Intrinisic current drain on battery

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Mikel65, Oct 26, 2013.

  1. Mikel65

    Mikel65 New Member

    I have a '94 Silverado 5.7 that will drain the battery if it sits for more than a week when we take trips in our other vehicle. The battery has been charged, loaded tested and is good with only 30 months of a 72 month warranty life. I have hooked an ammeter in series with the battery and have a 8.75 milliamp constant drain. Hood, courtesy, glove box and brake lights (upper and tail) have been removed and no change. I have pulled each fuse, breaker and the flashers under the dash (left side) and the only change is with the panel lights fuse and it drops the drain to 6.0 milliamps. Not significant but a variance.
    My two questions are: (1) Is there an acceptable intrinsic current drain on the battery with digital components. I assume the small panel current draw is from the digital clock which is required to stay accurate. (2) Where is the underhood fuse and relay panel located. Since I pulled all the under dash fuses/breakers with no change, I am thinking maybe I have a corrosive/high resistance short under the hood. My manual says it is connected to the positive battery cable but those leads only go to the alternator, starter and starter solenoid. I cannot find this panel. Any help would be appreciated. Thanks, in advance. Mike L
  2. Conlan Rose

    Conlan Rose Epic Member 5+ Years 1000 Posts

    There is a black peice of plastic next to the coolant recovery bottle. Behind it is a whole bunch of positive leads from the battery.
  3. j cat

    j cat Epic Member 5+ Years 1000 Posts

    the 8 MA drain is not high. 200ma-50 ma is considered normal on newer vehicles.

    I would remove and clean all battery power/ground connections ....check for green wiring. any wires green should be replaced. make sure the battery tray holds the battery securely.

    when it does not start measure the voltage across the battery posts when cranking . if the battery volts does not drop much but you get a weak or no crank then you have connection issues. also poor connections will cause the battery not to charge properly.
  4. Mikel65

    Mikel65 New Member

    Thanks for the info Conlan. I had already found these terminals, but still no obvious feed to the underhood fuse panel. I will keep looking. Maybe it is hidden under the dash on the passenger side. Thanks again for the reply. Mike L

    - - - Updated - - -

    j cat. Thanks for that info. To me, 50ma or more seems excessive. If the car sits dormant for for 7-10 days, that should be enough to drop the capacity of the battery below expected norms. I may be wrong, but I believe 50-200 microamps would be norm. Can you clarify your estimations? The battery voltage is low after it sits. I have previously cleaned the battery terminals and there is no corrosion on them or the alternator. I have not pulled the starter leads as of yet (ackward access) but I am still looking for the underhood fuse and relay panel which has "always hot" circuits. If you know where that is, that might help. In any case, thanks for the reply and input. Later, Mike L
  5. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Mike, I suspect you need to find the under-hood battery terminal and start pulling those fuses.

    You sound like you have some electrical experience, so you probably know that a load (even a small on) is going to eventually drain the battery; dirty/corroded connections will not drain a battery. Dirty connections will prevent current flow, not drain a battery.

    I don't have a manual for your truck, so I don't know where the fuses are, but, tracing a large red battery lead should get you there. It is usually a flat black box, maybe 6" by 8".
  6. j cat

    j cat Epic Member 5+ Years 1000 Posts

    on your specific vehicle this drain of 8 MA should cause no problems with the battery over a week.

    the drain may be due to the PCM as it is always on. another item with battery drain issues would be any alarms and other aftermarket devices.

    put the head lights on for a few minutes and then crank the engine what does the voltage read [AT BATTERY POSTS]while cranking ?

    this is from a TSB for 2003-6 trucks silverado ;

    The recommendation for maximum parasitic drain is around 30 mA (0.030 amp). A typical drain today actually falls into the 7-12 mA range, even though some vehicles do approach the maximum. Multiply the drain (in amps) by the time (in hours) the battery sits without being recharged. The result is the amount of AH consumed by the parasitic drain. The actual drain may be small, but over time the battery grows steadily weaker.

    what battery do you have ? who made it ? CCAMPS ?
    Last edited: Oct 27, 2013

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