12v/battery/inverter/residential refrigerator

[lesptr]

We did the Flying J overnight parking for a little sleep last weekend on the way to Myrtle Beach. We were parked for the overnight for no more than 7 hours total. Approximately 5 hours into the stay, I woke to visit the the little boys room and heard a barely perceptible beep. As I came around the corner, I heard the beep again and noticed the light on the propane detector was flashing red and that the temperature screen on the refrigerator was illuminated. The only gauge I have to monitor the batteries (at this time) is on the master panel. The batts were showing 1/3. This was our first attempt at dry camping and was a dismal failure. I really thought the batts would last through the night. Lights were used for no more than 20 minutes before bed and are LED.


Ok, now the details.
Coachmen Chaparral 336TSIK purchased in September 2016

2, 12 volt Interstate Batteries. (Batts are believed to be new at time of purchase)
[ATTACH]

Hisense Residential fridge.
(Forgot to take a pic of the spec page of the manual. Will do so if the folks think it is necessary)

Inverter
[ATTACH]

5r is plugged in to 50a service 24/7. All battery tending is done by converter which is WFCO. Not sure of the model.

Propane detector manual says light will flash red during the first 3 minutes after receiving power.

I'm sure there are different ways of correcting this.
2, six volt in series?
Better 12v batteries?
And others I'm sure.

Please keep in mind that I fly airplanes, am military trained i.e. Prefer one line bullet statements, and I'm getting old.
So DUMB IT DOWN FOR ME!


Fire away.

Thanks
L

[CHICKDOE]

when we first got out trailer we tried a night with the residential refrigerator powered by the inverter from 2 12 batteries. they were so dead in the morning that they could not even start the generator. I have learned a great deal since then.


here is the unknown as I see it. what was the state of the batteries prior to your stop. you must have been travelling all day, presumably with the inverter on to keep the refrigerator running. this may have depleted your batteries so that they were not full for the night stop.

[lesptr]

We had been traveling for approximately 5 hours before stopping and the the panel said they were "full".

[325BH]

Without arguing which battery setup is best, I am with the post above. What was running off of your batteries prior to the last charge? This includes all drive time and sleep time since you were last plugged in to shore power.

[VinceU]

Realize a res fridge will use 7 amps approx, lots of usage if trailer is hot underway. The 7 amps is inverted to 70 amps of D.C. Pulling on those two batteries rated maybe 95 amps when new. Do the math it's easy to see even with a 40% duty they probably will not last overnight on a good day.
My system uses 6 deep cycle AGM AND THE FRIDGE LASTS 2 days easily.
You should convert to 4 true deep cycle batteries, you'll be happy you did.
Dealers don't tell customers about the very heavy load 117 volt reefers place on the batteries.

[JCDMeyer]

Originally Posted by VinceU

Realize a res fridge will use 7 amps approx, lots of usage if trailer is hot underway. The 7 amps is inverted to 70 amps of D.C. Pulling on those two batteries rated maybe 95 amps when new. Do the math it's easy to see even with a 40% duty they probably will not last overnight on a good day.
My system uses 6 deep cycle AGM AND THE FRIDGE LASTS 2 days easily.
You should convert to 4 true deep cycle batteries, you'll be happy you did.
Dealers don't tell customers about the very heavy load 117 volt reefers place on the batteries.

117 volts?

[lesptr]

We had been driving for about 5 hours which means it was off shore power for about 5 hours. The inverter was switched on when the power cord was pulled which is the last thing we do before leaving the house. 20 minutes worth lighting before going to bed. We did not extend any slides, so it was just bathroom and bedroom lights, water pump and whatever else that is drawing power in the background without being noticed. Shouldn't the truck keep the battery mostly topped off while towing or can the refrigerator pull more power than the truck is capable of providing?

