Do you disconnect the electrical plug from your car/truck when stopping for an hour or so to shop?

KAR · May 2020

HI, We're about to go on our first trip and was told by a person that they disconnect the electrical plug from their car when they stop at Target or the grocery store if they plan to stay for more than an hour,,,,when they are towing their T@B. We hadn't thought it would be an issue so hadn't thought about it. Thoughts? Experiences? Thanks, K

Sharon_is_SAM · May 2020

Some tow vehicles have an isolation relay that prevents the TaB battery from draining the TV battery. What TV do you have?

Tampakayaker · May 2020

I put a kill switch on the line from the TV battery to the plug.

Mouseketab · May 2020

I do not, but I have an isolation relay that stops the connection from the truck to the T@B when the ignition is off. How to check. Turn off your T@B battery, plug in your 7-way. Crank your vehicle. Turn on a light in the T@B. If the light comes on, you have a charge line from your vehicle. Turn off your vehicle and remove the key. If the light goes out, you have an isolation relay, so no need to unplug. If the light stays on, you do NOT have an isolation relay, and you will need to unplug when stopped.

ontheroad · June 2020

We do because sometimes the hour becomes a little longer...🙂...make sure when you plug in again you do the checking of the lights..we also use this time to do a walk around the trailer.

Marceline · June 2020

If you have a clamshell (2way fridge) you probably don't need to worry about it. If you have a 3way fridge you may need to unplug.

jkjenn · June 2020

I usually do if I am going to be stopped for over 15 minutes.

KAR · June 2020

THANKS to all! No TV. We have a 3 way refrig. I'll do the test to see if we have the isolation relay but I don't think we have one. Appreciate your fast responses! Safe travels! K

Sharon_is_SAM · June 2020

@KAR - TV in this case refers to Tow Vehicle😆

ScottG · June 2020

Is it TV or T/V? AC or A/C?

A few years back there was a lively discussion about the "correct" use and meaning of various camper and camping related terms and abbreviations. :-)

ScottG · June 2020

My tow vehicle has an isolation relay, so I don't unplug when I stop for any length of time. However, if I am running the three-way fridge on DC (direct current) I do turn the fridge off to avoid draining the camper battery while the tow vehicle is not running.

KAR · June 2020

THANKS! Our TV (tow vehicle) is a RAV 4.
This is like learning medical terminology and all our abbreviations! HAHA!
Thanks.
K

GatorEgg · June 2020

No we don’t unless we’re running our refrigerator on battery. Then we shut it off. Sometimes the lady’s momentary stop turns into a marathon.

KAR · June 2020

Thanks. Ours will be more like our quick photo op turns into something longer! I'm not much of a shopper!

YanniLazarus · June 2020

KAR said:

THANKS! Our TV (tow vehicle) is a RAV 4.
This is like learning medical terminology and all our abbreviations! HAHA!
Thanks.
K
we just picked up a used 2018 rav4 adventure and pick up a 2020 tab320 on Thursday. You happy with that combo? And I thought spell check made rv into tv!!!

ChanW · June 2020

We installed an isolation relay when we bought our Tab. It works well. Not too difficult to install if you have electrical savvy.

As noted by others, neither unplugging the 7pin, nor an isolation relay, will save your Tab battery, if you leave your 3-way fridge going on 12V for any period of time (been there, done that!)...

We used this one (West Marine carries it):

KAR · June 2020

Thanks:) K

nhmike · June 2020

I'm blissfully ignorant on this one. we do have the cs-s with a 2-way fridge and have never thought about disconnecting the electrical plug when stopping at the store etc. never had an issue. we do disconnect when our journey is done for the day.

Sharon_is_SAM · June 2020

@nhmike, the CS 2 way frig only draws a max of 4-5 amps compared to 11 amps by the 3 way In the S model. Too many S owners have drawn down their battery while on DC.

rcarlson1957 · June 2020

A little confused here. I'm hearing two things. I was planning on putting a battery isolation solenoid between my battery and the 30 amp auto reset breaker on the 12v feed going to my trailer (it also powers my CURT Echo Wireless Brake Controller) so I don't have to unplug my trailer if I'm doing an extended stop and risk not having enough battery to start my TV. But some are saying on here that if you leave your refrig on 12v the output from most new SUV alternators (my Mazda is 100amp (not big) isn't strong enough to pass thru to the house battery and keep it charged so it will just run down you house battery on a long trip if the frig 12v is on. So if that is the case, why would you have it on 12v when driving and why would you need a battery isolation solenoid. I thought I understood it now am a little lost.

Bayliss · June 2020

@rcarlson1957, it can be a bit confusing.

1. You MUST have the battery switch "ON" while towing, because if the trailer should suddenly become detached from your tow vehicle, the only power to the emergency brakes will be your trailer battery. The emergency breakaway cable on the trailer is designed to activate the emergency brakes on the trailer in that situation. When the plunger is forcibly pulled out of the switch, that creates an electrical connection (via the trailer battery) to the trailer brakes, locking them up so the trailer will stop moving forward.

2. If you are operating your refrigerator on the trailer battery while towing, and you stop for more than a brief period of time, the refrigerator will continue running and will quickly deplete your trailer battery. At least that is how it works with the three-way refrigerator. I can't speak to the the newer two-way version, but as @Sharon_is_SAM has described, it draws less power from the trailer battery.

