How Long Will Refrigerator Run

[masterdrago]

We'll be taking our first trip soon and I concerned about the refrigerator. It's a Samsung 18 cu ft that has a max current of 3.0. I looked at the batteries which all I can tell is tag with 27DP, cca@0F 650, mca@32F 800, 23amp ave 175min. I don't know what all this means but it is useful to someone. There are two of these new marine deepcycle/starting batteries in the big plastic sealed box wired parallel. Our trip to the first camp site will be ~4-5 hours. I suspect the current draw on the ref is less than 3 amps (my years of working on these show more like 1.5 amps) and that duty cycle will be about 60% with the ambient temperatures we have right now. My question is will I arrive with dead batteries and a non running refrigerator?

I've looked at some other batteries (Trojans) but these are brand new (9/17 & 10/17 dates) and a pair of the big 6 volters wired series doesn't look to give much more amp hours. Please give me some pointers and correct me where I'm wrong.

[jpcoll01]

4-5 hours, get it cold before you leave and leave it off while you travel. or at least 1/2-2/3 of the way.  Save your batteries and your stuff will stay cold/frozen.

[Mike and Claudia]

Welcome to RVing!!

If you will GOOGLE:  The RV side of Life part 1 & 2.  I know that this is s "foreign Language" but if you will study these, you will soon pick up on this new "language" and be speaking it fluently in no time.  

Good Luck, and DON'T be afraid to ask questions!
!

[NDBirdman]

I am now curious about same question.  Fridge runs off battery and/or LP.  (mine)  If I set it to run off battery going down the road, you said 4-5 hours.  With the camper connected to the truck, will the 12 volts from the truck's system charge the battery going down the road, or are they not connected?  If not, is there a way to connect the campers bat. system to the trucks so it can charge/run camper 12 volt system while connected?

[JimK]

Some key information is missing.  Starting with the batteries, we need to know the AH capacity.  I would guess about 80 AH per battery.  So drawing 2 batteries down to 50 percent means you can pull 80 AH.  Next, we are to assume these batteries will not be charging during the travel period?  Next there is uncertainty on the draw of the refrigerator.  I assume the 3 amp pull which you claim to be 1.5 amp is at 120 volts.  The 12 volt amperage will be 15-30 amps.  For a 60 percent cycle that means about 10 amp per hour for you 12 volt batteries.  So it should take roughly 8 hours to deplete your batteries half way.  You should be fine and have a safety margin of several hours.  Why not do a test in advance?  You will need a volt meter but you should have one anyway in order to monitor your batteries. 

[Yarome]

Those numbers are for a Duracell duralast 27DP hybrid deep cycle. It's the smaller 650CCA model so you should have around 65ah's per (130ah total). Ideally, you don't want to take them down more than 50% of capacity so you'll be looking at the 65ah's to work with. 

You don't want to forget that you'll have a parasitic/phantom draw of around 24ah's per 24hr period. From there it should be easy enough to calculate your available hours of operation.

[Yarome]

2 minutes ago, NDBirdman said:

I am now curious about same question.  Fridge runs off battery and/or LP.  (mine)  If I set it to run off battery going down the road, you said 4-5 hours.  With the camper connected to the truck, will the 12 volts from the truck's system charge the battery going down the road, or are they not connected? 

It's more likely that you have a 2-way reefer. 120vac or LP. There ARE 3-way reefers (120vac/12vdc/LP), but not all that common. I am also unsure when you said "off battery" if you might have meant off battery via an inverter to supply 120vdc. If "that" happens to be the case then you will NOT want to run your reefer "off battery" when not connected to shore power. Us the LP setting. 

Using either 120vac OR LP you are still using a small amount of 12vdc. The control board operates on 12v... either from your converter while plugged in to shore power or from your batteries when unplugged.

As for your "connected while driving" question. That depends. Some setups do provide a very minimal "maintanence" charge. Meaning... your batteries shouldn't go down much at all while driving. Some do NOT. You would need to check your pigtail connector to see if 12v is feeding to the "hot" wire.

The last part... I'll let someone else touch on. It get's quite lengthy.  In a nutshell... Yes. It's possible. What it generally boils down to though is, "is it practical?".

[Kirk W]

42 minutes ago, masterdrago said:

I suspect the current draw on the ref is less than 3 amps (my years of working on these show more like 1.5 amps) and that duty cycle will be about 60% with the ambient temperatures we have right now. My question is will I arrive with dead batteries and a non running refrigerator?

Since you have a 120V refrigerator it draws 3a of 120V that is supplied from an inverter which has to draw about 10 times as much from the 12V batteries to supply the power or about 10a of power from the batteries. But the good news is that it only draws the current when the compressor is running which will be only minutes per hour if that much. It should be no problem at all, and the tow truck will be supplying some recharge power to the batteries keeping them charged.

