?

My inverter is 2000/4000 peak
I have 2x6v in series - total 210 amp/h in 12v
6 gauge cables
2 feet long
AC will start cooling immediately - if you switch from fan to cooling, it will turn off the fan completely and then start the compressor and the fan together
__________________

pjc188 is offline   Reply With Quote
Reply

Thread Tools
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


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT. The time now is 12:38 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.