Forum Discussion

bobcouch's avatar
bobcouch
Explorer
Jun 21, 2014

Thought I knew - now I'm confused

When I got my 5th wheel back from the shop, I thought the battery was toast. It had several dry cells and read 2.3 volts post to post. Long story short, after adding water and charging for three full days it was back up to 12.9. Don't know how long it will last, but OK for now.
That leads to my question.
When I reinstalled the battery, I found that both the lift motor and the motor for the slides work regardless of the position of the battery bypass switch.
So - what does it actually do? Where is it actually located in the circuit?
I've always assumed that ON meant the battery was connected and OFF meant it was not. Now I'm not sure of anything. :h

5 Replies

  • That is why I installed a 250a race car cutoff switch on my Batt bank. Everything is off and my solar maintainer keeps them up. So every trip I know I have a full charge. Also safer when stored, I don't have to worry about a short starting a fire or damaging things.
  • In 2009 we went to Ontario in our class C. While there, the coach battery went dead and wouldn't take a charge. Dragged it out for a look and discovered the top of the plates were exposed. I put 2-1/2 bottles of water in to top off the cells and after a few hours charge FIL put his load tester on and it showed good. That battery soldiered on until we sold the MH. May even be still going.
  • More times than not the front landing gear, slide out motors and rear stabilizer motor are wired DIRECTLY to battery with their own fuses/dc circuit breakers before the battery disconnect switch.
    Also the LP Detector.

    Battery disconnect kills battery power to DC Dist. Panel.......lights, pump, furnace, control circuits, etc.
  • bobcouch wrote:
    When I got my 5th wheel back from the shop, I thought the battery was toast. It had several dry cells and read 2.3 volts post to post. Long story short, after adding water and charging for three full days it was back up to 12.9. Don't know how long it will last, but OK for now.
    That leads to my question.
    When I reinstalled the battery, I found that both the lift motor and the motor for the slides work regardless of the position of the battery bypass switch.
    So - what does it actually do? Where is it actually located in the circuit?
    I've always assumed that ON meant the battery was connected and OFF meant it was not. Now I'm not sure of anything. :h
    That's not good for any battery. Have it load tested as voltage doesn't tell the complete story.

    A switch at or near the battery post will disconnect everything. But you may still have 12V from the charger or solar.

    The typical bypass switch is set up to turn off lights etc when you leave. But hopefully not the refer.

About Technical Issues

Having RV issues? Connect with others who have been in your shoes.24,344 PostsLatest Activity: Dec 22, 2025