Sprinter-Forum    
 

Go Back   Sprinter-Forum > Sprinter-Based RV's & Conversions > Sprinter RV's & Conversions Talk

Sprinter RV's & Conversions Talk Common features found in Sprinter RV's and Conversions.


 
Thread Tools Display Modes
Old 09-01-2019, 02:41 PM   #11
Shackleton
 
Join Date: Mar 2018
Location: USA
Posts: 10
Thanks: 3
Thanked 1 Time in 1 Post
Default Re: problem with Dometic cfx fridge OR solar power system?

And here are a few more screenshots, including a couple of the Dometic app.
Attached Images
File Type: jpg low_light--glitchy--off.jpg (129.1 KB, 58 views)
File Type: jpg low_light--glitchy--on.jpg (128.3 KB, 57 views)
File Type: jpg low_light--working--off.jpg (130.0 KB, 55 views)
File Type: jpg low_light--working--on.jpg (129.8 KB, 57 views)
File Type: png night--volts_at_fridge--2.PNG (125.6 KB, 56 views)
Shackleton is offline   Reply With Quote
Old 09-01-2019, 03:13 PM   #12
bbax
 
Join Date: Jul 2019
Posts: 4
Thanks: 0
Thanked 1 Time in 1 Post
Default Re: problem with Dometic cfx fridge OR solar power system?

I would run dedicated positive and negative wires from frig to battery. Double the wire size and put a fuse in the middle of the positive side. bypass all connections to anything, direct wire to the refrigerator only. You could be seeing a voltage drop due to terminal corrosion or under sized wire. Do you have a direct ground wire or is the ground connected to the frame? There could be lots of little problems that all add up. You can figure out the proper wire size by measuring wire length and looking at charts to determine proper size. In the aviation world it is common knowledge that most electrical problems are ground wire problems. Lots of ideas here but bottom line is eliminate complexity and do your trouble shooting.
bbax is offline   Reply With Quote
Old 09-01-2019, 04:12 PM   #13
cc_windsurfer
 
Join Date: Nov 2017
Posts: 138
Thanks: 35
Thanked 53 Times in 37 Posts
Default Re: problem with Dometic cfx fridge OR solar power system?

The cable supplied by dometic has pretty high series resistance. Combine that with a dicey connection and you will get the problem you are describing. In my installation I am running 10g from the fuse block to the fridge, then spliced that to the last 3" and connector from the dometic cable; this gives me a more stable voltage on the fridge display.
cc_windsurfer is offline   Reply With Quote
The Following User Says Thank You to cc_windsurfer For This Useful Post:
Midwestdrifter (09-01-2019)
Old 09-01-2019, 06:21 PM   #14
autostaretx
Erratic Member
 
autostaretx's Avatar
 
Join Date: Sep 2006
Location: Seattle
Posts: 18,525
Thanks: 3,230
Thanked 8,527 Times in 6,182 Posts
Default Re: problem with Dometic cfx fridge OR solar power system?

Looking at your screen grabs, the best solar charging current (to the battery, not the from-panel number) is 6.5 amps. (2:25 time point, first screen grab of your series)
You reported that "near 50%, an hour of sunlight brought it to 100%" .... that's only 6.5 amp hours!?!?
(i may well have missed a better charge rate image, they all began to blur...)

I fully agree with the others: you have a high-resistance point (or points) between the battery and the fridge.

--dick
__________________
2005 T1N 118" Freightliner 2500 Passenger Wagon (2.7L, 15" tires, standard (short) roof)
Get YOUR Sprinter's full configuration datacard by entering your VIN to https://www.datamb.com/
http://diysprinter.co.uk/reference <-- lots of service documentation, Thanks to Jens Moller and Arnie_Oli
((as always: this post may go through a couple of post-posting edits... so maybe give it ten minutes before commenting))
autostaretx is online now   Reply With Quote
Old 09-02-2019, 02:00 PM   #15
HarryN
 
Join Date: May 2010
Location: Pleasanton, CA
Posts: 2,679
Thanks: 659
Thanked 871 Times in 708 Posts
Default Re: problem with Dometic cfx fridge OR solar power system?

Hi, can you post a link to the data sheet of your batteries?

Some types of Li batteries have an operating voltage range of ~ 10 - 12 volts, while others are more like ~12 - 13 volts.

The reason that I ask is that there are some popular consumer products that contain Li batteries which operate in this lower voltage range.

The refrigerator compressor is designed to operate in the ~ 12 - 15 volt range (at the terminals). Turning off the alarm doesn't change this, it just disables the alarm.

BTW - do yourself a favor and ditch that renogy solar charge controller - they are ......not all that great.
__________________
Power systems for conversion vans and emergency preparedness.

https://wirlnet-inc.square.site
HarryN is offline   Reply With Quote
Old 09-02-2019, 03:14 PM   #16
elemental
 
Join Date: Jul 2017
Location: USA PNW
Posts: 547
Thanks: 224
Thanked 356 Times in 239 Posts
Default Re: problem with Dometic cfx fridge OR solar power system?

