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  1. #1
    Site Team Soundsailor's Avatar
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    Sizing the battery bank - How much do we need to support the Furrion12 volt refrig

    We're interested in the drawdown from the Furrion 12 volt refrigerator when used "off-grid". The Furrion manual describes the power use in "off-grid mode" as 5.3 Ah (Amp-hours) when the external temperature is 77 degrees F. That would suggest a battery budget of 127.2 Ah (5.3 x 24) per day. The question is: Does the refrigerator use that much? For instance, the manual suggests that there is an "Off-Grid Vacation mode" which they suggest helps to conserve power usage when disconnected from the grid. But they're not clear if the lower draw is the 5.3 Ah or some other amount. And is the 5.3 Ah an average figure accounting for the time the refrigerator compressor is not working or is it the draw when the compressor is on? This is important in deciding on the size of our battery bank. A lot of our camping is done off the grid. And while we will have solar to recharge the batteries, many of the campgrounds we like the best are heavily wooded minimizing the amount of solar we will get.

    So how to size the battery bank? If we assume 127.2 Ah per day, then to go for an off-grid excursion of five days without any recharge from the sun would take 636 Ah of battery (for reference the battery that comes with the 260RD is 100 Ah but since it is a lead-acid battery it should not be discharged more than 50% leaving an effective budget of 50 Ah, not even enough to run the refrigerator for 12 hours leaving out any other draws on the battery.) Currently, we're planning on 3 200 Ah LifePO4 batteries but are considering adding a 4th. Lithium batteries theoretically can be discharged to 0%, but in practice, they last longer when discharge to no more than 30%. So the 3 batteries we have now would give a battery budget of 3 x 200 Ah x 70% (100% - 30%) or 420 Ah. That might be enough for a little over three days assuming the 127 Ah draw is correct and we don't run too much else off the battery.

    Have any of you done any real-world observations on what the Furrion refrigerator actually uses? Any suggestions on how to size the battery bank? I'm already leaning towards a 4th battery. While we will get some solar recharge even from the shadiest of sites (I'm going to deploy two 100 W portable arrays that can be moved around to be in the sun, plus a 100 W panel in addition to the 160 W panel already on the roof), right now I'm planning on worst-case numbers. We also have a generator (rather not use it due to the noise) and will be employing a 40 A DC to DC charger to allow the TV to charge the batteries when driving.
    Stephen and Judy
    2022 Reflection 150 Series 260RD (Stella)
    2017 Chevy Silverado 2500 HD (Blue)
    Traded - 2018 Forest River Rockwood Minilite 2104S

  2. #2
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    Quote Originally Posted by Soundsailor View Post
    We're interested in the drawdown from the Furrion 12 volt refrigerator when used "off-grid". The Furrion manual describes the power use in "off-grid mode" as 5.3 Ah (Amp-hours) when the external temperature is 77 degrees F. That would suggest a battery budget of 127.2 Ah (5.3 x 24) per day. The question is: Does the refrigerator use that much? For instance, the manual suggests that there is an "Off-Grid Vacation mode" which they suggest helps to conserve power usage when disconnected from the grid. But they're not clear if the lower draw is the 5.3 Ah or some other amount. And is the 5.3 Ah an average figure accounting for the time the refrigerator compressor is not working or is it the draw when the compressor is on? This is important in deciding on the size of our battery bank. A lot of our camping is done off the grid. And while we will have solar to recharge the batteries, many of the campgrounds we like the best are heavily wooded minimizing the amount of solar we will get.

    So how to size the battery bank? If we assume 127.2 Ah per day, then to go for an off-grid excursion of five days without any recharge from the sun would take 636 Ah of battery (for reference the battery that comes with the 260RD is 100 Ah but since it is a lead-acid battery it should not be discharged more than 50% leaving an effective budget of 50 Ah, not even enough to run the refrigerator for 12 hours leaving out any other draws on the battery.) Currently, we're planning on 3 200 Ah LifePO4 batteries but are considering adding a 4th. Lithium batteries theoretically can be discharged to 0%, but in practice, they last longer when discharge to no more than 30%. So the 3 batteries we have now would give a battery budget of 3 x 200 Ah x 70% (100% - 30%) or 420 Ah. That might be enough for a little over three days assuming the 127 Ah draw is correct and we don't run too much else off the battery.

