Announcement

Collapse
No announcement yet.

Battery Reversal is a real thing

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Battery Reversal is a real thing

    This is more posted for educational experience, We've already solved the problem. No Photos or Video's to document this.

    I was at the campground, and I was helping a friend that had just bought a used camper this year.

    His complaint was the battery doesn't last long (maybe 4 hours) and even fresh off the charger, it doesn't have enough reserve power to get the slideout all the way out without leaving his truck connected. Diagnosis: Dead Battery. I (Incorrectly assumed) the battery was original to the 2016 camper. 5-7ish years is the average lifetime on a standard sealed lead-acid battery. No big deal.

    The battery died at 9pm on his first night. We took photos of how the camper was connected, and he purchased two new Group 24 batteries, and some 2/0 cables to wire them in parallel. When we reconnected to the new battery, Immediately the 30amp fuse on the camper tongue blows. Weird?

    We take battery out of parallel, to simplify. Still blows the fuse Immediately. (and with some pretty large sparks) We play with order of operations for a little bit. (Let's try putting the fuse in first, then connecting,. Nope. Let's try connecting, then putting the fuse in, Nope. Try turning EVERYTHING in the camper off, nope).We hook the old battery up, still works normal (just with no real power)

    Now we start examining everything. In the dark at 10pm.
    The fuse was on the cable connected to negative terminal. It was manually spliced in after the fact (with green wires), and we hypothesized that it was being used as a disconnect switch. (It's the only thing that made sense).
    We tried a 40amp fuse, just incase the 30amp's were flaky. Nope, blew immediately.

    We compare the pictures, we're hooking it up exactly the same way. We examine the "old" battery. It's dated 2019. Huh? It shouldn't be this bad off.
    It's time to phone a friend. We call a friend who works on Semi's, and usually does the 12V systems on them.
    We explain everything. We get silence for almost a minute. Then he asks us to take a voltage reading off the "old" battery, and send him a photo of it.

    It's -12.76.

    Negative 12.76 volts.

    We missed the - sign on the multi-meter, because it's not backlit, and really, who expects your battery to put out negative power.

    We reverse the leads (positive to negative, negative to positive), and Voilà! it works!

    Semi-Guy has heard stories. If you get a battery discharged enough, and then get it on the charger backward, you can reverse the polarity of a battery. We can only assume it's incredibly dangerous to do.

    Friend is going to get some colored electrical tape, and correct the wire color when he get's back. But now the fuse makes total sense, since it's REALLY on the positive side.

    Just figured I'd share a fun story from the weekend.

    Mike
    2017 Imagine 2800BH pushing a 2019 Ford F150 Platinum

    Formerly: 2002 Rockwood Popup
    Location: Massachusetts

  • #2
    Interesting.
    Ted
    2021 Reflection 310RLS
    2020 F350 PS,CC,LB,SRW

    Comment


    • #3
      mpking GF's BIL had 1 black and 1 white cable on his camper. He made that mistake a couple of times because he kept thinking the black cable was negative when it was positive. After several incorrect attempts late in the night at the hunting lease, he resorted to red and black electrical tape.
      Joseph
      Tow
      Vehicle: 2024 GMC K3500 Denali Ultimate Diesel
      Coach: 303RLS Delivered March 5, 2021
      South of Houston Texas

      Comment


      • #4
        I have definitely seen this before, I never trust the color of the wires, always look for which one is going to the frame, or if its not my rig and I am not sure of how its wired grab a meter and check resistance between the cable that should be negative and the frame. You would not believe how some things are wired out there.
        Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

        Neil Citro
        2018 Reflection 28BH Pepwave
        2019 F350 6.7L Long Bed Crew Cab

        Comment


        • #5
          RV builders tend to “think” in shore power colours where black is power and white is neutral (ground). They apply this to 12V systems throughout the trailer. Caution is definitely required. I have never heard of “reversing” a battery polarity . . . sounds dangerous.

          Rob
          Cate & Rob
          (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
          2015 Reflection 303RLS
          2022 F350 Diesel CC SB SRW Lariat
          Bayham, Ontario, Canada

          Comment


          • #6
            Cate&Rob Rob, I think that is why the new converters have "reverse polarity fuses" to keep this from happening. However is the battery is DEAD enough, the fuses will not blow.