Quote:
Originally Posted by Shackleton View Post
The voltage at the fridge according the the fridge's app is usually 12+, then drops down to 10.8 or 10.7 as it starts up. BUT... last night I saw it drop to 9.6 before the fridge shut off. It's the first time I've seen that happen. The fridge's safety cutoff is 10.1. It didn't give me the warnings (blinking LEDs, app message), just shut off.

The controller has never shown the volts at the battery as lower than 12.

So...

If the fridge turning on is driving the voltage at the fridge below its cutoff value, how do I fix it?
And why has the problem become worse over time?

I'll attach screenshots of the Renogy app.
Others have already responded with good recommendations. I'm just chiming in with a little more background in case electrical wiring isn't something you are friends with:
  • Resistance in a circuit causes voltage to drop (the greater the resistance, the greater the drop), just like a constriction in a hose will cause the pressure at the end of the hose to be less than at the start of the hose:
    • All wiring has resistance; the longer the wire and the smaller the wire, the more the resistance.
    • All connections have resistance; the poorer the connection the more the resistance (not tight, oxidation/corrosion, not clean (foreign matter other than oxidation/corrosion), undersized terminals)
    • Other circuit elements like fuses/breakers also have resistance and cause a voltage drop
  • All loads on a wire cause a voltage drop; the greater the load (the more energy used by the load), the greater the voltage drop

If the refrigerator is malfunctioning in a way that increases its energy consumption, it could be causing a bigger voltage drop than expected and triggering its own cutoff. In general, malfunctions can exhibit degradation over time (a slope) rather than a step function (cliff). I don't know how likely a refrigerator compressor is to exhibit a malfunction in this way.

Your notes indicate that the voltage seen at the refrigerator is less than that seen at the battery, which is normal and expected. However, the amount of this drop could be too much to maintain the required voltage at the refrigerator when it is running (even without the refrigerator having a malfunction). Your wire size and run length isn't changing, but problems with your connections (loose, oxidizing/corroding) can worsen over time. If the wiring from the battery to refrigerator is marginal (gauge and run length just barely on the "good" side of enough voltage to run the refrigerator, then the effects of increased resistance from loose/oxidized connections will be heightened.

It would be useful to measure (with a known good multimeter) the voltage at the start of the refrigerator circuit (point where the refrigerator circuit is connected to the house electrical backbone) and the voltage at the end of the refrigerator circuit (measured at a point on the refrigerator circuit board where the power enters). The difference would give you a measurement of the voltage drop in that wiring, which will give you an indication of whether you should look at the wiring first or the refrigerator first.

And as others have already said, if the problem is in the wiring then you have to do things to lower the resistance in the wiring. Things like increase the size of the wire, decrease the run length of the wire, improve connections (clean and tighten them). If you are depending on a chassis ground then the vehicle is part of your wiring, which you could eliminate by adding a circuit "return" wire (ground) that connects more directly to the battery negative post (ground, at least for most contemporary wiring schemes).

If the problem is in the refrigerator and it is getting worse over time, it will probably fail altogether even if connected directly to a big power source. Waiting for that failure could be costly; finding someone who can demonstrate to the warrantor's satisfaction that the refrigerator is acting out of spec would be better.
__________________
--
2017 Sprinter 2500 170 Crew OM642 5-speed auto with Adventure Wagon interior&MOAB
elemental is offline   Reply With Quote
Old 09-06-2019, 02:50 PM   #17
Shackleton
 
Join Date: Mar 2018
Location: USA
Posts: 10
Thanks: 3
Thanked 1 Time in 1 Post
Default Re: problem with Dometic cfx fridge OR solar power system?

Thanks for the great summary, Elemental.

Right now the system is back to running fine. But there's still a ~2 volt drop at the fridge - as reported by the fridge's app - when it kicks on. Seems like a lot, but it's fine if that circuit is starting at 12.3 volts or more. If the starting voltage is lower, the drop will take it down below the fridge's automatic cutoff level.

I now have a sense of what to watch, and I have baselines for everything. It could be that everything is fine as long as the battery gets fully charged during the day, and I just had a string of days in which I parked in the shade too much. So I'm going to keep trying to find a pattern.

I'm on the road, so trying to avoid having to take the thing apart - much less rewire the circuit - unless it's clear that's the solution.

Thanks, everybody.
Shackleton is offline   Reply With Quote
Old 09-06-2019, 05:46 PM   #18
HarryN
 
Join Date: May 2010
Location: Pleasanton, CA
Posts: 2,679
Thanks: 659
Thanked 871 Times in 708 Posts
Default Re: problem with Dometic cfx fridge OR solar power system?

What is an OEC Li battery pack?

I could not find it using various search methods on line.

Thanks
__________________
Power systems for conversion vans and emergency preparedness.

https://wirlnet-inc.square.site
HarryN is offline   Reply With Quote
Old 09-06-2019, 11:36 PM   #19
Shackleton
 
Join Date: Mar 2018
Location: USA
Posts: 10
Thanks: 3
Thanked 1 Time in 1 Post
Default Re: problem with Dometic cfx fridge OR solar power system?

HarryN, OEC is Overland Energy Co.
Shackleton is offline   Reply With Quote
The Following User Says Thank You to Shackleton For This Useful Post:
HarryN (09-20-2019)

Tags
dometic refrigerator, problem, solar power

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT. The time now is 04:31 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2020, vBulletin Solutions, Inc.