Dometix CFX 50W Normal or Problem?

[jg45]

I recently purchased a CFX 50W from Dometic directly when they were having their memorial day sale. Upon receiving it, I plugged it into the 12v outlet in the rear of my Xterra and fired it up, turned on WiFi and opened the app. It initially shutoff not long after compressor start and the voltage reading in the app was below the 11.4v medium battery protection level. Interestingly, checking voltage at the battery showed it to be 12.4 v. Suspecting the wiring was too small to the factory port, I ordered and installed the ARB wiring fridge wiring kit. That kit contains 10awg wire with the ARB outlet to plug into. I installed this kit yesterday wired directly to the battery. I also charged the battery (Optima red top) fully and then had it tested. I am still seeing running voltages around .6-1v lower than the measurement at the battery at the same time. Is this normal?

 

[Chad D.]

You’ll absolutely see a voltage drop if the run is a significant distance. Larger wiring helps, but I’m. It terribly surprised to see the drop you describe if the run is over 20’ or so.

I also have 10ga from my battery to the outlet, with a total run length of just over 20’. I’m a solid half volt, plus, lower at the outlet than at the battery.


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[llamalander]

Poor contacts in a plug (especially the lighter type) will drop your voltage as well. If you wire the cord directly into your fuse panel/ battery bank, that might help. The plug into the fridge is the only one you need to remove when the fridge is not in the vehicle.

 

[jg45]

Thank you for the input. The ARB outlet is wired directly to battery. Total run is about 18 feet. The outlet itself looks like a cigarette lighter, but is actually a two prong connection that the power cord from the fridge connects to then screws in to lock into place.
The charts I've looked up say that at 7A and 18 feet, at 12v the voltage drop on 10awg should be .25V. However the drop I'm seeing is as reported by the Dometic itself and is closer to 1v which messes with the low battery protection built into the fridge.

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[67cj5]

Over that distance most guys run 8g or even 6g cable would be better, I have known some folks to even use 4g,

I look at it this way, We pay a premium for these fridges yet we skimp on the wiring due to the cost of the cable, It's a bit like putting cheap Oil in to a $30k motor, Ya just wouldn't do it and engine like that deserves the best as so does your fridge,

Don't get me wrong because I love ARB gear but their wiring kit is really only any good if your fridge is less than 8 feet from the battery and even then I would be going heavier,

Hope that helps.

 

[e60ral]

use a voltmeter and physically measure the voltage at the plug yourself to confirm the measurement the fridge is seeing

The charts I've looked up say that at 7A and 18 feet, at 12v the voltage drop on 10awg should be .25V. However the drop I'm seeing is as reported by the Dometic itself and is closer to 1v which messes with the low battery protection built into the fridge.

is 18' the total circuit distance (battery to fridge to battery) or is it one direction?

 

[jg45]

The 18 feet is the 20ft ARB wiring harness with about 2ft cut off. With a freshly charged battery, engine off, fridge on, I am reading 12.42v at the battery, 12.26v at the socket the fridge plugs into, and 11.8v is being reported by the fridge itself.



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[67cj5]

The 18 feet is the 20ft ARB wiring harness with about 2ft cut off. With a freshly charged battery, engine off, fridge on, I am reading 12.42v at the battery, 12.26v at the socket the fridge plugs into, and 11.8v is being reported by the fridge itself.



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12.42v Is a bit low for a freshly charged battery, my Lead Acid deep cycle batteries read about 13.32 to 13.38v after a rest when they have finished charging, I'd guess that your battery is either not charging up properly which means you need to fully charge it on a smart charger and then as soon as it has finished charging Hit the Repair mode, and it that does not work then replace the battery,

Here's why,

At 12.42v My ARB 47L/50Qt during it's ON Cycle would make that Voltage drop down to around 12.02 to 12.08v and as soon as it switched in to Sleep Mode the battery would Recover back up to 12.39 to 12.40v, One of my single 115A/h Batteries won't show 12.46 volts until it has been running my fridge for about at leased TWO days maybe even three day if the weather is coolish.