3. The purpose of the relay switch on the tow vehicle is to prevent the tow vehicle battery from sending power to your trailer when the tow vehicle ignition switch is turned off.

Hope that helps.

ChanW · June 2020

Good question!

I initially believed that our Tacoma (w/o any 'tow package') would output enough power to keep the 3-way fridge going. So I ran with the fridge's 12v mode on.

And I figured, for that "rare" case (sure, rare) when we'd forget to shut off the fridge at a lunch stop or whatever, I'd install an isolater, to at least save the TV battery.

It turns out however, after much trial and error, and then finally with confirmation from the Victron Battery Monitor, the Tacoma standard alternator only does a short initial high amperage charge, and then settles back to what it thinks must be what the system needs. ie: low current charging.

It probably doesn't help that due to the voltage drop between the front battery and the Tab battery, the alternator reads the voltage of the TV battery, and drops the charge rate back, when the Tab battery is still not up to level yet.

At any rate, we don't depend on the 12V mode for the 3-way fridge any more at all, though I'm still willing to experiment with solar charging while we drive.

qhumberd · June 2020

Bayliss said:

@rcarlson1957, it can be a bit confusing.

1. You MUST have the battery switch "ON" while towing, because if the trailer should suddenly become detached from your tow vehicle, the only power to the emergency brakes will be your trailer battery. The emergency breakaway cable on the trailer is designed to activate the emergency brakes on the trailer in that situation. When the plunger is forcibly pulled out of the switch, that creates an electrical connection (via the trailer battery) to the trailer brakes, locking them up so the trailer will stop moving forward.

2. If you are operating your refrigerator on the trailer battery while towing, and you stop for more than a brief period of time, the refrigerator will continue running and will quickly deplete your trailer battery. At least that is how it works with the three-way refrigerator. I can't speak to the the newer two-way version, but as @Sharon_is_SAM has described, it draws less power from the trailer battery.

3. The purpose of the relay switch on the tow vehicle is to prevent the tow vehicle battery from sending power to your trailer when the tow vehicle ignition switch is turned off.

Hope that helps.

This has got me confused from a safety perspective so I want to confirm that the trailer brakes are wired thru the battery disconnect? It seems that a lot of folks could forget to turn on their battery when towing if they leave home with a fully charged battery and are going where hookups are available. My assumption was that the brakes would run just thru the trailer disconnect pin. Is that right or wrong?

Also on the 2 way frig the Unofficial nüCamp T@B400 Resource Guide I got from this forum lists the amp draw of the 2 way at 5.15 amps so a brief stop of even 2 hours would not deplete the trailer or the TV battery. And that is assuming it would run all the time, which it does not when already cooled down.

Thanks all

Sharon_is_SAM · June 2020

Correct. In the event of a complete separation of TaB from TV, the break-away brake switch gets it’s power From the TaB battery, so you must always tow with the battery switch turned “on”. And, make sure your battery is charged enough to be able to deploy the brakes in this situation. While towing, I believe the charge wire supplies brake power to the TaB via the 7 pin.

The 400 2 way frig on DC is far more efficient than the 320 S 3 way on DC. You won’t need to worry with your large 400 battery capacity and efficient frig.

rcarlson1957 · June 2020

So to make sure I understand it all. So the whole purpose of a battery isolation solenoid in the TV is to prevent the TV battery from sending power to the TT is the TT battery gets too low when TV is not running? Also, if you have a 3 way frig and you run it on 12v while going down the road it will eventually discharge your TT battery and the TV alternator doesn't provide enough charge (if it's newer and has a small or smart alternator) on the 12V feed through the 7 pin connector to keep the TT battery topped off when driving. So in my case, I should not run the frig on 12v ever? Just get it cool on shore power before I leave then turn it off and load it with frozen water bottles and when get to site power it from shore power or when boondocking power via LP gas or via shore power using a small generator. Sounds like 12v function is a complete waste on the 3 way then. Or am I missing something?

Sharon_is_SAM · June 2020

If the TaB battery becomes depleted due to the DC frig mode, the system will draw down the TV battery. The solenoid relay prevents current moving from the TV battery.

You got it right. Many folks choose to run the frig on LP while towing or they pre chill the frig, keep frozen bottles inside, and turn off the DC every couple hours while towing.

Some owners use a DC to DC charger while towing. Another owner set up an inverter to power the frig via ac while towing.

KAR · June 2020

It's amazing what people come up with! Creative group!

donmontalvo · November 2024

Sharon_is_SAM said:

@KAR - TV in this case refers to Tow Vehicle😆

Thank you…acronyms can derail a conversation.

donmontalvo · November 2024

Sharon_is_SAM said:

If the TaB battery becomes depleted due to the DC frig mode, the system will draw down the TV battery. The solenoid relay prevents current moving from the TV battery.

You got it right. Many folks choose to run the frig on LP while towing or they pre chill the frig, keep frozen bottles inside, and turn off the DC every couple hours while towing.

Some owners use a DC to DC charger while towing. Another owner set up an inverter to power the frig via ac while towing.

LP?

ckjs · November 2024

donmontalvo said:

Sharon_is_SAM said:

... Many folks choose to run the frig on LP ...

LP?

Liquid Propane

ScottG · November 2024

You may find this old discussion useful (or not...).

I personally prefer T/V--or better yet the actual words TOW VEHICLE--when referring to the, um, tow vehicle.

Do you disconnect the electrical plug from your car/truck when stopping for an hour or so to shop?

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