Parasitic Drain - Bulb Trick

Discussion in 'General Motoring' started by sharx333, Nov 11, 2006.

  1. sharx333

    sharx333 Guest

    Just wanted to ask:

    Is the "light bulb" test (putting a 12v bulb in series with the battery
    circuit) an accurate test for a parasitic drain? My ammeter only goes
    up to 0.25A, and I don't want to risk overloading the meter.

    How bright should the bulb light up, if it should at all, for a
    "normal" drain? (clock, ECU, radio memory)

    Thanks!
     
    sharx333, Nov 11, 2006
    #1
  2. sharx333

    TeGGeR® Guest


    See the relevant page at Bill Darden's excellent Battery FAQ:
    http://www.uuhome.de/william.darden/carfaq10.htm
     
    TeGGeR®, Nov 11, 2006
    #2
  3. sharx333

    TeGGeR® Guest


    See the relevant page at Bill Darden's excellent Battery FAQ:
    http://www.uuhome.de/william.darden/carfaq10.htm
     
    TeGGeR®, Nov 11, 2006
    #3
  4. sharx333

    jim beam Guest

    sure, but it depends on the bulb and the drain!!! if you describe your
    problem, maybe we can address that question better?
     
    jim beam, Nov 11, 2006
    #4
  5. sharx333

    jim beam Guest

    sure, but it depends on the bulb and the drain!!! if you describe your
    problem, maybe we can address that question better?
     
    jim beam, Nov 11, 2006
    #5
  6. sharx333

    dold Guest


    I had a light bulb that was a parasitic drain, once.
    I thought I just had a dying battery. It was a little sluggish starting
    sometimes, and dead if I didn't drive it every day.
    I bought a new battery, and that made things much better, and then it was
    dead again after it sat for a few days.
    I charged it up, got in, and noticed a strange glow on the floor. At first
    I thought it was a street light, then I realized that the glove box light
    was on. The switch had gotten knocked out of it's mounting. I didn't see
    the dim light under daytime conditions, and only happened to notice it at
    night.
    I would say that a dual filament 1157 bulb should glow dimly. If it is at
    all bright, that is a pretty good load. At full brightness:

    bright filament: 12.8V, 26.9W, 2.10A (R=V/I=12.8/2.1=6.1 ohms)
    dim filament: 14.0V, 8.3W, 0.59A (R=24 ohms)
     
    dold, Nov 11, 2006
    #6
  7. sharx333

    dold Guest


    I had a light bulb that was a parasitic drain, once.
    I thought I just had a dying battery. It was a little sluggish starting
    sometimes, and dead if I didn't drive it every day.
    I bought a new battery, and that made things much better, and then it was
    dead again after it sat for a few days.
    I charged it up, got in, and noticed a strange glow on the floor. At first
    I thought it was a street light, then I realized that the glove box light
    was on. The switch had gotten knocked out of it's mounting. I didn't see
    the dim light under daytime conditions, and only happened to notice it at
    night.
    I would say that a dual filament 1157 bulb should glow dimly. If it is at
    all bright, that is a pretty good load. At full brightness:

    bright filament: 12.8V, 26.9W, 2.10A (R=V/I=12.8/2.1=6.1 ohms)
    dim filament: 14.0V, 8.3W, 0.59A (R=24 ohms)
     
    dold, Nov 11, 2006
    #7
  8. sharx333

    sharx333 Guest

    Sure, jim. And thanks.

    Last week, the battery drained overnight on my '95 Civic 1.6L. I took
    the battery to be recharged at a shop, and we found that the water
    level was low. But I suspected a "ground" somewhere, because I had just
    sprayed the engine with a degreaser and rinsed it (low pressure garden
    hose).

    Since my ammeter only goes up to 0.25A (250 mA), and I read on some
    posts that the current could go over 1A, I tried the bulb trick first.
    I don't know the exact rating of the bulb (aftermarket dome/trunk
    light), but it glowed brightly. (All doors/trunk was closed, key off)

    I tried pulling underhood fuses and even disconnecting the alternator,
    with no result. Then I tried pulling the cabin fuses, and I found that
    it was the Pioneer head unit that was pulling most of the power (for
    the preset memory, I guess).

    When I disconnected the radio, the bulb was finally very dim. I tried
    the ammeter and expected less than 80 mA (from the battery FAQ link,
    thanks to TeGGer). But I still got 170 mA or so. I've checked all the
    possible bulbs, and I think a bulb would pull more than that.

    I finally concluded that there was no parasitic drain at all, but I'm
    puzzled as to what could be making that extra load.
     
    sharx333, Nov 12, 2006
    #8
  9. sharx333

    sharx333 Guest

    Sure, jim. And thanks.

    Last week, the battery drained overnight on my '95 Civic 1.6L. I took
    the battery to be recharged at a shop, and we found that the water
    level was low. But I suspected a "ground" somewhere, because I had just
    sprayed the engine with a degreaser and rinsed it (low pressure garden
    hose).

