Battery Box Creating Interference with Car Fob

AdosHouse on 26/03/2023 - 20:46

So I got a console fridge from 4wdSupaCentre so I can take lunch from home (I am a mobile tech). This fridge plugs into the cigarette port but the port is only live when the car is on so I am finding the fridge warms up too much while the car is off.

To solve this I recently bought an AGM battery and battery box to run the fridge while I'm working, and I'll just charge it every few days at home. But I have now discovered that the setup is creating interference which is stopping my car remotes from working more than a couple of metres from the car, sometimes not even that close. The battery box sits behind the drivers seat and the fridge behind the passenger front seat. But I'll point out that just the fridge had no problems.

Does anyone have any suggestions for reducing the interference? Or any workarounds, etc?

Automotive

Comments

  • Hybroid on 26/03/2023 - 20:47
    +1

    Change the battery in your key fobs.

    • AdosHouse on 26/03/2023 - 20:54
      +1

      Car is one year old, with only 4 month use (fleet vehicle). The remote I do use, changing the battery is the first thing I thought of doing, changed nothing. Tested the unused spare key same results.

  • pegaxs on 26/03/2023 - 20:52

    It's a battery… in a box… I dont think it is creating the interference… unless there are some heavy duty electronics to run your battery. Do you have coiled up cables/wires near the battery/fridge?

    Get a power outlet wired into the car that is always on or move the AGM to the boot or under the bonut and get an outlet wired into the vehicle and set the alternator up to charge it.

    • AdosHouse on 26/03/2023 - 20:56
      +1

      Fleet vehicle, I can't change stuff.

      My father just suggested that the box has a 5v USB sockets and it might have some very cheap (coughKings gearcough) switching power circuitry which may cause interference. Will test that soon.

      • GordonD on 26/03/2023 - 21:01

        First test scenario would be to disconnect whatever you don't need in the battery box. Temporarily or permanently. Until you identify what the RFI is coming from.

        • AdosHouse on 26/03/2023 - 21:15
          +1

          Okay, progress was made. Its not the battery box, it's the fridge. Even when the fridge is turned off and just has standby power it is interfering. How the hell does that work?

          • MS Paint on 26/03/2023 - 22:06
            +2

            @AdosHouse: It's an RFridge

          • outlander on 26/03/2023 - 23:01
            +1

            @AdosHouse: Might be a buck converter used to take the 12v, and drop it to something the display circuitry can use. Easiest thing to do is just swap the unit

            Sounds like it's generating RF and overwhelming the receiver inside the car. Best way would be to find the faulty component and fix it, but given we can't see RF in that spectrum it's kinda hard. Shielding is the next step, but it's a lot harder to do well. Aluminium foil wrapped in clear packing tape feels like one place to start. Best done inside the unit though, which has warranty concerns.

            I remember I had cigarette port duplicator with USB ports, and I had to cut out the USB ports because it was interfering with the radio.
            Maybe you could put a radio close to it and see if the radio gets static? Most phones seem to still contain a FM reciever in them, but require you to connect headphones because it uses the headphone wire as an antenna. Assuming a radio does pick up the noise, maybe you could wave the wire around and see where it's strongest.

  • GordonD on 26/03/2023 - 20:59

    What is normally referred to as a battery box is just a box to put a battery in. There is nothing in a battery box to cause interference. By a battery box, do you mean something more complicated than that? I'm wondering if you do, because if you have a separate battery powering the fridge, you must be recharging it somehow, and that would require some electronics that could be generating interference.

    The simpler solution would have been to rewire your cigarette lighter socket, or fit another one, that doesn't go through the ignition switch.

  • GordonD on 26/03/2023 - 21:24

    So tell us a bit more about the fridge.

  • CurlCurl on 26/03/2023 - 21:30

    The fridge is earthed through the vehicle when using the cigarette lighter.The fridge may need to be earthed to the vehicle.

    • AdosHouse on 26/03/2023 - 21:34

      Worth a shot. Problem is that I can't verify that may be an issue since I can't use the remote when the car is turned on. And to power the fridge when it is connected to the cigarette port the car needs to be on. But I'll try running a cable from the negative on the battery to a nut somewhere close by. I'll have to do that in a few days though since I'm getting my gallbladder out in the morning.

      • GordonD on 26/03/2023 - 21:41

        Try what CurlCurl suggests to see if its an earth loop. I'd also talk to the supplier, since you have purchased both the fridge and the battery box from them they can't blame someone else. If its a "feature" of the fridge they should be aware of it from other customers. If its a fault with your unit it should be fixed. Since the fridge is able to run on anywhere from 12V to 24V it must have a DC-DC inverter to do that. That's where I'd be suggesting the problem might be coming from if its feeding RFI back up the power cable.

