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question about battery

Npdchief07
Explorer
Explorer
Can someone explain to me what the battery actually does on an rv? I just got a new 2020 Transcend. It has a battery disconnect switch. When I park in our drive, I turn the disconnect to on. It has been parked for a week and battery is dead (the slide won't go out, lights don't come on etc.). I have plugged it back in to an outlet and it appears to be charging again.

What exactly does that battery power? If it has a disconnect switch in the rv, should I still disconnect the cables?

I don't understand electrical. I don't know a volt from an amp.
18 REPLIES 18

kellem
Explorer
Explorer
The simplest thing to do is leave the the trailer plugged in year around.
I'm 10 years in on latest trailer and not once have used the disconnect.

Drained batteries have little life expectancy.

whiteeye42
Explorer
Explorer
not to be mean but if you don't understand how the trailer operates then it is time to either take it to the dealer and have them explain everything or get rid of the trailer
Me,Wife two boys and two dogs
2008 Dodge Ram Quad Cab 4x4 DRW 6.7 cummins
2008 Jayco Eagle 341 RLQS 37' with B&W turnover ball & companion hitch
using rotochoks
add state map

happy2rv
Explorer
Explorer
Npdchief07 wrote:
So when not in use I should have the battery disconnect turned to off?


This seems like an easy question to answer, but its not. The best answer I can give is it depends on a number of factors.

Battery disconnects are wired differently in different coaches and depending on whether they were installed by a manufacturer, dealer, or a previous owner in the case of a used coach. It may also depend on where the disconnect is installed. Many, perhaps most, are true battery disconnects in the sense that when you switch them off, they completely disconnect the battery from the coach. However, some manufacturers and owners bypass the disconnect for some circuits.

Going back to your original question,
What does the battery power?
Some things may seem obvious. Lights, electric tongue and stabilizing jacks if so equipped, slide motor(s), awning motor, etc are all "obviously" battery powered. I expect what you really meant was I'm not using these obvious things while its sitting in the driveway, assuming you didn't leave a light on by accident. So why is the battery dead? There are some not so obvious things, especially if you're new to RVing. Every RV is required to have a gas detector installed and this runs anytime the battery is connected. Some have battery powered CO detectors and/or smoke detectors. Traditional RV refrigerators will draw power from the battery if they are set to gas or DC. Newer residential refrigerators have power inverters that convert battery power to AC to run the refrigerator. These will drain multiple fully charged batteries in a matter of hours if left on. Some RVs have smaller inverters for powering a TV or other appliance but these aren't usually installed from the factory. The furnace may draw power if the thermostat is set to furnace. Even if it doesn't need to run, the control board my use power. The thermostat itself on most newer RVs is powered by the battery. Some have clocks powered by the battery.

So, assuming that your disconnect switch disconnects all of these loads, switching it off will prevent those loads from discharging your battery quickly. If just your gas detector is left on your battery or batteries may last a couple of weeks to a couple of months with them switched on. The bad news is that lead acid batteries (the type usually installed in travel trailers from dealer) discharge themselves if left unattended even if they are completely disconnected. At moderate temperatures, lead acid batteries self discharge at a rate of around 5% per month and the self discharge rate increase with higher temperatures.

Your RV has a power converter that charges the batteries when you plug into AC power as well as providing power to the things your battery powers when you're not hooked up to AC. Unfortunately, these converters are notoriously poorly suited to long term battery maintenance. They tend to overcharge batteries when left hooked up indefinitely.

The "best" storage method depends on how long you're going to store the battery. My preferred method of storage is to disconnect the battery from the RV and connect it to a charger that is specifically designed for storage maintenance. I currently have a battery tender brand charger with a quick connect cable that stays attached to my batteries and I just plug the charger in when I put the RV in storage. If you are going to be using the RV regularly, and only storing for a few weeks between uses, then you would probably be fine just switching the disconnect off or leaving the battery disconnect on and plugging the RV into AC.

There are many reasons not to just plug the RV into AC for long term storage. One of the biggest as stated above, is that the converter/charges on almost all RVs will overcharge the batteries, boiling off electrolyte and shortening the batteries life. Another reason to avoid long term unattended AC hookup is the potential for power surge / brownout damage. Unless you have a dedicated RV hookup with a good surge suppressor (which I would recommend), even if you aren't using the appliances in the RV they are subject to power quality issues and lightning damage. There's also no need to run the refrigerator or any other appliances for months at a time when you aren't using them. Finally, many (most) newer RVs have an AC heating element in the water heater. While this should be turned off when not in use, if you forget and leave it on while not connected to a water source any water in the heater, assuming you didn't drain it, will eventually boil and/or evaporate and the heating element will burn out or worse.
2018 Forrest River Salem Hemisphere 282RK - 2017 RAM 1500 TV

Previous RVs and TOADS
2004 Fleetwood Bounder 32W on WH W20
2000 Four Winds 5000 21RB
1986 27' Allegro
TOADS
2005 Ford Ranger XLT 2WD
2004 Suzuki Aerio
1988 Chevrolet Sprint

beemerphile1
Explorer
Explorer
2oldman wrote:
Npdchief07 wrote:
So when not in use I should have the battery disconnect turned to off?
They should call it a battery connect. That way it makes more sense to be "off."


