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Npdchief07's avatar
Npdchief07
Explorer
Aug 26, 2019

question about battery

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

  • 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.
  • 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
  • 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.
  • 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
  • You household electric 120vac runs a converter (battery charger) to charge the battery. The battery is the reserve power to run 12vdc intermittent items such as your slides - power awning- power jacks and small 12vdc drain items such as lights. The a/c and water heater (if heating on electricity) requires you to be plugged in on 120vac. The battery disconnect is used to turn off the battery to everything in the rv during storage. If the rv sits for a period of time with the batteries not disconnected and not plug into 120vac the rv still has a small drain on the battery and will run it down over a period of time. The converter is not designed to run the 12 vdc power alone it needs the battery reserve so the larger 12v drain items is not pulling power solely of the converter.
  • yes though if you are close enough to home to be plugged in why not leave the unit plugged in so its ready to go and fully charged all the time. during the camping season when my unit it home its plugged in. battery starts every trip full and fridge is cold so all we need to do is toss the food in. also allows me to run the air if im going to be working in the camper or cleaning it I can cool it down.
  • So when not in use I should have the battery disconnect turned to off?
  • The battery disconnect switch disconnects the battery from the TT. When the battery has been disconnected and you aren't plugged into shore power, pretty much nothing will work in the RV. The lights use 12v battery power as do any fans. The furnace and fridge both use 12v as well as any USB/12v power outlets. Most propane/CO detectors use 12v as well. The smoke detector most likely uses a 9v battery.

    If the battery is in the On position, it is not disconnected and the battery will drain pretty quickly.

    -Michael