AC inverter with deep cycle battery........

bob1961
bob1961 Registered Users Posts: 9 ✭
in Off Grid Solar & Battery Systems #1
i'm looking for spec's on size of marine deep cycle battery to use with an AC inverter, that I can power my freezer and fridge with where i'm renting when I lose power....right now I have 64 oz plastic bottles full of water and frozen, but with 15 but they take up space....here is the inverter i'm looking at....

http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_12-volt-1100-watt-continuous-2200-watt-peak-modified-sine-wave-power-inverter-powerbright_10271229-p?searchTerm=ac+inverters

i'm not sure if this will be good enough to run off one batt to power the freezer and fridge....also what kind of hours or how can I find out how long it will power those two from the battery....only long time we had no power was for 29 hours when sandy came throught and took trees down, thx....
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: AC inverter with deep cycle battery........

    Don't do it.
    Marine/RV type "deep cycle" batteries are just automotive batteries with thick plates.
    That inverter is a MSW (square wave) inverter which the 'frige motor may not like. Even though it is rated as 2200 Watts surge it is questionable whether it would start the refrigerator.

    Run your 'frige through a Kill-A-Watt and get a good idea how much power it draws and uses. You will not be able to see the start-up surge, however. When you have these numbers you can get a good idea how much battery power you will need.

    Typically a refrigerator will use about 1.2 kW hours AC. This can be supplied by a pair of 6 Volt 220 Amp hour "golf cart" real deep cycle batteries in series. You would also need a good inverter, like a Xantrex Prosine 1800 or 2000. And you will need good wiring between the two.

    If you try to do it "on the cheap" it may work, or it may fail when you need it most. There's nothing worse than thinking you've got emergency power and then finding out when power goes down that you don't.

    All things considered, generators are a much better value for back-up power.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: AC inverter with deep cycle battery........

    Just to add to Marc's comments... A pair of 6 volt @ 220 AH golf cart batteries running a 1.2kWH per day freezer:

    2 batteries * 6 volts * 220 AH * 0.85 AC inverter eff * 1/1,200 WH per day = 1.87 days of power to batteries "dead"

    So, about 2 days of energy storage to battery bank "dead" (meaning a new battery bank needed). Or, if you discharge to 50% battery state of charge (longer battery life), you will get almost 24 hours of backup cooling.

    Any freezer that is not opened often should last 24 hours before defrosting... So not much help.

    A Honda eu2000i genset (50 lb suitcase model) will supply around 400 watts for 9+ hours on 1 gallon of gasoline. ~$1,000 for genset delivered to your front door.

    Run the Honda for 6 hours in evening and 3 hours in the morning, run a fridge+freezer+lights+laptop computer+cell phone charger+etc. on ~1 gallon of fuel per day.

    Got a car that you can siphon for 5 gallons of fuel--5 days of (portable) backup power (along with a couple quarts of oil).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    #4
    Re: AC inverter with deep cycle battery........

    If you go the battery and inverter route, I would research and be sure your inverter has good surge capability. I was previously using a Xantrex Prowatt 2000 and I had serious issues with starting devices with a large surge, such as a large TV set or a fridge, when the batteries were at less than full charge. In contrast, a good inverter such as the Outback VFX 3524 exhibits none of these surge starting issues, with equivalent battery bank size and cabling. And my fridge was a relative efficient one, with just over 500 watt hours usage per day, and typically drawing just over 100 watts when in normal operation. The occasional defrost cycle would kick in at about 1000 watts.

    Best to go with a generator as coot mentioned, if your just looking for emergency backup for a power outage.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: AC inverter with deep cycle battery........

    There's quite a difference between a 12 Volt 2kW inverter and a 24 Volt 3.5 kW inverter. Not the least of which is the price. ;)
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #6
    Re: AC inverter with deep cycle battery........

    Yeah, something like $1,800 or so.

    PowerBright 12 Volt 1100 Watt Continuous/2200 Watt Peak Modified Sine Wave Power Inverter
    Part No. PW1100-12 $99.99
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  • bob1961
    bob1961 Registered Users Posts: 9 ✭
    #7
    Re: AC inverter with deep cycle battery........

    hey thx guys, i'm just trying to have power when I need it....right now cost of a portable gen is out of reach money wise, unless I can fine one for bout 250.00....
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #8
    Re: AC inverter with deep cycle battery........
    bob1961 wrote: »
    hey thx guys, i'm just trying to have power when I need it....right now cost of a portable gen is out of reach money wise, unless I can fine one for bout 250.00....
    Bob, That Inverter will probably pull your Refrigerator just fine, but I doubt both. You'll need good cables to hook it up to the Batteries. I would not skimp here some, 2/0 welding type cable and a fuse, keep the cables short, say 3 ft, you'll also need a interconnect cable to run the batteries in series, the cables will cost almost as the Inverter. If you go with 2 , 6v Golf Cart batteries they will be about $ 90 each. This size cables will keep the voltage sag to a minimum, if the voltage sags the Inverter will cut out due to low voltage.

    The problem is you can't keep it working long without a way to re-charge the batteries.
    .
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  • bob1961
    bob1961 Registered Users Posts: 9 ✭
    #9
    Re: AC inverter with deep cycle battery........

    I have welder cable from an old Hobart welder that is a good guage size, yeah I have space to keep the inverter and batt's close to each other....I used to work as an auto tech and know the routine on wiring batteries together both ways....just turning my MacGyver mind to keep my food cold when I lose power, well time to keep thinking, lol....
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #10
    Re: AC inverter with deep cycle battery........
    bob1961 wrote: »
    I have welder cable from an old Hobart welder that is a good guage size, yeah I have space to keep the inverter and batt's close to each other....I used to work as an auto tech and know the routine on wiring batteries together both ways....just turning my MacGyver mind to keep my food cold when I lose power, well time to keep thinking, lol....
    You sound like you know how things work. It's not the running power that gets you in this case , it's the Starting load. I just doubt that you could have one running and be able to start the other, but you could try and see if it kicks the Inverter out. That doesn't mean that you couldn't run one for a couple hrs and then switch. I think Coot brought up that the freezer wouldn't have to run as much as the refrigerator. In a pinch you could do some charging with a car or truck alternator, that usually does not give you much in charging amps. You could rig up a alternator to a lawn mower engine, you wouldn't be the first.
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  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    #11
    Re: AC inverter with deep cycle battery........
    Blackcherry04 wrote: »
    It's not the running power that gets you in this case , it's the Starting load.

    That is a major issue with an inverter without really good surge handling. I can not count the number of times I've had my smaller inverter (Xantrex Prowatt 2000) kick out, due to starting a high surge load. Once the batteries are down a bit, this will most likely be an issue unless you have a good inverter.
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  • bob1961
    bob1961 Registered Users Posts: 9 ✭
    #12
    Re: AC inverter with deep cycle battery........

    I do have an AC/DC charger that I use for my R/C hobby that can charge a 6/12 v batteries off my trucks battery if I need to....I did a search for portable gens and my wallet bit me in my butt, LOL....when we do lose power it's a rush to get frozen food from our main fridge freezer to the upright freezer, then we don't open it unless we have to....food from the fridge goes into the fridges freezer so it stays colder then not opening the reg fridge, we have it worked out to a science, lol....
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