Switches make more sense when referred to as open or closed. A switch cannot be on or off, but a light can be on when a switch is closed and the light is off when the switch is open. Peeve of mine.
Build a life you don't need a vacation from.

2016 Silverado 3500HD DRW D/A 4x4
2018 Keystone Cougar 26RBS
2006 Weekend Warrior FK1900

westend
Explorer
Explorer
troubledwaters wrote:
camperdave wrote:
Even with the disconnect switch on the off position, you will still have a small load...
That is not always true. When I turn my disconnect switch off, everything is off; there are zero loads connected.
Even the emergency battery powered brake system? That is the most important thing to have powered and should always be powered even with a disconnect switch interrupting any power to the trailer. It will draw no current when in the standard, non operating, position so isn't a drain on the battery(s). If the emergency brake switch on the trailer tongue is not powered, add a wire, a fuse, and the correct terminals from the switch to the battery, bypassing the disconnect switch.

The reason this is best practice is that it makes the emergency brake system operable, even with operator error of forgetting the switch before traveling.
'03 F-250 4x4 CC
'71 Starcraft Wanderstar -- The Cowboy/Hilton

fdwt994
Explorer
Explorer
The whole point of the battery disconnect is to prevent what happened to you from occurring in the first place. While storing the camper, turn it to "off" so the battery won't go dead. Also, if you turn the battery disconnect off and still notice the converter is on (electronic looking thing, ours is under the queen bed), be sure to turn it off also. Ours stays on even when the battery disconnect is turned off so it's important to check or it will drain the battery down as well.

In the winter time, if you're in a cold climate, I would recommend bringing the battery indoors and keeping it charged. Although campers usually come with deep cycle batteries, a battery is happiest when it's near or fully charged. Full discharge can eventually damage the battery and reduce its overall capacity.
2018 F250 6.2 Crew Cab
2018 Salem Hemisphere GLX 312QBUD
A family who loves to camp!

Jebby14
Explorer
Explorer
^ me thinks op is gone
Q: Whats brown and sticky???

A: A Stick....

Ava
Explorer
Explorer
With the amount of knowledge needed here, the OP should go back to the dealer and ask for a full explanation on how to work all the systems on the brand new rv.

troubledwaters
Explorer
Explorer
camperdave wrote:
Even with the disconnect switch on the off position, you will still have a small load...
That is not always true. When I turn my disconnect switch off, everything is off; there are zero loads connected.

2oldman
Explorer
Explorer
Npdchief07 wrote:
So when not in use I should have the battery disconnect turned to off?
They should call it a battery connect. That way it makes more sense to be "off."
"If I'm wearing long pants, I'm too far north" - 2oldman

camperdave
Explorer
Explorer
Even with the disconnect switch on the off position, you will still have a small load. On my motorhome, the propane detector is always powered, even when the 'disconnect' switch is off. A few other little things too, like the electric steps and I don't remember what else offhand...

For long term storage (anything more than 2 weeks), I pull the cable between my batteries (dual 6 volters).

And I'd highly recommend the link time2roll posted. Even if you are not mechanically/electrically inclined, understanding the electrical ins and outs of your RV will be very worthwhile. That page is a classic, written a long time ago and still stands the test of time.
2004 Fleetwood Tioga 29v

time2roll
Explorer II
Explorer II
Npdchief07 wrote:
So when not in use I should have the battery disconnect turned to off?
Yes. Unless you plug in then it may as well be on to get the charge topped up.

The 12 Volt Side of Life

opnspaces
Navigator
Navigator
The battery powers basically everything electric in the trailer except for:
  • Air conditioner
  • Microwave
  • All the 120v (household style) outlets)
  • The converter/charger which charges the battery

All of those items above are powered by plugging your shore power cord into an outlet. Everything else is powered by the battery.

Even if you turn off everything in the trailer there are parasitic loads, things like the propane alarm and memory settings on entertainment system that are always on and draining power from the battery. These parasitic loads can drain a fully charged battery in 1-2 weeks.

If you are able to plug into a 120v outlet at home the converter/charger in your trailer will charge the battery back up.

Having the battery drain below half it's capacity is damaging to the battery. If you cannot plug in to a power source you should use the disconnect switch.

Except if you are using the refrigerator it needs to use the battery or be plugged in, even when it is running on propane.

So basically if you are parked in your driveway you might as well plug it in and keep the battery charged. But you should also check the water level in the battery at least once a month until you get an idea how fast the water is evaporating. Letting the water level drop and exposing the plates is also damaging to the battery.
.
2001 Suburban 4x4. 6.0L, 4.10 3/4 ton **** 2005 Jayco Jay Flight 27BH **** 1986 Coleman Columbia Popup

2oldman
Explorer
Explorer
Npdchief07 wrote:
What exactly does that battery power?

I don't understand electrical. I don't know a volt from an amp.
Everything 12v: lights, jacks, slides, refer control board, furnace control.

Volt = pressure
Amp = volume
"If I'm wearing long pants, I'm too far north" - 2oldman