Reefer Run Time Past Issues - Montana Owners Club

masterdrago · 03-12-2018, 10:43 AM

Still trying to understand the refrigerator operation on the batteries (through the inverter). We've taken 3 trips including the shakedown near the house. Did not check reefer off shore power there. On the 2nd trip in December, ref seemed okay on 5+ hour road trip but it was in the 40s. The 3rd trip to Fredericksburg noticed that freezer section had come up to 18 degrees after we got slides open and on shore power (cannot open ref door with slide in). When we returned, I found a loose connection on the 2nd battery. Figured that was the problem.
So just now I've gotten the time to check this out. I'm running permanent 50 amp to RV. When I dropped the house power to the RV and checked, the ref was not running. I remembered reading somewhere on this forum that the inverter has a switch. Found the inverter (hanging on the ceiling in the passthrough basement streetside). 12.7vdc at battery side. Looked around and found the user interface (see pix) and no LED or display. Pushed the power button and shazam. Magic happened. After several minutes of run time the display settled down to showing 12.2vdc and a power of .12 which from reading the Magnum Owners manual is 120 watts. Voltage out is 120vac. So I'm guessing that the clowns at the dealer in October had the inverter off and the clown that bought the RV had no clue (the walk through was not real impressive. I did not even know about the inverter but later found out the 3791RD came with one. What fun. I'm going to let the system run all day and monitor the amps and volts. Will see what the pair of marine deep cycle 12 volt no name batteries will provide. The display showed .04 (40 watts) when the ref first came on. Compressor was not running. The DC amps were 7.2. After a while, the compressor kicked on and the DC amps went to 12.1. I seem to remember that the batteries are ~100AH each. So can anyone tell me how long the estimated time til ref shuts down? Book says 9 hours and the DC shut down says 10.5 volts

jeffba · 03-12-2018, 10:49 AM

answer is depends-- how hot is it in the camper? did you just toss in a slab of
brisket that was a t room temperature?

jeffba · 03-12-2018, 11:05 AM

BTW I have added to my checklist to check to make sure inverter is on after unplugging 120 V from camper.

jcurtis934 · 03-12-2018, 02:13 PM

Fully charged batteries will read around 12.7 vdc after any charging sources is removed and they settle out. Don't want to drag them down below 50% charge, which my brain remembers being 12.2 vdc for flooked aCid batteries aND 12.35vdc for gel batteries. Agm's...not sure. If you take them down below these points, battery life is compromized.

masterdrago · 03-12-2018, 02:58 PM

Today I plan on taking them down to the point that the inverter shuts down (<10.5vdc) mostly as an experiment. Maybe if I significantly shorten their life, I'll have an excuse to get some better batteries. At 11.2vdc, the inverter will initiate a warning alarm and an E05 code. Just curious how long that will take with the refrigerator running about 25-30%. Today is cool - high 62. I doubt the inside of the RV will get that warm.

masterdrago · 03-12-2018, 03:02 PM

I guess I could force 100% run time by asking the reefer to get a temperature that it most likely could not attain. Like 20F below and 28 in frig.

masterdrago · 03-13-2018, 08:29 AM

Going on 24 hours. VDC @ inverter down to 11.9. Reefer run time ~20%. I have it on power freeze now to finish off the batteries shortly. I'll try to monitor closely this morning and will post again.

masterdrago · 03-16-2018, 06:15 PM

I'm sure that this test was not real world because The ambient temps were very mild to cool. The final total hours that the refrigerator ran was between 36 and 40. The real test will come when booking down the highway in mid July across south Texas.

The wattage of these Samsung refrigerators are amazingly low. At various times during the test, checking found 40, 80, or 140 watts being shown by the inverter display. I had turned off the convenience center red battery disconnect key so other 12vdc draws were off. Also of note, I was not connected to the truck charging system.

jeffba · 03-17-2018, 04:14 AM

We have a trip planned in April first leg is "as far as I can go". Will post battery voltages at start of trip and when we finally stop.

masterdrago · 03-17-2018, 07:09 AM

Quote:

Originally Posted by jeffba

We have a trip planned in April first leg is "as far as I can go". Will post battery voltages at start of trip and when we finally stop.

Sounds like a plan. If I find some time, I'll mount a panel meter somewhere convenient like the drivers side above propane or in near converter. When we make short pit stops, it will be easy to sneak a look at the voltage.

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