TAB 320 Battery when driving/hooked up - ON or OFF?

Last fall, we took a 15-day trip in our 2018 TAB 320, our first trip longer than 3 days.  Of the 6 parks we stopped at, 5 had electrical hookups; the 6th did not. When we arrived at the 6th, and started using lights on battery power only, the lights flickered and we immediately noticed that the battery voltage was quite low (10.5 or so). Surprise! We thought we were being proactive by leaving the battery switch in the “ON” position the entire trip, assuming the battery would be charged by the car while we drove and by the hookup while the trailer was at rest. Obviously not – our bad! Can anyone answer two questions: (1) why did this happen? and (2) how do we avoid this on our next adventure? Thanks for any advice!     


  • pthomas745pthomas745 Member Posts: 1,452
    edited February 13
    Your battery needs to be on while driving for the emergency brakes to work.
    Your car either: does not have a dedicated charging line from the car to the battery.  Or the car does not charge the battery enough while driving.  Or,
    On the last day of the trip, if your fridge was in "battery" or "electric" setting when you pulled away from your campsite it could have easily brought the battery down while you were driving. 

    2017 Outback
    Towed by 2014 Touareg TDi
  • TampakayakerTampakayaker Member Posts: 202
    edited February 13
    I'm not an expert but from some previous posts these may be the cause of your problem.

    How was the 7 pin wired up in your tow vehicle? Was it a factory installed tow package or aftermarket? 
    There is a connection (pin 4) to feed 12 volts from the tv to the trailer. 
    I added my 7 pin connection (no factory wiring), and ran a heavy gauge wire from pin 4 to a kill switch then directly to my battery.  The kill switch is to shut off the drain from the battery to the trailer when stopping (lunch, rest area, etc).  If this was an aftermarket install, the wire gauge may not be heavy enough to charge the trailer battery.  Should be 10 or 12 gauge.

    Alternator may not be heavy enough to charge the extra load of the trailer battery.

    Do you run with the tv headlights on?  Some of the vehicles alternators will put out a higher charge when the headlights are on. In a previous post, someone had found that information in their tv owners manual.

    Corroded connections?

    Was everything turned off in the trailer?

    IS the trailer battery in decent shape/will it hold a charge?

    And if you have electric brakes on the [email protected], the battery switch needs to be on to activate the emergency breakaway brake switch.

    And it helps if you have in your profile, what type of [email protected] and tow vehicle you have to help people giving you answers.
    2006 RAM 1500 4 door, 2016 [email protected] 320 MAX S 
    Tampa FL
  • Denny16Denny16 Member Posts: 1,527
    Yes, you want the battery switch set to on.  I agree with previous post, check your TV wiring and see if pin 7 has enough to charge the TaB.  Also have the battery checked, sounds like it was not getting charged at all, even while hooked up to ext. power.   A good battery should give you several days of led lighting.  Is your fridge a 3-way, I’d so on 12VDC it will quickly draw down your battery. 
    2018 TaB400, Jeep Gladiator truck, Northern California Coast
  • ScottGScottG Moderator Posts: 3,691
    I agree with all of the above particularly if you were running your fridge on DC while underway.
    However, if you were not running your fridge (or otherwise drawing a large load from the battery while on the road) I find this more perplexing. You are correct that your converter should have been charging the battery while you were at the sites with shore power. Even if your vehicle does not have a proper charging line, I would not expect your battery to lose so much charge while you were relocating to your final campsite.
  • MarcelineMarceline Member Posts: 808
    edited February 15
    In addition to everything @Tampakayaker said, I would suggest that you add some kind of battery monitoring capability to your trailer. The gold standard is a Victron monitor ($$$), but it's also possible to monitor the battery (voltage only) with something as cheap as this bluetooth monitor.
    San Francisco Bay Area
    2013 CS-S [email protected]
    Battered but trusty 3.5l V6 Hyundai Santa Fe
  • MiquelCamoMiquelCamo Member Posts: 91
    First of all, you do need to leave the battery on or as mentioned the emergency breakaway brakes will not function.

    You might provide specifics on your tow vehicle but my F150 has factory tow package but is not set up from the factory to recharge the battery. It came with a fuse and circuit breaker in the glove box that had to be installed. Also, as mentioned check that yours is wired.
    Mike and Lisa Campbell
    Springfield, MO
    2016 [email protected] Max S - Sold March 2020

  • Sharon_is_SAMSharon_is_SAM Moderator Posts: 6,076
    @gbc, if you do find that you need to have a charge wire placed, ask for at least 10 gauge wire.  The bigger the better.  It will enhance your ability to charge your TaB battery while towing.  Towing with your frig on 12v may still be an issue, but there are ways to compensate for that.
    Sharon / 2017 [email protected] CSS / 2015 Toyota Sienna Minivan / Westlake, Ohio
  • CalamityJanieCalamityJanie Member Posts: 5
    Newbie here. I'll be looking at some 320s [email protected] this week and next. I hope to buy one. Can someone please tell me what electrical accessories I have to have to hook up my tow vehicle (6-pin flat connection) to the trailer? Is the wiring a 4-pin or a 7-pin, and do I need some kind of adapter? I have looked all over for this basic information and can't find it anywhere. Also, can someone recommend a circuit-tester that will test both the 6-pin and 4-pin/7-pin connections? I want to thoroughly test my tow vehicle before I even go to pick up the trailer! Thanks so much. I know I am clueless.
  • pthomas745pthomas745 Member Posts: 1,452
    edited February 15
    The trailer has a 7 pin connector.
    Here is a tester for a 7 pin. is a great source for all things "towing". On this link there are these sort of adapters:
    And more examples of connectors and adapters.

    Etrailer will answer many of your questions by email (unless one of the local Tab geniuses chimes in!)

    2017 Outback
    Towed by 2014 Touareg TDi
  • CalamityJanieCalamityJanie Member Posts: 5
    pthomas745 thank you for this helpful information! Never heard of that website! 
  • mrericmreric Member Posts: 151
    something is wrong with your charge line.   it should be charging your [email protected] battery,   but more details is needed.   how long after did the battery die?  how old is the battery?  what condition,   have you tested the battery 
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