Was the residential fridge a mistake?

[twinboat]

Originally Posted by oldbird1965

My Samsung double door residential refrigerator only draws 2 amps. I can hardly believe it myself but according to a Spartan SP-PM 120 power meter left on for 12 hours that's the average.

Yes, 2 amps at 120 volts.

That's 20 amps at 12 volts.

[radar]

Originally Posted by 2Yung2 Quit

I don't think the tow vehicle will typically keep the RV batteries charged unless you specifically wire that way.

Yep. It will. Without problem. All properly wired 7 pin truck plugs are wired this way.

He should also consider throwing a couple of 200 watt solar panels on the roof. Solar is cheap.

Residential refrigerators rule...ammonia fridges drool.

[2Yung2 Quit]

Originally Posted by radar

Yep. It will. Without problem. All properly wired 7 pin truck plugs are wired this way.



He should also consider throwing a couple of 200 watt solar panels on the roof. Solar is cheap.



Residential refrigerators rule...ammonia fridges drool.

So to test this, I would put the meter on the indicated pin and the ground?

[richard5933]

Properly configured with adequate batteries and/or charging capacity, residential units can work with boondocking.

There are other options besides the LP and residential units, like the 12v compressor fridges. Great thing about RVs nowadays is the number of different paths to the same place.

[ascdds]

Originally Posted by mrgrayaz

You sound like you desperately want us to back you up on this (confirmation bias) when actually it's really no big deal....

Actually you are completely and totally wrong. My friend just bought his Solitude, doesn't know much about it or using a website like this for answers. I had actually encouraged him to get a residential fridge since I loved mine so much, however, I didn't know it only came with 2 batteries and no autogen start like my coach. Also didn't know his truck would keep his batteries charged. Neither of us knowing the answers, we were concerned it may have been a mistake. I said I would post the questions here. I am very pleased with the informative and polite responses from the other posters, and the revelation that our worries about his fridge were unfounded. Thanks to all of you who were helpful.

[TRNewsom]

He has a generator so boondocking should be no problem. As said before, monitor batteries. I just don’t think I could go back to rv type. ~ Teresa N.

[radar]

Originally Posted by 2Yung2 Quit

So to test this, I would put the meter on the indicated pin and the ground? Attachment 253210

Yup. That’ll work. Should be there IF THE TRUCK IS ON.

[oldbird1965]

Originally Posted by twinboat

Yes, 2 amps at 120 volts.

That's 20 amps at 12 volts.

Thanks for the info Twinboat! I have four batteries and a 3000 watt invertor so have never had a problem.

[Redapple]

Yep, with 4 batts, 20 amps per hour at 12 volts with a 50% duty cycle you can easily go 10 hours between charges on inverter.

Originally Posted by oldbird1965

Thanks for the info Twinboat! I have four batteries and a 3000 watt invertor so have never had a problem.

[twinboat]

Originally Posted by Redapple

Yep, with 4 batts, 20 amps per hour at 12 volts with a 50% duty cycle you can easily go 10 hours between charges on inverter.

Its not 20 amps per hour. The fridge only runs 1/3 of the time. Its 7 amps per hour or 7 AH.

[richard5933]

Originally Posted by twinboat

Its not 20 amps per hour. The fridge only runs 1/3 of the time. Its 7 amps per hour or 7 AH.

The post stated that 2 amps per hour was the average @ 120v after running the fridge for 12 hours. That is approximately 20 amps @ 12vdc. Since the figure was the average over 12 hours it already incorporates duty cycle.

[Paul R. Haller]

Yes, it will work but your 2 batteries will die after 5 or 6 hours, and don’t count on your pithy 12 gauge charge line to help you recharge your batteries no matter how far you drive. My experience and real world testing shows that even with a 150 amp alternator and standard 12 gauge wires run back to charge the trailer batteries on the road there is too much resistance to adequately charge up batteries in the trailer from the truck. In my truck with a 150 amp upsized alternator and I have 6 golf cart 6 volt batteries in the trailer with a residential fridge that draws about 1.3 amps of 110 AC power. Ohms law dictates the 1.3 amps at 110AC =13 amps out of batteries at 12 volts. Add to that a 20 % efficiency loss of the inverter and undersized charge leads you are talking now 16 amps just to keep up with battery draw from the fridge never mind any extra charging. My testing reveals that to get that transfer of 15 to 20 amps back to the batteries of a fiver reliably is you need to run at least a #6 wire so you can get the resistance of the wire low enough to allow even a modest charge voltage. I run 2 #4 welding wires, 1 being positive directly from the alternator on the truck, the other wire is a good ground on the truck, through a 200 amp rated separate winch connector back directly to the trailer batteries with a 60 amp fuse in between. That’s the only way to get voltage up high enough to charge your batteries and don’t rely on your umbilical contacts to deliver that amperage... they will not in the long haul.

How many of you have actually checked your charge wire size and condition of ground from your tow vehicle to the trailer? My guess is not too many. I was shocked to measure a new truck and trailer to be almost 18 ohms resistance from truck to trailer. Remember also it’s both positive and negative wires. So, in short, the only way to adequately charge your batteries in a fiver, is to upsize your positive and negative feeds back through a reliable, heavy duty, connector with a heavy duty 200 amp relay to separate your two battery banks when the truck is off, and a large fuse to prevent a fire from a short. A measly 12 gauge wire through an umbilical connector and a questionable ground of 12 gauge wire will not do it. Not even close. -Paul R. Haller-

[twinboat]

Amps is an instant measurment of current. What's being draw at that moment.

AH ( amp hours ) is a measurement of amps used over 1 hour.

If you draw 20 amps for 12 hours, that equals 240 AH from your battery @ 12 volts.

If you draw 20 amps 1/3rd of the time, from your battery and nothing the other 2/3s of the time, for 12 hours, that equals 78 AH @ 12 volts.

Originally Posted by richard5933

The post stated that 2 amps per hour was the average @ 120v after running the fridge for 12 hours. That is approximately 20 amps @ 12vdc. Since the figure was the average over 12 hours it already incorporates duty cycle.

[grindstone01]

For our Cameo fifth wheel, none of the 120v outlets run off the inverter. I installed a resident refrig and a 700W pure sine wave inverter next to the existing single RV battery. For travel days, I run a extension cord to the refrig and even on a hot day after a 10 hr drive, we arrive with the refrig cold/on and a full charged RV battery.