driving with battery turned off

mjehle9125

Does the car charge the trailer battery even if the battery is in the off position?

Sharon_is_SAM

The car will only charge the battery:
 if you have a charge wire as part of your TV 7 pin and the battery switch is turned to the “on” position
and if your TV electric programming allows for adequate voltage.

Regardless, you should always drive with a charged battery and with the battery switch turned on to power the break-away brakes in the event of a break away.

If you have solar, it will charge the battery continuously, depending on solar availability.

dragonsdofly

@mjehle9125, what @Sharon_is_SAM said 10 X! Never tow with the battery off or without a working battery hooked up. You will endanger yourself, anyone with you, and everyone on the road with you. Be safe. Stay alive and well, travel safely. Happy t@bbing!

Mickerly

I don't know what model or year you have. So, I can't say what you have, but I can describe ours. We have a 2018 CS-S. We have a solar port, but no installed panels.

By using the panel inside to check battery voltage, I have verified the owners manual is correct. The TV will charge the trailer battery with the battery disconnect open (battery off). Turn the battery off. Check the battery voltage with the TV off. Then start the TV. The voltage should increase if the battery is charging. This assumes your TV is wired with a good 12 volt line in the 7 pin plug. Either way, you will know the real answer to your question for your rig.

The solar charge controller and external port attach to the battery side of the disconnect switch too. So, solar panels (if installed) should charge the battery with the switch in any position. If you have an installed panel, it may be difficult to tell if the TV is charging. Throw a blanket over the panel to remove it from the test.

The emergency brake controller should be powered directly from the battery making the battery switch position redundant for safety. I've not verified this, but the maintenance procedure appears it should work this way.

I agree, always travel with a charged battery.

pthomas745

There are some interesting threads on the battery switch and the emergency brake.  Full of pictures and descriptions of the wiring to the battery from the seven pin, and the emergency brake wiring.

https://tab-rv.vanillacommunity.com/discussion/9774/breakaway-brakes-and-battery-disconnect-switch-t-b-320

Mickerly

I tested mine yesterday. I raised one wheel off the ground, spun the wheel and pulled the emergency brake cord. With the battery disconnected, nothing happened. Battery connected, the wheel stopped instantly. On this trailer, the emergency brake needs the battery on.

ScottG

Mickerly said:

...
By using the panel inside to check battery voltage, I have verified the owners manual is correct. The TV will charge the trailer battery with the battery disconnect open (battery off). Turn the battery off. Check the battery voltage with the TV off. Then start the TV. The voltage should increase if the battery is charging. This assumes your TV is wired with a good 12 volt line in the 7 pin plug. Either way, you will know the real answer to your question for your rig.
...

I do not believe this is the case. In my trailer (and in every other T@B I am aware of), the 12VDC+ wires to/from the battery, pigtail, converter, and breakaway brakes all radiate from the same pin in the forward junction box. If the battery is disconnected it will not receive power from the tow vehicle via the pigtail.

However, in the circumstance you describe the tow vehicle will send 12V to the converter, and that higher voltage will be reflected in the inside panel. 

Denny16

With the trailer brake away switch wired to the tow vehicle 7-pin 12VDC hot wire, the trailer brakes will work, with the battery switch on or off (however, the battery will not charge if the switch is off).  The main issue with towing with the battery switch off is if the 7-pin cable came disconnected from the TV in a towing failure event, the brakes will not work once the 7-pin looses its connection.  This is why it is a bad idea to tow with the battery switched off, not to mention the legal issues involved.
cheers

ScottG

I took a slightly different approach when I added my cutoff switch. Mine is inside on the line between the junction box and the converter. This allows me to disconnect everything in the camper (thus eliminating any phantom drain) but still leave the battery permanently connected to the tow vehicle charge line and the emergency breakaway brakes.    

Sharon_is_SAM

We don’t know which TaB the OP owns.  @ScottG - has any 400 owner ever confirmed operation of the break away brakes with the battery switch off?  I think an owner using lithium rigged something to be able to tow with the switch off, but not sure about standard wiring on a 400.  @Verna - you owned a 400 - what do you think?

@Denny16 - are you saying the 400 break away brakes operates just like the 320 - that is, you must keep the switch on?  The brakes will work regardless of the battery switch, the question is if the brake away brakes will work with the switch off.

ScottG

While I have never had the opportunity to dissect a 400 myself, the limited accounts I am aware of suggest the 400 is wired the same as the 320.

It wouldn't be particularly difficult for an owner to rewire the breakaway switch so that it is always powered regardless of the battery cutoff, but I don't believe any were shipped that way from the factory.

I agree with @Denny16's assessment. The confusion may arise as to whether we are talking about the regular operating brakes or the emergency breakaway brakes. The operating brakes are always controlled and powered by the tow vehicle--just like the external lights, these have their own terminals in the forward junction box and are not connected to the battery. The operating brakes would be irrelevant in the event of a complete trailer separation.

In contrast, the breakaway brake switch is connected to both the tow vehicle and the battery. The breakaway brakes become most important in the event of a separation, so they should always remain connected to the trailer battery.

Note here that while I talk about the operating brakes and breakaway brakes as separate entities, the brake mechanisms themselves are the same in both cases. What differs is the wiring route by which those brakes are engaged and powered.

Regardless, we are getting adrift of the OP's question, which was about whether or not the tow vehicle would charge the battery if the battery switch is off. My understanding is it will not, regardless of the model or year of T@B.  

Verna

There are two wires on my positive side of the battery. One goes to the battery junction and one goes to the solar controller (I may have two solar controller wires as I have two solar controllers, but I cannot check right now). This means that only the solar controllers bypass the wiring junction on the tongue, and that means no power goes anywhere (except solar panels feeding the battery) if the battery switch is off. To me that means no emergency bakes if the power switch is off. 

@Sharon_is_SAM, I’m one of those who listens to both sides and makes my choice. I always double check to make sure my battery switch is ON, as that gives me the most probability of having power to both the emergency brake and the normal brakes. I actually see no advantage to turning the power OFF while driving as I also want my tow vehicle to charge the T@B’s batteries while towing. If I don’t want the fridge to use power while driving, I turn just the fridge off. 

Yes, I have traced the wiring to the switch to be certain it was wired correctly — OFF means no battery power to the T@B, ON means there is power to theT@B. 

ScottG

Yep, the solar controller (if equipped) appears to be the only thing wired directly to the battery (i.e., not passing through the cutoff).

It could be argued that this same arrangement should apply to the emergency breakaway brakes as well. 

Denny16

“ @Denny16 - are you saying the 400 break away brakes operates just like the 320 - that is, you must keep the switch on?  The brakes will work regardless of the battery switch, the question is if the brake away brakes will work with the switch off.”

Yes, @Sharon_is_SAM, the battery switch muse be on with the TaB 400 (at least on ours) before the breakaway switch will work correctly and apply power to the brakes.  This was tested by our trailer service guy, he tried the brakes both ways, and recommended adding a label to the battery switch location to this effect, “Warning Battery switch must be on before towing”.
cheers

Sharon_is_SAM

Thank you @Denny.  We now have confirmed that both the 320 and 400 require the battery switch to be turned on for the break away brakes to work upon a complete separation.  I think a label is a good idea!

Mickerly

NuCamp appears to have added a note to the Owners Manual in the 2021 trailers stating the battery must be connected/on during towing to ensure operation of the emergency brakes. It is; however, buried in text rather than a highlighted paragraph. Manuals for the older trailers don't say anything. A label is a good idea.