    Have any of you done any real-world observations on what the Furrion refrigerator actually uses? Any suggestions on how to size the battery bank? I'm already leaning towards a 4th battery. While we will get some solar recharge even from the shadiest of sites (I'm going to deploy two 100 W portable arrays that can be moved around to be in the sun, plus a 100 W panel in addition to the 160 W panel already on the roof), right now I'm planning on worst-case numbers. We also have a generator (rather not use it due to the noise) and will be employing a 40 A DC to DC charger to allow the TV to charge the batteries when driving.
    I can't help you with real-world amp draw, but that amp consumption is while the compressor is running. How much the compressor is running is the hard part. If you can afford and fit a 4th battery, I'd go that route regardless. It will come in handy


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  3. #3
    Big Traveler dryfly's Avatar
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    I don't do any off-grid camping but I can't imagine working without a DC amp-clamp meter to measure current. I purchased an inexpensive one off Amazon and have found it very valuable in checking current draw on various 12vdc circuits. This would allow measuring exact current draw of the fridge with and without the compressor running, as well as other 12vdc circuits that would be routinely used, thus allowing for pretty accurate estimate of what size battery bank needed. What would really be cool is equipment that would graph usage over a 24 hr. period.
    2020 Reflection 273MK

  4. #4
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    Awesome questions as we have the same coach and the same issues. My OCD was going mental when i 1st found out that i had a 12v fridge and how would this work on a 2 week vacation not plugged in. We have an additional 400w of solar waiting to go on and 560Ah of Lifepo4 to go in as well. We too do 95% of our camping with no hook ups, we really do not like the generator. We added a Victron Smart shunt to monitor the Volts/amps in and out of the battery.
    I did set the fridge to "off grid mode", turned the fridge on (nothing inside)and noticed the it was drawing 3.5amps, the fridge had been off for 2days with the doors open,(just come back from a plugged in weekend away) but it is only 4 degrees C here at the moment and the inside of the fridge was somewhat cold.
    So i did not do a full test yet but this is what i got with a temp 70amp Lithium battery on board, this is because i had installed a Lithium charge/converter and did not want to damage the lead acid battery.

    No fridge load Fridge load
    13.4v 13.3v
    -1.06amp drain -4.62amp drain
    -14w -62w
    14h batt remaining 16h 54 mins remaining Not sure why this has gained time???

    I am sure you know this but the minus = draw not charge, i have the solar turned off at the moment.

    Initial info, hope to do more at some point, but need to add the rest of the gear.
    Andy

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    Site Team Soundsailor's Avatar
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    Thanks Andy (@SA-Survival), your situation sounds very similar to mine. Just to be clear, it sounds like your frig is drawing 3.5 Amps when running the compressor. Any idea what that translates to over 24 hours?
    Stephen and Judy
    2022 Reflection 150 Series 260RD (Stella)
    2017 Chevy Silverado 2500 HD (Blue)
    Traded - 2018 Forest River Rockwood Minilite 2104S

  6. #6
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    Quote Originally Posted by Soundsailor View Post
    Thanks Andy (@SA-Survival), your situation sounds very similar to mine. Just to be clear, it sounds like your frig is drawing 3.5 Amps when running the compressor. Any idea what that translates to over 24 hours?
    Sorry, i have not run it at all off grid yet, i read your post and tried it today. Plus it will all depend on outside temp, inside trailer temp, the hotter it is, so the more run time it will use to keep the requested temp. It will generate its own heat and i believe the vent is in the bottom front pushing into the trailer, so if the trailer heats up in the summer time, the compressor will work more frequently. So keep it vented/shaded. Looking forward to adding my gear and testing in the yard before a trip.
    Sandra, Andy, Bella
    260RD
    12019 F150
    15' Off road trailer

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    Long Hauler huntindog's Avatar
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    Quote Originally Posted by SA-Survival View Post
    Sorry, i have not run it at all off grid yet, i read your post and tried it today. Plus it will all depend on outside temp, inside trailer temp, the hotter it is, so the more run time it will use to keep the requested temp. It will generate its own heat and i believe the vent is in the bottom front pushing into the trailer, so if the trailer heats up in the summer time, the compressor will work more frequently. So keep it vented/shaded. Looking forward to adding my gear and testing in the yard before a trip.
    I have a Victron shunt/monitor for my battery bank. It is bluetooth so I can see what is happening when under tow. With the wind at highway speed, my fridge runs almost all of the time. It is an 18CF propane/electric one. I run it on electric when under tow, and propanw when camped. It draws 55 amps on electric/inverter. I have enough solar to keep up, so that is not an issue. And I know that this is about DC fridges,,,but the on time when parked is a lot less than when under tow. That will probably be true for DC fridges as well