[Flybob]

With the standard wire gauge in the Aux side of the TV line you will loose enough voltage to do little more than keep the batteries charged without the fridge drawing power. In addition, if this is the first time you have towed with this TV it is very possible the Aux line is not connected. Most new TV come with the aux line run but the fuse and relay ( if your TV uses a relay) is many times supplied in a bag in the glove box. If you want to run the fridge while traveling to a boondock location, you will need a to run a heavier gauge wire from the fuse block to the Bargman connector.

[VinceU]

Originally Posted by lesptr

We had been driving for about 5 hours which means it was off shore power for about 5 hours. The inverter was switched on when the power cord was pulled which is the last thing we do before leaving the house. 20 minutes worth lighting before going to bed. We did not extend any slides, so it was just bathroom and bedroom lights, water pump and whatever else that is drawing power in the background without being noticed. Shouldn't the truck keep the battery mostly topped off while towing or can the refrigerator pull more power than the truck is capable of providing?

Yes it should while underway. Even still not too many truck alternators can supply 70+ amps to the trailer. Besides the charge lead is probably only rated 20 amps. You must design battery capacity to sustain your installation. I also just noted the battery info label rated cold cranking amps and starting amp capacity i.e.: these are dual purpose batteries with a greatly reduced life as compared to true deep cycle unit.

[JLeising]

Turn off the fridge and inverter while overnighting without hookups. If you don't open it, the fridge should stay cold enough to overnight.

[lesptr]

Originally Posted by JLeising

Turn off the fridge and inverter while overnighting without hookups. If you don't open it, the fridge should stay cold enough to overnight.

I may do that. Thanks.

[lesptr]

Originally Posted by VinceU

Yes it should while underway. Even still not too many truck alternators can supply 70+ amps to the trailer. Besides the charge lead is probably only rated 20 amps. You must design battery capacity to sustain your installation. I also just noted the battery info label rated cold cranking amps and starting amp capacity i.e.: these are dual purpose batteries with a greatly reduced life as compared to true deep cycle unit.

I was surprised and a bit peeved when I saw these batteries were not up to the task. I specifically asked for 24 hours worth of refrigerator on battery only. Apparently the dealer said here's one more craptastic duel purpose battery. Now be on your way.

[lesptr]

Does anyone recommend 2 6volt batteries? Will I get an overnight out of two 6v?

[lesptr]

We have been driving for the last 8 hours with a few stope for fuel and food. The panel says the batteries are fully charged. And I did not find a baggy in the glove compartment containing fueses, so I'm guessing my 2015 F350 is charging (or attempting to charge) while I drive. Yes? No?

[ScottBrownstein]

If you mean that your LED indicator has all lit, that means that it is being charged, not that it is full. So, yes, your TV is trying to charge your batteries.

[325BH]

I have a 2016 F250, however I haven't investigated whether the +12v conductor is energized or not.

Going with true deep cycle batteries will help your situation. I have and recommend 6v golf cart batteries combined with a top-notch converter like Progressive Dynamics. (With you having an Inverter, I don't know if it is also a converter or if that is separate in your setup.)

However, having said all that, I'm still not sure the main cause of your battery drain. Was it because overnight was too much or was it because you had your residential fridge running all day while driving? You needs may require more than two batteries... I don't know.

[HONDAMAN174]

Three things: stop at auto parts store and get a 7 way plug indicator. I use it every time I pull to make sure. I have 12v. But as another had said, pulling 70ah will deplete those units quickly. And your ruck will only charge 15amps max

2- there is a 5 digit number melted into the top of your battery. Google that code with interstate date code to find born on date. But imo, those are older batteries cause I just dumped two of those part numbers and had way more capacity.

3- 2 6v units will give you about 50% more useable ah but would be better with 4.

[pgandw]

Before we can give sound advice, we need to know what your residential fridge really draws. Being a 120V appliance, there is a plate near where the cord goes into the unit that says how many watts and/or amps the fridge draws. If you know watts (say 160), divide by 110, then multiply by 10 to get your amps at 12V. If you know amps (say 1.35), just multiply by 10 to get amps at 12V. If my guess at 160 watts is correct - could be a lot more, I assumed a dorm-sized fridge - you are using 14.5AH, round up to 15AH for losses, for EVERY hour your fridge runs.