8 minutes ago, NDBirdman said:

I am now curious about same question.  Fridge runs off battery and/or LP.  (mine)  If I set it to run off battery going down the road, you said 4-5 hours.  With the camper connected to the truck, will the 12 volts from the truck's system charge the battery going down the road, or are they not connected?  If not, is there a way to connect the campers bat. system to the trucks so it can charge/run camper 12 volt system while connected?

You have an RV refrigerator and it uses only a tiny amount of 12V power to operate the control circuits. It uses propane for the cooling energy and when shore power is available it uses 120v alternating power for cooling. The 12V controls must have power in either mode but the amount is very small. 

In nearly all cases the tow vehicle does supply some power to recharge the RV batteries but due to the wire size in your harness that power is pretty limited and if you spend nights dry camping the wire size may limit current to a point where it doesn't fully charge while traveling. For that reason, many RV owners add an extra charging line of a much larger size to do a better job of charging but if all that you are using is your refrigerator, it should easily keep up. 

[NDBirdman]

Thanks for the answer to my query.  Mine has a selection of LP/Elec.  I believe ya'll are right, I have choice of LP or shore power, one selection says Auto.  If I select auto, then going down the road it will run on LP, correct?  If so, it would probably run until both LP tanks are empty so I have nothing to worry about I assume.

I have alot to learn and hate it is sitting in the driveway, covered in snow now... I want to get out sooooo bad!

 

[Yarome]

1 minute ago, NDBirdman said:

...then going down the road it will run on LP, correct?  If so, it would probably run until both LP tanks are empty so I have nothing to worry about I assume.

Correct. And... correct. You're good!

[Kirk W]

4 minutes ago, NDBirdman said:

If so, it would probably run until both LP tanks are empty so I have nothing to worry about I assume.

It would run until the batteries run down below 10.5V or you run out of propane. 

[Yarome]

22 minutes ago, Yarome said:

Those numbers are for a Duracell duralast 27DP hybrid deep cycle.

I edited the above due to unexpected fog in the brain pan.  Pulling 3amp on 120vac via your inverter would actually be pulling ~35amps of 12v (actual draw + overhead). With 65ah's available you would have roughly 1.8hrs of continuous run time. 15min/hr of actual would put you out to 7hrs. 

[NDBirdman]

Cool, thanks ya'll.  I should be good, I plan on putting in a couple banks of 6v golf cart batteries and a solar panel or 2.  We plan on doing some boon docking eventually.

[Yarome]

8 minutes ago, NDBirdman said:

Cool, thanks ya'll.  I should be good, I plan on putting in a couple banks of 6v golf cart batteries and a solar panel or 2.  We plan on doing some boon docking eventually.

Probably should have mentioned... (not that you're ever going to burn off an entire tank while driving from A to B), but it may not necessarily be both tanks. Some regulators are auto switching. Meaning... both tanks are/may be "in play", but if you have a manual switch you have to physically switch your tanks over when one runs dry.

[NDBirdman]

Mine is auto switching.  :-)

[masterdrago]

Okay, thanks for all the help. 1st off let me say I've been working on a/c and domestic refrigerators since the early '70s. I understand E=IR, P/V=I, blah, blah, blah, etc. I do not know the AH of these batteries. What I could see marked on the top of them is what I quoted in OP. The refrigerator is not LP. It is a domestic household 18 cu ft Samsung. The name-tag max current is most likely when in defrost mode and running one of the heaters. From my long experience and most recently working to repair Samsung, LG, GE, Whirlpool, and Sears refrigerators, I do not need to put an amp probe on it to know that about 1-1.5 amps will be drawn during a cooling cycle. Most now have very efficient variable speed compressors run by an inverter board.

The TV does supply some charging current when running (not sure how much), I'm sure of since when I found the disconnect "key" not in and the battery vdc was 12.3 and came up to 12.9 while connected to the TV running.

The info missing is what the batteries are capable of giving during the 4-5 hours on the road. AND, will they be exhausted when we get to camp? One other question that has crossed my noob cranium is how bad is it for the 12vdc stuff to hook to shore power AND the TV at the same time? -- two charging systems trying to get something into the batteries - alternator & converter Progressive Dynamics thingy?

So, in theory, a short 4-5 hour trip in not hot weather, if unit is well cooled b4 trip, then things should work okay. Maybe not hurting anything to add a big bag of ice to a pan in the reefer.

[lenp]

If you could beef up the charging line from the TV you would get a few more amps back to the trailer and probably keep the batteries fully charged.  OR, install a couple of solar panels on the roof.

I have 750 watts on the roof that will supply all my needs (including the Samsung refer) if I can get 4-5  hours of sun every day.

Lenp

[jcussen]

Not sure how you are wired, but often charging line from tv will be diode protected [current only goes from alternator to tv and trailer battery when tv running.but not connected when not running. This is to protect your tv start battery from being discharged by the trailer. Would dump the battery boiler [progressive dynamics] and get a smart charger. 

