When plugged in to shore power, do you need the battery cutoff turned on?

Lawyerboy

Good day folks.  So, when I get to the campsite, we plug in to shore power.  That said, we have the battery cutoff on, since we would have kept it on while driving, to feed the fridge.  BUT, when at the campsite, and plugged into shore power, should the battery cutoff be in the off position, since we would no longer require the battery until we tie back in to the tow vehicle?  Sorry if this is a basic question, but appreciate insight.

MuttonChops

Short answer:  Keep T@B Battery Switch in the On position.

With Battery Switch On, T@B WFCO Power Center will recharge the battery drained while driving.  Tow Vehicle +12V 7-pin connector in most cases can not provide enough power to keep the battery charged and the Fridge running.  In fact if your T@B has a 3-way Fridge (Shore power, Battery, Propane) then suggest you do some research on the forum as to risks / how best to operate a 3-way Fridge on 12VDC power.

Primary reason to have the Battery Switch On while driving is to have power available to the T@B electric brakes if the tow hitch failed.

Lawyerboy

I always have the battery on while driving for that 7-pin, to keep the fridge on, etc.  My question is when I get to the campsite, do I need the battery on when plugging into shore power?

pthomas745

Think about where the battery cut off switch is.  On a 320, the switch is between the trailer and the battery.   If you turn it off, the trailer cannot draw power from the battery.  It has become "separated" electrically from everything in the trailer.

Plug in the trailer to shore power with the switch off: the WFCO has no access electrically to the battery, since the "cutoff" switch prevents power going to the battery.

(I would suppose the 400 has the same setup for the switch.)

falcon1970

You don't really "need" the battery cutoff switch in the on position when connected to shore power but if the switch is OFF you will not be charging then battery from the shore power connection.  If it is in the ON position you will be topping off the battery from shore power.  As mentioned above, not all tow vehicles can manage to charge the battery while driving.

Also as mentioned above, turn the battery cutoff switch to OFF and ensure all other electrical devices are in the OFF position before you connect to shore power.  Only then turn the battery switch ON as well as any other electrical devices (fridge, Alde, AC, etc) that you want to use.  This helps prevent stray voltages or surges from damaging electrical equipment.  The Alde is particularly susceptible.

As a final note, I strongly recommend you connect an EMS device inline with your power cord.  Campgrounds have been known to have less-than-clean power supplies.

ScottG

I often leave my fully charged battery disconnected when I am in a campsite with shore power. To answer your specific question, there is no need to disconnect it, but it won't hurt anything if you do.

Just remember to turn it back on when you depart. You don't necessarily need it to run your fridge, but--as noted by others--it is an essential part of the breakaway braking system.

MuttonChops

Lawyerboy said:

. . . My question is when I get to the campsite, do I need the battery on when plugging into shore power?

Sorry, my short answer was not as clearly written as it could have been

MuttonChops said:

Short answer:  Keep T@B Battery Switch in the On position when connected to Shore Power.

Lawyerboy

Thank you all.  Typically, I keep it on, until I get home, and then shut off the cutoff switch and then I put a battery tender jr on the battery to top it off again.  Was one of those questions I pondered as to need when plugged into shore power.  If the shore power tops it off, I guess on it can be, or shall be.  TY all.  Now if the snowbirds would leave Florida so I can find a two day reservation somewhere, life would be grand.

N7SHG_Ham

On 100% of the time unless storing for indefinite period. Mine has never been off in two years, solar on roof and my storage has a 30a service. It is only turned off to prevent discharge from phantom loads if the battery does not have a way to charge when stored.

Tundra57

Battery also acts as a filter to smooth the output of the charger. Some sensitive electronic equipment may prefer it. Also you may get more noise on your sound system at low volumes. Unlikely to cause any damage if you leave it off. You wont be able to run the inverter without, but on shore power that wont be needed.

ScottG

@Tundra57, I assume you mean the output of the converter, since the charger presumably wouldn't be operating with the battery disconnected.

I remember reading something here years ago the bit about leaving the battery connected to smooth the output of the converter while on shore power. I've even repeated it a couple times. It makes theoretical sense, but to the degree that fluctuating converter output is an actual problem is unclear. If you are aware of any outside references on the topic I'd be interested in seeing them.

AirBoss

No need to deactivate  the battery switch. Does no harm when your connected to shorepower and its one less thing to consider among the dozens of other things when getting underway. 

Activating that switch is a must before you get underway and can easily be overlooked due to its location. 

In general, it's only deactivated when in storage. Towing, boondocking, full hook-ups, etc. I leave mine on. 

Mouseketab

When I had a television that was 12V, if the battery was off when connected to shore power, I had a fuzzy, wavy picture. As soon as I turned the battery on, the picture cleared up. So the battery does help to clean up the power from the converter.

ScottG

Mouseketab said:

When I had a television that was 12V, if the battery was off when connected to shore power, I had a fuzzy, wavy picture. As soon as I turned the battery on, the picture cleared up. So the battery does help to clean up the power from the converter.

That's interesting--I wonder what that was about, electronically speaking. TV is long gone so I can't check it out. I wonder if the Alde and fridge electronics benefit from this smoothing effect.

gulfarea

Your battery acts like a capacitor and does help keep voltage very stable. Art Ham radio KD4MLK Art