djmiranda1
Downey, CA
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I am thinking of adding a small fridge in my enclosed trailer. I dont want to do the whole LP system so I was thinking of running a small 1.7CU. FT. fridge on two 6 Volt batteries. It says it uses 1.1-2 amps. Approx. how long would that run on two batteries before needing to recharge? I currently have a 45amp charger. and my batteries are rated at 225amp hour each.
Thanks,
-David
* This post was
edited 01/24/09 12:06am by djmiranda1 *
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Dirtclods
Newport Beach
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djmiranda1 wrote:I am thinking of adding a small fridge in my enclosed trailer. I dont want to do the whole LP system so I was thinking of running a small 1.7CU. FT. fridge on two 6 Volt batteries. It says it uses 1.1-2 amps. Approx. how long would that run on two batteries before needing to recharge. I currently have a 45amp charger. and my batteries are rated at 225amp hour each.
Thanks,
-David This might help
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hopefulbob
Wichita, KS USA
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Your two 6 volt batteries, rated at 225 ah each, can deliver a total of 225 ah of energy at 12 vols when connected in series. (not 450 ah)
Batteries shouldn't be discharged more than about 50% if you expect them to last. This gives you about 112 ah of energy available at 12 volts before recharging.
Fridge draws 1.5 amps at 120 volts AC. That's 180 watts. Typical inverters are only 80/90% efficient. At 85% efficiency, this means you must put 212 watts (180/.85) into the 12 volt supply side of an inverter, in order to get 180 watts AC output for the fridge.
212 watts/12 vdc input equals 17.6 amps DC at the inverter input. A typical inverter, therefore, will draw approx. 17.6 amps from your batteries whenever the fridge is running.
112 ah available/17.6 amp draw means that your batteries will theoretically last 6.3 hours before you need to recharge. (That's with the fridge running 100% of the time. Not likely. At 50% duty cycle, batteries would last 12.6 hours, etc.)
Be aware that compressor-type fridges have high starting current. You will need at least a 600 watt inverter to start your fridge. 600 watt inverter may not be big enough. (depends on the specific inverter)
Above ignores the effect of the high battery discharge rate. Your batteries are rated to deliver 225 ah when discharged over a 20 hour time period. They will not deliver 225 ah when discharged at a higher rate. (in 10 hours, for example) You can expect an additional loss in the above application. (the faster the discharge rate, the less available battery capacity)
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YC 1
Yuba City Calif.
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Great response hopefulbob. I hope you save that so you don't have to re-do it in the future.
My parents ran a freezer and fridge this way for several years while fulltiming. They ran an 1800W inverter and managed quite well. When they had 110 they would switch to that.
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djmiranda1
Downey, CA
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hopefulbob,
I found a sanyo fridge today at costco that draws 0.9amps. According to your calculations with a 50% duty cycle I should be able to run the fridge for approx 21 hours before needing to turn the generator on. I this correct?
Thanks
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deviousracing
mesa, az
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in my opinion, i would not run one off an inverter, my gut tells me that you will have dead batterys all the time, making the camping experience a pain in the ass...
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smkettner
Southern California
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You will probably need to recharge at least two hours per day. But probably two to three hours twice a day depending on other usage also. And that assumes the 45 amps is a three stage converter getting the voltage up 14.2+. If it gets cumbersome you will need a couple more batteries and 80 amps charging. I assume you understand when it says 1.2 amps that it will be 15 amps out of the batteries.
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hopefulbob
Wichita, KS USA
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djmiranda1:
Correct....21 hours. If starting with warm fridge (warm contents?), fridge will run continuously until it and contents are cooled to the set temperature. This could take several hours with a lot of warm contents. Once stabilized, I'd guess that the duty cycle to maintain this temp. would be in the order of 30%, unless you keep opening the door or have 100 deg. ambient.
More good news....Using the .9 amp Sanyo fridge, you would one-half discharge your batteries in 20 hours (no other loads). That's 1/2 of the discharge rate used in determining their 225 ah rating. Expect more than 225 ah from your fully-charged batteries at this lower discharge rate. (peruse "Peukert Effect" for details)
With the Sanyo fridge, sounds like a good, workable system, using your present batteries. The 1.5 amp fridge would be pushing things without added battery capacity.
I operated a 1.2 amp deep freezer in my DP for about 5 years with a 450 ah battery bank. Had no problems except remembering to recharge every 2 days when not traveling in order to keep things cold. You will need to recharge daily.
If you locate your fridge in a cabinet or in any location where its condenser coils are not fully exposed, you must provide forced air flow over the coils. I used a 120 vac computer cooling fan blowing over the coils. Wired it through the freezer thermostat, so that fan ran only when when freezer was running.
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bkirkpatrick
Brea / Orange County, CA
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deviousracing wrote:in my opinion, i would not run one off an inverter, my gut tells me that you will have dead batterys all the time, making the camping experience a pain in the ass... Bingo. Get a Honda EU2000 and run it all weekend on a couple of gallons of gas.
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djmiranda1
Downey, CA
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I don't think I would like to run the generator 24/7. Ok the other hand I think I'll just plug the fridge into shore power before the trip and swtch to inverter when on the road. Being that the average temp is like 60 during the riding season I don't think the fridge will be cycling on very often. I will run some test before I install the fridge for good.
Thanks for the input,
-David
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