Two Group 24 Interstate batteries are 80AH each. To keep them above 50% charge (which probably will give you 200 charge/discharge cycles of battery life), you can use 80AH. That gives you 5 hours of run time for the fridge before the batteries are at 50%, with only 5AH available for everything else. If you go below 50% charge on your batteries, the number of charge/discharge cycles drops off rapidly.

To find out how your batteries are doing while towing, measure the voltage at the camper batteries with the fridge running AND the tow vehicle hooked up and running. Turn on the tow vehicle and camper running lights, too. If the voltage at the camper batteries is 13.2 are greater, the tow vehicle will keep the batteries charged. It probably won't add much charge, but will maintain. If the voltage is less than 13.2, the tow vehicle wiring can't keep up with the load.

My little A-frame fridge has a 160 watt DC coil - and it's continuous run with no thermostatic control. So when I am towing I am drawing about 13.5 amps (160/12). I do have 13.2 - 13.6 volts to the camper batteries with running lights and fridge on, and minivan running. So my tow vehicle wiring is good. I did replace my tail light bulbs with LED bulbs to reduce the load by a couple of amps. But the big thing - I absolutely must shut the fridge off of 12V before I disconnect the tow vehicle or set up camp. If I don't shut it off, I will significantly drain my batteries before I even get started camping.

Looking at the numbers, dry camping/boondocking with a residential fridge requires a generator or significant solar power (300 watts or better), and a good-sized battery bank (typically 4 batteries).

Fred W
2014 Rockwood A122 A-frame
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time

[lesptr]

Originally Posted by ScottBrownstein

If you mean that your LED indicator has all lit, that means that it is being charged, not that it is full. So, yes, your TV is trying to charge your batteries.

I did not know that, thank you.

[lesptr]

Originally Posted by pgandw

Before we can give sound advice, we need to know what your residential fridge really draws. Being a 120V appliance, there is a plate near where the cord goes into the unit that says how many watts and/or amps the fridge draws. If you know watts (say 160), divide by 110, then multiply by 10 to get your amps at 12V. If you know amps (say 1.35), just multiply by 10 to get amps at 12V. If my guess at 160 watts is correct - could be a lot more, I assumed a dorm-sized fridge - you are using 14.5AH, round up to 15AH for losses, for EVERY hour your fridge runs.

Two Group 24 Interstate batteries are 80AH each. To keep them above 50% charge (which probably will give you 200 charge/discharge cycles of battery life), you can use 80AH. That gives you 5 hours of run time for the fridge before the batteries are at 50%, with only 5AH available for everything else. If you go below 50% charge on your batteries, the number of charge/discharge cycles drops off rapidly.

To find out how your batteries are doing while towing, measure the voltage at the camper batteries with the fridge running AND the tow vehicle hooked up and running. Turn on the tow vehicle and camper running lights, too. If the voltage at the camper batteries is 13.2 are greater, the tow vehicle will keep the batteries charged. It probably won't add much charge, but will maintain. If the voltage is less than 13.2, the tow vehicle wiring can't keep up with the load.

My little A-frame fridge has a 160 watt DC coil - and it's continuous run with no thermostatic control. So when I am towing I am drawing about 13.5 amps (160/12). I do have 13.2 - 13.6 volts to the camper batteries with running lights and fridge on, and minivan running. So my tow vehicle wiring is good. I did replace my tail light bulbs with LED bulbs to reduce the load by a couple of amps. But the big thing - I absolutely must shut the fridge off of 12V before I disconnect the tow vehicle or set up camp. If I don't shut it off, I will significantly drain my batteries before I even get started camping.

Looking at the numbers, dry camping/boondocking with a residential fridge requires a generator or significant solar power (300 watts or better), and a good-sized battery bank (typically 4 batteries).

Fred W
2014 Rockwood A122 A-frame
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time

Very good info. Thank you. We just arrived home and tomorrow is my get ready to go back to work day. I will work ok this when I get back in town next week.
Thanks again.
Les