        If they aren't helpful, your idea of wrapping aluminium foil around the power cable might be on the right track. A power cable made out of shielded cable might help.

        • AdosHouse on 26/03/2023 - 21:55

          Yep I'll be trying all that. Just later in the week when I feel better.

          Thanks for your help, I have a starting point now.

  • phila63 on 26/03/2023 - 22:40
    +2

    Maybe try a ferrite choke on the power lead.

    • GordonD on 27/03/2023 - 09:26

      Good thought.

    • AdosHouse on 27/03/2023 - 18:33

      Just tried that, no love.

      • phila63 on 28/03/2023 - 19:46

        Choke on both ends maybe

  • AustriaBargain on 26/03/2023 - 23:29

    Hold your fob up to your head, or put it in your mouth, to boost the signal

    https://www.carthrottle.com/post/the-science-behind-why-your…

  • altomic on 27/03/2023 - 09:12
    +1

    faraday cage for the battery /box ?

    • AdosHouse on 27/03/2023 - 18:33

      Super tempted at this point.

  • pinchies on 27/03/2023 - 09:16

    This sounds like the fridge is definitely emitting RF noise. Return it to place of purchase as a major fault.

    • AdosHouse on 27/03/2023 - 18:33

      That looks like it will be happening.

  • Marty156 on 27/03/2023 - 10:19

    Most remote key FOBs operate around the 433 MHz range. Antennae for this is usually inside the door panels.
    For a test,
    Try moving the fridge to centre console or middle of back seat.
    Try a bypass capacitor across the power input on the fridge itself (inside the terminal block)

    Best would be to place fridge in boot, as far from (if car has one) the receiver for the boot lid.

    • AdosHouse on 27/03/2023 - 18:34

      Fridge is in the back seat passenger side footwell, I can't use the remote more than 2m from the car on the drivers side.

      • Marty156 on 27/03/2023 - 19:37

        Does it work further away if the driver's DOOR is open or closed?

  • jonkvh on 27/03/2023 - 16:23

    I'd try running the fridge off an inverter, won't have to charge the battery so often.

  • Stewardo on 27/03/2023 - 18:31

    Put some ice bricks in your fridge when you put your lunch in it.

  • AdosHouse on 27/03/2023 - 18:38

    Okay so this is what I have tried so far.

    1) Disconnecting all the other connections in the battery box except the anderson plugs.
    2) Using the cigarette port on the battery box instead of the anderson plugs.
    3) I put a ground cable from the battery negative to the chassis (after making sure the car is definitely negative grounded)
    4) Wrapping the fridge power lead in aluminum foil in case its the cable doing anything
    5) Put a ferrite choke on the fridge power lead.

    None of that worked. Range with the fridge plugged in but NOT EVEN TURNED ON is only 1-2m. Unplug the fridge and back to normal.

    Looks like the fridge will have to go back. I am willing to bet the store won't want to exchange it though since technically the fridge works fine.

  • AdosHouse on 28/03/2023 - 23:18

    Okay so I took it back to the store today, bit of a pain dealing with the staff but we will see how you go.

    So I explained to the staff member what it was doing and what I had tried. He was just on loop about how he has never seen that before. I was plugging it in, testing the remote, unplugging it, testing the remote, to demonstrate it was happening. He got me to try removing my ground strap in case that was causing it?? Then he started saying that it wasn't a warranty job because I can't prove it's the fridge. I replied with , you are literally watching me plug the fridge in and the issue is happening, then unplugging the fridge and the issue is disappearing. Then he said yeah but we can't prove it's the fridge (on a loop here), I said there is only 3 items there (battery, box, and fridge) and they are all your brand so fix something.

    I then convinced him to go grab the demo model and we can test it. Plugged it in in the same spot of the car and nothing changed and magically the problem went away. So they have agreed to send mine back to the manufacturer for further testing. Let's see how this goes.

  • CurlCurl on 29/03/2023 - 16:53

    Then he started saying that it wasn't a warranty job because I can't prove it's the fridge. I replied with , you are literally watching me plug the fridge in and the issue is happening, then unplugging the fridge and the issue is disappearing. Then he said yeah but we can't prove it's the fridge (on a loop here), I said there is only 3 items there (battery, box, and fridge) and they are all your brand so fix something

    That's why I never buy from 4wdSupaCentre.

    • AdosHouse on 29/03/2023 - 19:58

      Yeah I'm starting to get this hint. I just wanted cheap stuff though, because it's in a work car and it could change to something else at any time and it might not fit all this in it.

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