    Since my ammeter only goes up to 0.25A (250 mA), and I read on some
    posts that the current could go over 1A, I tried the bulb trick first.
    I don't know the exact rating of the bulb (aftermarket dome/trunk
    light), but it glowed brightly. (All doors/trunk was closed, key off)

    I tried pulling underhood fuses and even disconnecting the alternator,
    with no result. Then I tried pulling the cabin fuses, and I found that
    it was the Pioneer head unit that was pulling most of the power (for
    the preset memory, I guess).

    When I disconnected the radio, the bulb was finally very dim. I tried
    the ammeter and expected less than 80 mA (from the battery FAQ link,
    thanks to TeGGer). But I still got 170 mA or so. I've checked all the
    possible bulbs, and I think a bulb would pull more than that.

    I finally concluded that there was no parasitic drain at all, but I'm
    puzzled as to what could be making that extra load.
     
    sharx333, Nov 12, 2006
    #9
  10. sharx333

    Earle Horton Guest

    Maybe the Pioneer is wired wrong. It shouldn't take that much current for
    the presets.

    Earle
     
    Earle Horton, Nov 12, 2006
    #10
  11. sharx333

    jim beam Guest

    well, first, you have to eliminate the battery as a problem - if it's
    draining itself, it's no good.

    after that, 170mA is a 2W bulb at 12V [hence bulb glow]. that drain
    seems high for the ecu memory [what you'd have left after disconnecting
    the audio.] i'd continue looking for leakage. check both sets of fuses
    pulling each one individually and connect the meter probes between the
    slots.
     
    jim beam, Nov 12, 2006
    #11
  12. sharx333

    jim beam Guest

    well, first, you have to eliminate the battery as a problem - if it's
    draining itself, it's no good.

    after that, 170mA is a 2W bulb at 12V [hence bulb glow]. that drain
    seems high for the ecu memory [what you'd have left after disconnecting
    the audio.] i'd continue looking for leakage. check both sets of fuses
    pulling each one individually and connect the meter probes between the
    slots.
     
    jim beam, Nov 12, 2006
    #12
  13. sharx333

    sharx333 Guest

    Ok. Thanks for the heads-up.
     
    sharx333, Nov 12, 2006
    #13
  14. sharx333

    sharx333 Guest

    Ok. Thanks for the heads-up.
     
    sharx333, Nov 12, 2006
    #14
  15. sharx333

    dold Guest

    That might be a low wattage lamp, and glow brightly at a low current draw.
    A stoplight bulb is a better choice, perhaps. I could look at autozone.com
    to find the dome light bulb number, and then sylvania.com for the bulb
    specs, but I think you found your culprit.
    I think you are indicating that 170mA made the bulb glow dimly, and the
    Pioneer made it bright. That's not good. The pioneer should only draw a
    few milliamps in standby. There should be a figure in the manual.
    There should also be a standby control on the Pioneer.

    A voltage supplied to the Pioneer that is always on is expected to be a
    heavy current feed for the amplifier, that also draws a tiny amount of
    power in standby. There should be another switched control that comes on
    with the radio or ignition that cause the Pioneer to turn on its
    amplifiers. I think yours is switched on all the time.

    Or maybe not... ;-) Check the manual for some specs on the Pioneer.
     
    dold, Nov 12, 2006
    #15
  16. sharx333

    dold Guest

    That might be a low wattage lamp, and glow brightly at a low current draw.
    A stoplight bulb is a better choice, perhaps. I could look at autozone.com
    to find the dome light bulb number, and then sylvania.com for the bulb
    specs, but I think you found your culprit.
    I think you are indicating that 170mA made the bulb glow dimly, and the
    Pioneer made it bright. That's not good. The pioneer should only draw a
    few milliamps in standby. There should be a figure in the manual.
    There should also be a standby control on the Pioneer.

    A voltage supplied to the Pioneer that is always on is expected to be a
    heavy current feed for the amplifier, that also draws a tiny amount of
    power in standby. There should be another switched control that comes on
    with the radio or ignition that cause the Pioneer to turn on its
    amplifiers. I think yours is switched on all the time.

    Or maybe not... ;-) Check the manual for some specs on the Pioneer.
     
    dold, Nov 12, 2006
    #16
  17. sharx333

    jim beam Guest

    but the 170mA is /after/ the audio is disconnected! yes, the audio
    needs to be addressed, but there's still unusually high residual drain.
     
    jim beam, Nov 12, 2006
    #17
  18. sharx333

    jim beam Guest

    but the 170mA is /after/ the audio is disconnected! yes, the audio
    needs to be addressed, but there's still unusually high residual drain.
     
    jim beam, Nov 12, 2006
    #18
  19. sharx333

    Graham W Guest

    The obvious question is - can you see the Pioneer front panel lit up?
     
    Graham W, Nov 12, 2006
    #19
  20. sharx333

    Graham W Guest

    The obvious question is - can you see the Pioneer front panel lit up?
     
    Graham W, Nov 12, 2006
    #20
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