Agree with Yarome, maybe 1.5 or 2 hours max. depending on charge current from tv.

Agree with lenp, solar panels are cheap now, and they work running down the road or when parked.

Just to be clear, 1.5 to hrs run time, if not running only what inverter draws

[Yarome]

12 hours ago, masterdrago said:

The info missing is what the batteries are capable of giving during the 4-5 hours on the road. AND, will they be exhausted when we get to camp?

Um... already mentioned twice... each of your batteries has the max storage capacity of 65 amp hours (ah). That would be at the manufacturers peak storage rating when new and at 100% SOC (state of charge). 2 batteries in parallel would be a total capacity of 130ah's. 

19 hours ago, Yarome said:

Pulling 3amp on 120vac via your inverter would actually be pulling ~35amps of 12v (actual draw + overhead). With 65ah's available you would have roughly 1.8hrs of continuous run time. 15min/hr of actual would put you out to 7hrs. 

"Available" being 50% of total capacity in order to maintain battery health. If your load during a cooling cycle is actually only 1.5amps.. those numbers would double.

If your TV is supplying some amount of 12v to your battery bank while driving... those numbers would increase even further. 

4-5hr's on the road.... no problem. Ice is not necessary, and as jpcoll01 said.... it's not really even necessary to run it for that short of a drive. If it isn't opened it should have no problem keeping your "stuffs" chilled.

For around $20 you can purchase a remote temp monitor. Stick that in your reefer and monitor internal temps remotely. If it drops below your comfort zone... crank it back on.

 

[remoandiris]

Your Samsung fridge will stay cold for AT LEAST 6 hrs with NO power going to it.  I have the same fridge and have experimented by turning off the inverter when traveling just to test the limits of the fridge.  Now I know if the inverter craps out, I can take my time to research a replacement instead of worrying about it and buying in a rush.  

[Al F]

19 hours ago, NDBirdman said:

Cool, thanks ya'll.  I should be good, I plan on putting in a couple banks of 6v golf cart batteries and a solar panel or 2.  We plan on doing some boon docking eventually.

Before your change out your batteries and throw on a solar panel or two, read and understand the links below.  It will save you lots of headaches when you do decide add battery power & solar.   Also practice you boondocking skills when you have hookups.  All you need to do is disconnect from the shore facilities.

The 12volt Side of Life (Part 1) Batteries

The 12volt Side of Life Part Solar & Inverters

Jack Mayer RV Electrical

Jack Mayer Battery & Charging

RV Dreams Electrical Information site

RV Dreams Electrical System

HandyBob's Blog Solar & Elect

[Kirk W]

11 hours ago, masterdrago said:

So, in theory, a short 4-5 hour trip in not hot weather, if unit is well cooled b4 trip, then things should work okay.

I am sure that it would be fine and probably you could go that long with the refrigerator turned off when previously properly cooled if the door is not opened at all. Many RV owners who have the typical RV refrigerators do this because they don't like to use propane while traveling and frozen foods do not thaw. 

[Yarome]

18 minutes ago, Al F said:

The 12volt Side of Life (Part 1) Batteries

The 12volt Side of Life Part Solar & Inverters

Jack Mayer RV Electrical

Jack Mayer Battery & Charging

RV Dreams Electrical Information site

RV Dreams Electrical System

HandyBob's Blog Solar & Elect

That about covers it! ;-) I wish we could get "the powers that be" to sticky these links. Even if you aren't planning on solar it's information that anyone with an RV would benefit from perusing.

[masterdrago]

13 hours ago, jcussen said:

<snip> Would dump the battery boiler [progressive dynamics] and get a smart charger. <snip>

jcussen, why would I dump the Progressive Dynamics? It's a 75 amp 4 stage (boost 14.4vdc, normal 13.6vdc, storage 13.2vdc, & equalization 14.4vdc) a/c-d/c distribution panel.

Thanks. Lots to learn here. Thanks Al & Sharon for the reading material. Lots of good stuff. Read through most of it one time - now my head is spinning. Inverter, converter, transfer switch, charger - and no wiring diagram for this Montana 3791RD found anywhere. Sometime this week, I'll run a test on the system without shore power. I'll monitor both sides of the inverter to see what is happening. I don't have a d/c amp meter but will be able to watch a/c amps, a/c volts and d/c volts at the same time. I can estimate d/c amps but not the loss through the inverter. I'll also monitor the reefer temps and status.

And yes, the temp in the reefer should be okay for a 5 hour ride since the ambient is so cool right now.

 

 

[Yarome]

13 hours ago, jcussen said:

Would dump the battery boiler [progressive dynamics] and get a smart charger. 

Just a point of clarification here. Generally speaking, Progressive Dynamics ARE "smart chargers" and considered some of the best on the market when it comes to a DP (distribution panel) converter/chargers... and have one of the strongest customer service reputations.