Vacation Bound
Roanoke, Va
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The electric was turned off in the campground where we are staying for about 6.5 hours. The campground did give us advance notice. The only thing we had on the inverter is our Residential refrigerator. Our DirecTV box came on to record a program since we didn't unplug that. We have 4 large batteries and a 2000w inverter. The inverter only stayed on for 4 hours and the battery went to red. Is this normal? We are not mechanically inclined so any advice would be appreciated in basic terms. We did buy a book to try & understand this, but still don't.
Thanks for any advice.
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mena661
Southern California
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Battery went to red? You mean the battery monitor that comes with the RV or something else? That said, depending on how large the load is that you are running from your inverter, your batteries will drop down to a lower voltage while that load is "running". The longer you run the load, the lower the voltage gets. When you remove the load, the battery voltage will come up (not to the level you had before the load though).
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Vacation Bound
Roanoke, Va
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Yes, the battery monitor in the RV. The refrigerator also turned off at that same time.
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mena661
Southern California
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Vacation Bound wrote:Yes, the battery monitor in the RV. The refrigerator also turned off at that same time. Ok, then you basically ran the batteries down below the inverters cut off voltage which caused the inverter to shut off. Being on shore power for only 6.5 hours even with the fridge and TV's running should not run your batteries down that fast. What type of batteries do you have? Also, do you have a voltmeter?
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Vacation Bound
Roanoke, Va
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Our manual says we have a 12-VDC electrical power system consisting of four 6-VDC batteries wired in a series-parallel combination to provide a final 12VDC system providing up to 450 Ampere hours of service. We don't have a voltmeter.
Hope this make sense to someone, it doesn't to us.
Thanks
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vermilye
Oswego, NY, USA
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I'd be concerned about the condition of the batteries.
If the batteries were charged prior to the outage, check that the electrolyte is above the plates and none of the batteries are dry from overcharging.
450 amp hrs of relatively new batteries should have been able to run the refrigerator for more than 4 hours. You should be able to get at least 1/2 the amp hours (225 amp hrs) from the battery bank before the voltage dropped low enough to shut down the inverter. A typical refrigerator would draw around 3-4 amps @ 120V, or 35-45 amps at the 12v batteries (this is figuring about 10% loss from the inverter). If it runs half the time (unless it is very warm out it is probably even less), at the high end that is 45 amps X 2 hrs or 90 amp hours, quite a bit less than 225.
Although it is too late now, for the future if you have or can borrow a kill-o-watt meter, measure the amps the refrigerator draws when running and use that as a starting point for the next time. Unless it is an awfully inefficient refrigerator, it doesn't sound right.
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mena661
Southern California
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450 amp hours is your battery capacity. Typically, you only want to draw them down no further than 50% for long battery life. That's a decent amount of capacity but you could still draw them down too far if not careful. What else were you running during that 6.5 hour period?
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RoyB
King George, VA
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According to an on-line Battery use calculator for a 12VDC Battery with a 450AH rating running a typical 785 WATT fridge load will only last 2.86 hours.
This is obviously using the fridge in the 120VAC mode and not on GAS.
This on-line calculator is pretty close to my actual experience for my 300AH Battery capacity running at 12VDC using a 200W Inverter load for the home entertainment center items when I camp off the power grid which gives me 7.5hours of use time. Use time here is when the battery bank drops to around 12.0VDC or about 50% capacity.
I am just passing on a battery use calculator result. Please don't kill the messanger.
BATTERY USE CALCULATOR
* This post was
edited 12/21/11 03:28pm by RoyB *
My Posts are IMHO based on my experiences - PM me
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2oldman
Wilson Creek WA
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Vacation Bound wrote:Hope this make sense to someone, it doesn't to us. I think some education may be in order. If you don't understand the basics of batteries and inverters you will have a hard time relating to any of the information you've just been given.
This is an excellent starting point... 12v side of life.
Battery FAQ
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Wayne Dohnal
Bend, OR.
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RoyB wrote:According to a Battery use calculators on-line for a 12VDC Battery with a 450AH rating running a typical 785 WATT fridge load will only last 2.86 hours.........Please don't kill the messanger.
Darn, you had to say that! I'll have to go after the calculator instead.
1. It did the math wrong. The answer should be 3.4 hours.
2. A typical RV 6 cu. ft. fridge draws 300 to 350 watts. Double the time to 6.8 hours.
3. The fridge typically runs about a 50% duty cycle, double the time again to 13.6 hours for the final time estimate.
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