Towing vehicle battery voltage drops to 10 volts overnight with camper RV plug attached and NOW shore power hookup

[Heckler45]

GOOD morning fellow rv owners. We have had two travel trailers in the past 20 years. This is our FIRST travel trailer with a 12 volt refrigerator/freezer system and a solar panel. I worked as an automotive technician for 32 years so I maintain all of my equipment like you wouldn't believe. We picked up our camper from the rv dealership (Refrigerator cooling issue) on Friday and I just left it parked in the driveway hooked up. I left the 7 pin rv plug attached and DID NOT hook up any shore power. I went to move the truck the next morning and the battery was low, I could tell by the sound it was making and thought "This isn't good." I checked the truck 12 volt battery and had 10 volts. My first thought was, of course the battery...but it's only 3 years old. I charged it overnight and it passed with flying colors. Then, I checked the alternator output....oh yeah, 100 amps and room to spare. Time to move on to a voltage/current draw.........I used my trusty Fluke 77 meter and nope, NO current draw other than the typical parasitic draw. I then remembered that the 7 pin rv vehicle plug has a 12 volt tab.......could the camper be drawing the vehicle battery down a few volts? So, I disconnected the shore power cord and backed up the truck to the camper. I had my wife watch the Fluke meter reading as I re-attached the 7 pin rv cord from the camper. There it is, the current draw increased to 1 amp. Has anyone else had this issue? We never had this issue with our last two campers.

 

[Kevin D Pem]

Did you install a battery isolator in the truck?

What amp capacity are the trailer battery bank.

Did the batteries have the same reading (voltage) in the trailer as the trucks?

As simple as wiring really is. The complications land in the calculations.

Most people expect to much from batteries, and the related charging system.

 

[Heckler45]

I never needed to install a battery isolator in any of my towing vehicles before. I still have my 1994 Chevy Suburban I used for towing the last two campers, never an issue. The camper has only one 12 volt battery now, I am installing two in the near future. I did not check the voltage of the camper battery vs the truck battery. I purchased the 2012 Dodge Ram brand new so I know the entire history of the truck. NEVER had any electrical problems before. One way I guess to really perform a quick diagnosis is to hook up the truck to the camper with the 7 pin rv plug, disconnect the shore power cord and then.....shut off the refrigerator. If the truck battery maintains 12 volts and starts right up, there's the answer. My main concern is has anybody else had this issue with the newer 12 volt refrigerator/freezer design?

Did you install a battery isolator in the truck?

What amp capacity are the trailer battery bank.

Did the batteries have the same reading (voltage) in the trailer as the trucks?

As simple as wiring really is. The complications land in the calculations.

Most people expect to much from batteries, and the related charging system.

Thanks for the response.

 

[Phillbo]

I would never leave mine plugged in to the truck overnight. Not worth killing the TV battery and leaving me stranded in the morning.

 

[Heckler45]

I would never leave mine plugged in to the truck overnight. Not worth killing the TV battery and leaving me stranded in the morning.

Good evening, I agree. But my question is still the same....is there anybody out there with a travel trailer who had experienced this? Thank you for the response.

 

[Kevin D Pem]

I never needed to install a battery isolator in any of my towing vehicles before. I still have my 1994 Chevy Suburban I used for towing the last two campers, never an issue. The camper has only one 12 volt battery now, I am installing two in the near future. I did not check the voltage of the camper battery vs the truck battery. I purchased the 2012 Dodge Ram brand new so I know the entire history of the truck. NEVER had any electrical problems before. One way I guess to really perform a quick diagnosis is to hook up the truck to the camper with the 7 pin rv plug, disconnect the shore power cord and then.....shut off the refrigerator. If the truck battery maintains 12 volts and starts right up, there's the answer. My main concern is has anybody else had this issue with the newer 12 volt refrigerator/freezer design?

Thanks for the response.

Yes and no to your question. I was given a dometic 12 v fridge like that is frequently installed in a conversion van. I tested it. Ran using 45w of power. The insulation was poor enough that it ran most of the time. When loaded it ran less but still a significant amount of the time.

A 28 series battery is roughly 100ah, making 50 ah available 50x12 is 600w. Over night leaving a 45 watt porch light on on the trailer could results in in 500w draw down. At that rate with a 45 watt load 10.5v reading could, and in My experience would be a strong possibility.

I used the light example because I had to draw experience from My earlier experiences, and 12v refrigerators were new and expensive, and honestly I couldn't afford one.

So yes again. The refrigerator load is substantial enough to put an isolator in the truck.

 

[Heckler45]

Yes and no to your question. I was given a dometic 12 v fridge like that is frequently installed in a conversion van. I tested it. Ran using 45w of power. The insulation was poor enough that it ran most of the time. When loaded it ran less but still a significant amount of the time.

A 28 series battery is roughly 100ah, making 50 ah available 50x12 is 600w. Over night leaving a 45 watt porch light on on the trailer could results in in 500w draw down. At that rate with a 45 watt load 10.5v reading could, and in My experience would be a strong possibility.

I used the light example because I had to draw experience from My earlier experiences, and 12v refrigerators were new and expensive, and honestly I couldn't afford one.

So yes again. The refrigerator load is substantial enough to put an isolator in the truck.

Greetings and good evening! Thanks for the reply, that's what I was looking for. On our last two campers, we just turned the refrigerator (120 volt and propane) off while driving. I used to turn on the propane for driving distances at first but the refrigerator would still be cold after several hours of driving with it just turned off. And as far as solar panels go, that battery isn't going to last long with cloudy days at the campground. I will certainly start to research a battery isolator. Thank you for the reply.

 

[d23haynes57]

Bet would be that this travel trailer has limited battery capacity and the solar is a bit of a joke. Consider doing some upgrade work for the entire electrical to fully meet your needs. Battery, inverter-charger, and a proper, controlled charge system from the truck if you need to rely on that.

 

[Old one]

My expedition has the 7 and 4 pin trailer conectors and as said the 7 pin has a 12 V pin in it. However, this goes thru a relay and is only connected when teh ignition switch is in the "run" position and is separately fused at 30 amps.
Possibilities:
1.the trailer draws not have a battery maintainer/charger
2. the 12V power converter usually is a source of 12V to run the RV WHILE the RV is plugged in, and of course is nit plugged into house power while in the yard.
3. being you siad it's new, maybe the factory screwed up the wiring, and something is powered up.
I would also check with the Fluke is the 12 pin in teh 7 pin on the tow vehicle is "live" with the vehicle key off. AND.... 10V means one cell is sulfated, have a load test be done on the battery.
May I suggest going to Bass Pro and getting a 15 amp, single battery "smart" or 3 stage, charger, and have this plugged in when at home. This is what my boat has and I get 10 years out of my batteries.
As said above, read the RV manual carefully.