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Rapid Key Fob Battery Drain

Discussion in 'Gen 3 Prius Technical Discussion' started by RRxing, Apr 11, 2017.

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  1. RRxing

    RRxing Senior Member

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    A recent issue has reared it ugly head regarding my key fob batteries. I replaced the CR1632 battery in one of the fobs a couple of months ago when its original battery died. I left the spare fob without a battery, but had a new one available for future use.

    A few days ago the fob no longer worked. Weird, it's a relatively new battery - Anyway, I replaced it with the spare. A day or two later, you guessed it - dead fob again.

    Bought two new batteries and put one in the spare fob I had in the drawer. Worked fine for a day or so, then another dead battery.

    I have done absolutely nothing different as far as where I normally keep the fobs. I know what the manual says about keeping the fobs near TVs, cell phones, etc., but this does not apply. There are no new electronics in the house to possibly cause the batteries to drain. What I find frustrating is that the same thing happens with BOTH fobs. I did a close inspection of the circuit boards and found nothing obvious, like oxidation on the contacts or visible damage.

    The last new battery read 3.2VDC out of the package. It now reads 2.7VDC after about an hour in the fob. Again, this is happening with both fobs. Again, nothing out of the ordinary as far as where I normally keep the fobs.

    Cue Sarcasm - By process of elimination I can only surmise that someone in the neighborhood recently installed a Tokamak reactor and didn't get the proper permits - End Sarcasm.

    Having to use the manual key to lock/unlock the car is getting old (I know - 1st World Problem). Putting the fob on the Power button to start the car works fine, so I don't think there's a problem with the handshake between fob and car.

    Does anyone have any suggestions short of buying a new fob or two? Thanks in advance.
     
    #1 RRxing, Apr 11, 2017
    Last edited: Apr 11, 2017
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  2. RRxing

    RRxing Senior Member

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    I'm going to have a co-worker check out the circuit board(s) next week to see if one or more of the buttons are acting as if depressed. The buttons seem to be working okay but that might just be wishful thinking on my part...

    Is there anybody out there?
     
    #2 RRxing, Apr 12, 2017
  3. spiff72

    spiff72 Member

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    I had one of my two fobs drain very quickly after a battery replacement several years ago (it lasted about a week). I just swapped it out for the spare and never had an issue again. I checked the voltage over the course of a couple of hours and it dropped similarly to yours.

    Actually i probably need to re-visit the old fob and see if it is still draining quickly.
     
    #3 spiff72, Apr 12, 2017
  4. IMkenNY

    IMkenNY Im just being nosy

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    Are you using name brand cr1632 cells?
    I found several lots off EBay and amazon tested good with a meter but yielded very short lives.
    I have since switched to Panasonic cells and I have not had any additional problems.
     
    #4 IMkenNY, Apr 12, 2017
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  5. RRxing

    RRxing Senior Member

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    I've been using Energizer CR1632 batteries. I tried but couldn't find any Duracell's locally. I'm not at the point where I would order any online yet - I want to find out if the issue is with the fobs themselves.
     
    #5 RRxing, Apr 13, 2017
  6. bisco

    bisco cookie crumbler

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    shouldn't a new battery be 3.3v?
     
    #6 bisco, Apr 13, 2017
  7. RRxing

    RRxing Senior Member

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    I rounded down. It read 3.2+VDC
     
    #7 RRxing, Apr 13, 2017
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  8. bisco

    bisco cookie crumbler

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    try shielding the spare fob, and see if the voltage drops.
     
    #8 bisco, Apr 13, 2017
  9. RRxing

    RRxing Senior Member

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    I don't keep a battery in the spare, but I'll put a new battery in one of the fobs and then wrap it in aluminum foil, let it cook for a while, then see what happens.
     
    #9 RRxing, Apr 13, 2017
  10. Former Member 68813

    Former Member 68813 Senior Member

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    How about improper installation and shorting the battery? Furthermore, touching battery or the insides with sweaty hands can leave conductive tracks. Clean everything with pure alcohol and only use genuine batteries. I understand there are counterfeit "energizer" batteries on eBay and Amazon.
     
    #10 Former Member 68813, Apr 14, 2017
  11. ALS

    ALS Active Member

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    I got smart and got the lifetime battery replacement from Batteries Plus or Batteries and Bulbs or what ever they call it now Batteries - Phone Repairs - Light Bulbs - Chargers - Batteries Plus Bulbs. The original lasted almost two years and the next two replacements lasted less than nine months. Bought the life time battery replacement, for watches and Key fobs, (twice the normal price) and I get free replacements every time the battery dies in the fob. Funny how the battery seems to last longer when they have to pay for the replacement. I just walk in hand the employee the fob and they install a new battery and hand it back to me free. I wouldn't recommend getting the free battery replacement unless your planning on keeping the car for more than a few years.
     
    #11 ALS, Apr 18, 2017
    Last edited: Apr 18, 2017
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  12. RRxing

    RRxing Senior Member

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    UPDATE: I told someone at work about the fob battery drain who then asked me if I had remote start on the car. I do. He said his parents car had remote start and suffered the same issue with fob batteries dying. He said he disconnected the remote start and the problem went away. I'm going to do some troubleshooting when I get a chance to see if the hood switch may be stuck or if there is an easy way to disable the remote start, then try a new battery in the fob...the saga continues...

    Actually, I'm going to start by disconnecting the negative on the 12V battery and then put a new battery in the fob to see if the drain occurs. If no drain occurs, then at least I'll know there is a continuous handshake between the fob and car. I'll proceed with the remote start from there...
     
    #12 RRxing, Apr 24, 2017
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  13. RRxing

    RRxing Senior Member

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    Update II: So I finally got around to do some additional troubleshooting (been kinda busy lately.)
    Test #1 - I put a new battery in the fob and placed it inside 2 RF-resistant bags and waited a few hours. No luck, battery drained.
    Test #2 - I disconnected the 12V in the Prius (it read 12.58VDC) and then put a new battery in the second fob and waited an hour or two. Again, no luck, the fob battery drained.
    Conclusion - Both fobs have a short which is draining the battery,
    OR
    There is some new, strong RF signal in or around the house.

    I think I'm just going to live with this first-world problem.
     
    #13 RRxing, Jun 18, 2017
  14. bisco

    bisco cookie crumbler

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    did you remove the remote starter?

    maybe go for the lifetime battery replacement mentioned above.
     
    #14 bisco, Jun 18, 2017
  15. kc410

    kc410 Active Member

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    OR
    The "new" batteries you have been using are not in the best of condition when installed.
     
    #15 kc410, Jun 18, 2017
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  16. RRxing

    RRxing Senior Member

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    Six different batteries from three different locations? Half of which I checked having >3.1 volts prior to install? I don't think that's the issue...
     
    #16 RRxing, Jun 18, 2017
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  17. RRxing

    RRxing Senior Member

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    I'd be going through a dozen or more batteries a day...
     
    #17 RRxing, Jun 18, 2017
  18. RRxing

    RRxing Senior Member

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    With the 12V disconnected, nothing would be going off a signal.
     
    #18 RRxing, Jun 18, 2017
  19. bisco

    bisco cookie crumbler

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    too bad there isn't a way to try a new fob without buying it.
     
    #19 bisco, Jun 18, 2017
  20. Former Member 68813

    Former Member 68813 Senior Member

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    Anything less than 3.3v is bad. Trust me. I went through that before, feel free to search here, and problem went away when I cleaned the fob and used swiss made Renata cells (less likely to be fake). fake CR1632 - Google Search
     
    #20 Former Member 68813, Jun 18, 2017
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