Fob eating batteries

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by butchbs1985, Feb 21, 2018.

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  1. butchbs1985

    butchbs1985 Taking things apart is fun!

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    A couple weeks ago the battery in my fob died. No big deal as it was 2 years old or so. I had bought a 5 pack of energizer batteries the last time it died so I changed it. Three days later, dead again, replaced it. Figured old batteries. Three days later, dead. Replaced it and ordered new Duracell batteries. Three days later, dead. Put in a Duracell with expiration date of 2025. That lasted about 9 days I think. This morning, dead.

    What's going on? All the buttons work so they're not stuck. No new keys on the ring. When I press the buttons with fresh batteries, I see the red light on the fob. I don't remember if that means anything.

    The next step is a Walgreens battery but I can't believe that the Duracell batteries that I bought are inferior. (purchased two from Amazon)

    I really don't want to shell out for a new fob but the battery situation is annoying.
     
  2. bisco

    bisco cookie crumbler

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    this has been an ongoing problem with not many solutions. if none of the buttons are stuck, try cleaning the insides.
     
  3. Air_Boss

    Air_Boss Senior Member

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    Sounds like a current draw or short in the FOB. Remove battery, clean the compartment with compressed air, clean the button assembly with alcohol then compressed air, being careful to note any dirt deposits or breaks in the membrane covering the buttons, and cleaning those, then see if the next battery performs better.
     
  4. butchbs1985

    butchbs1985 Taking things apart is fun!

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    Bummer. I tried searching but had a hard time distinguishing just this fob. I'll clean it out as best I can and keep trying. Thanks.
     
  5. Colin

    Colin Junior Member

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    You can also clean contacts using a pink pearl pencil eraser or contact cleaner. Oddly the pencil eraser is better.
     
  6. butchbs1985

    butchbs1985 Taking things apart is fun!

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    I'm on a 7 day cycle even after cleaning. I guess it's time to search for pricing on a new fob. It'll wear out being taken apart at this rate. I'll spray it with contact cleaner when I get some but that's all I've got left.
     
  7. schneids

    schneids Junior Member

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    =========================================================================

    Yes, I'm having the same prob with an '11 key fob. I've been putting a new battery in about every 3 days. Last night I bought a new battery [CR1632 by the way] at walmart. Put it in - led lit up bright red when I pressed a button. This morning, pushed a button to try it - no led light - totally dead. This is about the 6th battery I've put in it. Everything looks clean inside. Don't know what the problem is.

    The only other thing of relevance, I had the car in to the body shop and it started after I got it back from them. I know they disconnected the battery while it was there - because all my radio station presets were gone. So don't know if disconnecting the battery and resetting the car caused something. But last night, my fob wasn't anywhere near the car - at least 60+ feet away and thru some walls....
     
    #7 schneids, Mar 27, 2018
    Last edited: Mar 27, 2018
  8. Erik Owens

    Erik Owens Member

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    Test those batteries and make sure they are dead. Also if you hang your keys close to your vehicle then separate them. And one more issue might be the internals to the FOB themselves. Corrosion can make those FOBs act funny like unlocking or locking vehicle on its own or triggering the panic function again and again. Open it up if yo have a small enough screwdriver and check our the circuitry to make sure there is no white crusty or green crusty.
     
  9. butchbs1985

    butchbs1985 Taking things apart is fun!

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    I've ended up swapping fobs with my wife and so far, so good. This tells me that perhaps a button is sticking and since she hardly uses it, it's lasting longer. I also drowned it in contact cleaner but went through another battery after that. Maybe something finally loosened up.
     
  10. Erik Owens

    Erik Owens Member

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    Good deal. I know spending money sucks unnecessarily but save for a new FOB and keep that sucker dry in a bag of rice from now on. But glad you found it.
     
  11. schneids

    schneids Junior Member

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    Well the batteries themselves aren't dead - they do measure 2.6v. From what I've seen, 2.7v seems to be the lower limit for the fob to still work. But that doesn't matter - the fob is DEAD - as in "does not work" - have to use the key to manually unlock car. I've looked over the circuit board - everything looks clean and I can't see where anything looks shorted. What I will do over the next couple of days is hook my meter up to it and see what the current draw is. I'll post that info and if I get time, will take some pics of the inside of the fob and post them too. The latest now is, I'll put a new battery in it in the morning and by evening the fob is dead. I might also try pulling the battery out of it when I'm not using the fob and just putting it in when I need to use the fob.
     