So In YOUR case you have 12.42 at the Battery, 12.26v at the Socket, Which means under load "On Cycle" Your 12.26v is dropping down to around 11.86v maybe less because of the distances it has to travel to reach the Fridge, So being around 11.86v your battery is already right on the edge of the higher cut off point for most fridge's So check in your fridge manual and let us know what the cut off voltages are for Low Med and Hi,

Also what type of Charger are you using, The reason I ask is the old linier type chargers are great for dumping Bulk Amps in to a battery Like what you need when you out Camping Off Grid, but when you are around the Burbs or have access to a Hook UP and have a good half a day to let the battery charge properly then a Smart Charger needs to be the Weapon of Choice,

Sounds to me like your Battery has just got lazy and needs a kick up the ******$$$ with a good quality Smart Charger, I Hate Em but this is one area they come in to their own.

Hope that helps, good luck,

 

[jg45]

Thanks. I thought there battery voltage seemed low too. I charged it with a Schumacher sc-1200a. Supposed to be a smart charger. I also took it to Advance and they ran a test and said battery and charging system are fine.
Is it normal for the fridge to report voltage that is over 0.5v lower than the voltage at the socket it is plugged into? That is really what in trying to find out. It just seems is for there to be that much difference between the socket it's plugged into and what it time it has

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[67cj5]

Thanks. I thought there battery voltage seemed low too. I charged it with a Schumacher sc-1200a. Supposed to be a smart charger. I also took it to Advance and they ran a test and said battery and charging system are fine.
Is it normal for the fridge to report voltage that is over 0.5v lower than the voltage at the socket it is plugged into? That is really what in trying to find out. It just seems is for there to be that much difference between the socket it's plugged into and what it time it has

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YES and maybe No, The fridge's meter/software was calibrated and setup at the factory but it is anyone's guess how spot on they read, add to that your multi meter again How spot on does it read and trying to find two meters or Dials that read the same drove me to buying the best on the market, In most cases you can get by with taking your multi meter some place and getting it calibrated or at leased get them to check it and tell you how much it is out and when you use it Add or Subtract that amount from your tests, cheapest way it to find a person who works for the National Grid and get them to check your meter with theirs because theirs are checked and Calibrated every 6 to 12 months. and just take a new small 9v Battery along as a test piece and then you will know the answers, Multi meters/Volt meters are a curse, and I have spent some good Coin on getting to the truth and getting it right.

Ya know back a few years ago when solar panels were on my mind I had a heap of multimeters and I could not get any of them to display matching reading and it drove me nutz, so I when to Fluke importers and bought the most top of the line model, Problem solved,

At present I still have that meter and I have a proper sonic type battery tester that gives me a print out of the batteries condition etc which is on par with the fluke, I also have a mid range/priced multi meter which reads within 0.05v and I have one of those power anyalizer things from ebay which although they display all the right numbers on all it's other read outs, Due to the battery being in a battery box the Power doodad can read slightly Hi or Low on the volts.

What sort of a Tester did those guys use because a Drop Test / Direct Short type load tester only shows you if the battery can hold a charge or not, Where as a Sonic tester will show the Voltage and the SOH/State Of Health, and the CCA/CA etc and the batteries Resistance and a heap of other stuff, AGAIN, I had another issue a few months back by being sold the wrong batteries so I bought the sonic tester and this told me that they were selling the wrong batteries,

My point is that fridges are one thing and Wiring is another and to make things worse Batteries are in a world of their own and trying to match all THREE is a nightmare, hence the Fluke and the Sonic Tester, because they told me about the wiring and the power supply/drain but most of all the Batteries, And for the sake of a $100+ bucks that Sonic tester is worth it's weight.

Sorry for the long winded reply but to get it spot on you have to either jump right In or just get it close enough and be happy with that.

So Yes it is normal to see a different reading from the fridge compared to the multi meter at the socket etc again How accurate is the multi meter and how accurate is the meter in the fridge ??,

What bothers me the most is why are those guys telling you that a battery fully charged at 12.42v is in good condition ?? and if so Then I would then say that your multi meter is reading at leased 0.8 volts too low, So either the battery is knackered or the meter is ?? Because if you have 13.2v at the battery using your figures you should have around 12.8 to 13v at the socket, If your battery is as good as those Guys said it is, ??

hope that helps,

 

[jg45]

Thank you for the thorough reply. Very helpful info. My meter is a Fluke that I bought many moons ago. I don't know how well it's calibrated. That's something I need to get checked.
The Advance Auto used this big handheld digital battery tester. I don't recall the brand or type, but it gave a pretty thorough print out of the battery and the charging system.
I'll take it to a different store and have it checked again.