            I do think I have seen this before, I'm guessing 40 ish years ago and that is probably the only time I have ever seen it.
            Joseph
            Tow
            Vehicle: 2024 GMC K3500 Denali Ultimate Diesel
            Coach: 303RLS Delivered March 5, 2021
            South of Houston Texas

            Comment


            • #7
              WOW, Mike mpking ! First I have heard of this too. Good thing solved and nothing too serious went wrong or folks were hurt - yikes ! Thanks, for sharing.

              Dan
              Dan & Carol
              2014 303RLS Reflection #185 (10/2013 build)
              2012 Silverado LTZ Crew Duramax 2500HD - 2700/16K Pullrite Superglide

              Comment


              • #8
                Yeah I am pretty sure the time I saw it was on an old time battery charger connected backwards to a really dead battery. Would be hard to do with anything with "smart" electronics.
                Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

                Neil Citro
                2018 Reflection 28BH Pepwave
                2019 F350 6.7L Long Bed Crew Cab

                Comment


                • #9
                  Originally posted by mpking View Post
                  This is more posted for educational experience, We've already solved the problem. No Photos or Video's to document this.

                  I was at the campground, and I was helping a friend that had just bought a used camper this year.

                  His complaint was the battery doesn't last long (maybe 4 hours) and even fresh off the charger, it doesn't have enough reserve power to get the slideout all the way out without leaving his truck connected. Diagnosis: Dead Battery. I (Incorrectly assumed) the battery was original to the 2016 camper. 5-7ish years is the average lifetime on a standard sealed lead-acid battery. No big deal.

                  The battery died at 9pm on his first night. We took photos of how the camper was connected, and he purchased two new Group 24 batteries, and some 2/0 cables to wire them in parallel. When we reconnected to the new battery, Immediately the 30amp fuse on the camper tongue blows. Weird?

                  We take battery out of parallel, to simplify. Still blows the fuse Immediately. (and with some pretty large sparks) We play with order of operations for a little bit. (Let's try putting the fuse in first, then connecting,. Nope. Let's try connecting, then putting the fuse in, Nope. Try turning EVERYTHING in the camper off, nope).We hook the old battery up, still works normal (just with no real power)

                  Now we start examining everything. In the dark at 10pm.
                  The fuse was on the cable connected to negative terminal. It was manually spliced in after the fact (with green wires), and we hypothesized that it was being used as a disconnect switch. (It's the only thing that made sense).
                  We tried a 40amp fuse, just incase the 30amp's were flaky. Nope, blew immediately.

                  We compare the pictures, we're hooking it up exactly the same way. We examine the "old" battery. It's dated 2019. Huh? It shouldn't be this bad off.
                  It's time to phone a friend. We call a friend who works on Semi's, and usually does the 12V systems on them.
                  We explain everything. We get silence for almost a minute. Then he asks us to take a voltage reading off the "old" battery, and send him a photo of it.

                  It's -12.76.

                  Negative 12.76 volts.

                  We missed the - sign on the multi-meter, because it's not backlit, and really, who expects your battery to put out negative power.

                  We reverse the leads (positive to negative, negative to positive), and Voilà! it works!

                  Semi-Guy has heard stories. If you get a battery discharged enough, and then get it on the charger backward, you can reverse the polarity of a battery. We can only assume it's incredibly dangerous to do.

                  Friend is going to get some colored electrical tape, and correct the wire color when he get's back. But now the fuse makes total sense, since it's REALLY on the positive side.

                  Just figured I'd share a fun story from the weekend.
                  I've seen batteries charged backwards on rare occasions as well as batteries labeled backward as well as one battery where the lug was labeled - and the case at the lug labeled +. Stuff happens.

                  Jim

                  Comment


                  • #10
                    It can happen. With a simple charger, you can discharge the battery with the charger reversed and then charge it reversed.

                    John & Kathy
                    2014 Reflection 303RLS
                    2014 F250 SC SB 6.2

                    Comment

                    Working...
                    X