  12. Air_Boss

    Air_Boss Senior Member

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    Corrosion may have consumed the circuit board traces.
     
  13. schneids

    schneids Junior Member

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    No - there is NO corrosion in the battery compartment or anywhere else in the fob.... let me get my camera and see if I can get a couple of pics....... There's a couple shots of each side - circuit board looks clean - no corrosion or crud..... Now, I did use some wires and tried to measure the current. On the mA scale, it measure .45mA - when I put it on the uA scale, it measured 4.5uA - heh - so not sure what it's exactly drawing, but if it's 4.5uA - shouldn't be a prob and should last forever.....
    DSCN1274.JPG DSCN1277.JPG DSCN1279.JPG DSCN1285.JPG
     
  14. Andyprius1

    Andyprius1 Senior Member

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    There is also a return spring for the actuator buttons, all insulating materials are still in fob? the two covers close properly? Compare with your wife’s. Lastly it may help to reboot, so computers learn what they are doing again. I believe on a new fob the voltage level is something over 3V, like 3.2V. Just some ideas It sounds like a internal short that’s eating up the battery. One more idea, insert a small thin piece of paper as a insulator on any ares that are dubious. Most obvious: a stuck button.
     
    #14 Andyprius1, Apr 7, 2018
    Last edited: Apr 7, 2018
  15. schneids

    schneids Junior Member

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    I only have the one fob. Return spring for the actuator buttons??? They're built into the switches. I doubt any buttons are stuck - I can hear them "click" when I press the button in and again when I release the button. When the fob quits working, the battery is at 2.6V. It's only a 3V battery - but I think a new one is usually around 3.2V. Yes, there is some kind of short in the fob - but I sure can't find it, and everything looks clean inside. I made an aluminum foil case for the fob - to see if it was getting some kind of signal that was sucking the battery down. Put a new battery in it one night, shoved it in the Al case, and in the morning the fob was dead. So it's definitely something in the fob.

    So, what I've resorted to now is to pop open the case and pop the battery out when I get home.Then just slap it together when I have to go somewhere. I guess I'll have to get a new fob from the dealer [thought I read that '11 has to be done by dealer or have one of the machines to program the car??].....
     
  16. schneids

    schneids Junior Member

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    Update - well my fob is still eating batteries. What I do now is, after I start the car, I take the battery out of the fob. Then when I get to where I'm going, I take the mechanical key in with me - unlock car with that when I come out, use fob to get car started, and then take battery out. It's a royal pain - but it works. I've also ordered another fob from ebay [same numbers on it]. So now I"ll have to see about programming the car to take it - or pay to have the dealer do it.

    Another thing I noticed that I find interesting is - if the fob is not working from low battery, when I go to start it and push the start button, it will say to hold the fob by the start key. When I do this, it will beep and then I can press the start button and it will start [oh, I have an '11]. Now the interesting part is - this will work even if I don't have a battery in the fob. So it must be transmitting something - even with no battery in it....???? How does it do this???
     
  17. Air_Boss

    Air_Boss Senior Member

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  18. mikefocke

    mikefocke Prius v Three 2012, Avalon 2011

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    In another car it is called a pill. On my windshield, I put a sticker containing a RFID passive device that opens a gate to the community.
     
  19. Erik Owens

    Erik Owens Member

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    Our FOBs are touchy anything below 3.0 volts then they normally start tweaking out. Like setting off alarm, or continuous locking/ unlocking hell like now killing your batteries prematurely. 2.9 and below is where I change them out and go on about my way.
     
  20. grantb3

    grantb3 Junior Member

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    I also wonder about the failure modes with these FOBs. Both of mine now work perfectly some days, other days intermittently and even in some cases I get "KEY NOT DETECTED". Everything looks fine, battery is good (3v unloaded) and I've replaced it anyway. I wonder if the board develops cracks or the solder joints break. I have a microscope so I might look at it this weekend. BTW, the switches should be replaceable by the brave. I did one in a logitech mouse recently and it was pretty similar. So odds are good that the switches can be purchased if one can determine a part number. Some place like Mouser.com would likely have them.
     
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