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[67cj5]

Thank you for the thorough reply. Very helpful info. My meter is a Fluke that I bought many moons ago. I don't know how well it's calibrated. That's something I need to get checked.
The Advance Auto used this big handheld digital battery tester. I don't recall the brand or type, but it gave a pretty thorough print out of the battery and the charging system.
I'll take it to a different store and have it checked again.

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Cool No Worries, I had a battery on a 15 Amp smart charger last night and they are slow but 5 hours after I disconnected the battery still reads about 13.30 Volts as do my other batteries, Baring in mind that these batteries are nothing special just off the shelf 115A/h Deep Cycle batteries as in Wet Lead Acid and the one I just charged is 2 years old this month, So nothing to write home about there,

So taking the above in to account I am thinking that having a voltage reading of 12.42v is a bit of a worry, I think you need to buy the Gizmo that I bought and it will tell you what is going on with the Battery and the charging system and the starting system etc, so if you want the link just let me know, But 12.42v is not right Like I said my battery reads close to that after running my ARB fridge for 2 and a bit days,

take care and good luck.

 

[burleyman]

Keeping a refrigerator alive with a battery and solar panels has brought back memories of my first DC theory from the sixties. Mainly simple series DC circuits. 67cj5 said it well. Looking for voltages in the tenths or hundredths at multiple locations with changing inputs and outputs is tough, even with matching calibrated meters.

I'm old, and my old industrial quality calibrated meters have one-by-one bitten the dust, except for a trusty true-rms Fluke. Amazingly, I have found the cheap sometimes giveaways from Harbor Freight to be quite accurate on DC volts, and most have a simple slotted adjustment on the circuit board for adjusting DC voltage. A local starter/alternator rebuilder has calibrated meters, so I use that and keep at least three meters matching.

Keeping up with voltage drops/power losses in a system with changing values is easier for me by using a llloonngg test lead. A single strand of twentysomething gauge telephone wire about 24 feet long with small alligator clips on each end allows for measuring a voltage drop/power loss from one end of a wire and associated connectors and devices to the other end on my rigs. It's helpful to know the minimum loss at maximum solar output current (amps) or alternator output to recognize an increasing resistance/connection problem. The 24' lead coils to a compact package for easy storage.

There are numerous inexpensive digital meter displays with on/off switches in my van and travel trailer. Display tenths of volts. I've probably ordered about thirty for myself and others. Hook 'em all to a single battery and cull any that don't match. Only two haven't. They're all over Ebay and Amazon.

I now know minimum voltage drops at various points. If they head upwards, start looking. With just accurate dc voltmeters and ammeters, maintenance hasn't been bad in my short four year simple solar experience. I've installed and removed digital smart devices bought just because. If it has a readout, it uses energy I prefer used elsewhere. At night, I want dark and a seldom running fridge.

Using a 12v something with a motor or adding a 15 amp 120vac capable inverter to the mix opens another major voltage drop can of worms. Standard wire sizes and amp ratings from standard house wiring tables fly out the window. It's wonderful pulling in wire for the third time after something trips off due to voltage drop. Low voltage Beep, Beep, Beep, Chirp, chirp, chirp, cry, cry, cry.

The popular solar companies recommended wire sizes are handy.

 

[67cj5]

As a rough guide this chart might help, Noting that it does not allow for the Ambient temperature OR the Battery temperature at any persons location who happens to read this, Although such temperature changes will have a minor effect on these figures, In that we are talking less that 0.10 to 0.20 of a Volt which would cover the temperatures from Siberia to Death Valley, U.S.A. .

As can be seen from this Chart a voltage of around 12.42v places this Battery at about the 76% Charged mark and at 12.26v is equal to around the 57% Charged mark, Baring in mind that to be safe we should only discharge a Deep Cycle Lead Acid Battery down to around the 50% mark which is equal to 12.20v then these figures already place this Battery in to the re-Charge ASAP zone,

Hope that helps,

 

[e60ral]

I'd bet most running fridges are on AGM