    I strongly recommend a monitor. It means no more guessing about what is happening. You will know.
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  8. #8
    Site Team Redapple63's Avatar
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    Sizing the battery bank - How much do we need to support the Furrion12 volt refrig

    Quote Originally Posted by Soundsailor View Post
    Thanks Andy (@SA-Survival), your situation sounds very similar to mine. Just to be clear, it sounds like your frig is drawing 3.5 Amps when running the compressor. Any idea what that translates to over 24 hours?
    Let’s play with numbers for a bit…

    Round up to 4amps per hour and 65% duty cycle

    (4 x 24) / 2 = 96 / 2 = 48 amp hours daily, so we round up to 50 then add 20 amp hours because we can = 70 amp hours daily. Add in your number for the other items used daily and that is your daily usage.

    Let’s say for giggles you are at 150 amp hours daily, which I doubt, but go with it.

    You have 420 amp hour capacity with 30% reserve.

    With no input you have a bit less than 3 days.

    Add in 65 per day from your 460 watts of solar (50% at 5 hours = 13amps x 5 or 65amp hours).

    Your daily loss or consumption (420 - 150) + 65 = 75 amp hours.

    This gives you a 5.3 day stretch with the originally stated 30% reserve.
    Longer with a genny.

    That’s my rough math give or take. If anyone has some real values, and better assumptions let’s plug em in.

    Thanks,
    Bill
    2019 GMC 3500 SRW Sierra Denali Duramax
    2020 Reflection 315RLTS

  9. #9
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    The core issue has been mentioned but not emphasized.

    There are too many factors to know how much the cooling system will run.

    • How often do you open the door?
    • What's the room temp when you open the door?
    • How full is the fridge?
    • How much do you add or remove?
    • How warm is what you put inside?
    • What is the outside temp when the cooling is running? (That's what the manual is referring to.)
    • How much wind is blowing across the condenser fins?
    • What's the relative humidity?
    • How tight is the door seal?
    • Is the sun shining on the fridge side wall?


    I've done energy audits on homes and usage factors are just too complex to really pin down. On an RV that goes triple! When all the figuring is done, the wild swings of usage overwhelm most of the other factors. Bill mentions 65% duty cycle, but it could be >85 or <35 on different trips or even different days in the same place. .

    Calculate for 100% and know you'll get at least that long. Or make a guess and know some trips you'll fall short.
    Rick

    2019 Reflection 150 273MK
    2015 Ford F350 CC SB Lariat Powerstroke
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  10. #10
    Site Sponsor Petrovsky's Avatar
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    Interesting how everyone is focusing on only the fridge draw down. Will you not be using lights, water pump, and if cold, heater. I have a 120 VAC/propane 8 cuft fridge from Dometic. I will eventually change to the 12volt system but not before I do a complete analysis of my power requirements. For me, it looks like 2 Battleborn, 2 160 watt solar panels or higher (ideal would be 400), invertor, and most importantly, a honda generator. I agree with the post above concerning the effects on the fridge except that the sun hitting the fridge side has more effect on my fridge than the 12volt due to the efficiency of the system.

    A full analysis of your utilization is in order and that includes everything you use on a daily basis for a week divided by 7 and then multiplied by 15%. Note that you are unlikely to hit 7 full days of sun a peak intensity in all your camping excursions.

    In the fall and the spring the amount of sunlight and inclination depending where you camp will be a factor to consider. Luckily the Li batteries charge fast, and are much lighter than wet cell or AGM's.

    Like I said....I am just starting to analyze my own requirements but I know that I will have to monitor at least a weeks camping this summer in order to estimate my needs. One way I intend doing this is right in my driveway. Plugged in, all power off, batteries disconnected (isolated as I don't want to add converter voltage). Amp meter on incoming line and use each appliance, fan, light, etcetera. I know this will be a/c amps but at least it is a start.

    Good luck and don't forget recharging your usb devices.....
    Pierre & Tara

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