Page updated on 06-19-2018

battery drain - where and how to fide it

06-13-2006, 06:07 PM
i just got my car about a week ago - its a 2000 impala with 132,000 miles. the battery dies over night and i cant find out where the drain is. the battery will stay charged for at least 5 or 6 hours. i have a reciepe that says the battery was replaced in october of last year. anyone had this problem before or have any ideas?

06-13-2006, 08:31 PM
Hard to tell what is killing the battery, the only way you can check to see what may be draining it, is if you have a voltmeter, and you would have to go fuse by fuse cheacking to see if anything is still sucking power while the car is off.

have you checked all the lights to make sure they arent staying on a bit, even the trunk light?

06-14-2006, 10:12 AM
IF you have a digital multimeter, pull the negative cable off the battery and put your multimeter between the battery and the cable end set to milliamps. Your battery should have an amp hour rating on it. Divide this number by 4, and that is the maximum draw the battery can sustain without going dead overnight. Normal acceptable draw is about 5-8mA (this is due to radio memory, ECM memory, etc...). Start unplugging fuses until the draw drops, and you found the circuit where your problem is. Then you just have to figure out what is causing the draw on that circuit.

06-14-2006, 03:08 PM
The first thing to check is make sure your charging system (alternator) is putting out correctly. With a mulitmeter you should get around 14.5 volts with engine running at idle across the battery positive and negative terminals. With ignition off around 12.0 - 12.5 volts with a properly charged battery. I would get the battery tested to be sure it wasn't defective.

If battery is good you may be getting what is classified as parasitic drain/draw. For a typical Impala the maximum acceptable parasitic load is around 25 - 30 milliamps of current with ignition to off. The battery has a reserve capacity rating on the label. It could be 100 or 120. Divide that figure by 4. So it is either 25 or 30 mA maximum. The lower the better.

When checking drain you must let retained acessory power do its thing after 10 minutes and then test with the multimeter in dc mA after 30 minutes. Typically for most GM "W" body cars to include Impala, 12 - 15 mA is typical.

Items like the BCM module, PCM module, and HVAC circuits will have the highest parasitic load.

06-15-2006, 10:28 AM
I think it is that the battery may have a bad cell

06-15-2006, 02:22 PM
the same thing happen to me. I bought my 2003 Black Chevy Impala and 2 days later the electrical system starts flickering and the power starts going out. So my battery dies and i cant get it to start. So i jumped the battery and it hasnt gone out since. its been running fine. i got it checked out and its @ 10.2v. I dont know why this happened. But i think its because i pressed the acc. while the car was in P and the electrical system was on . thats the last thing i remember doin before it went crazy. Everything is working fine. but i still want to know what caused it. everything is working fine. and btw it has 18K on it.

06-15-2006, 08:09 PM
Disconnect your trunk light, i saw somewhere this problem. Just pull the wire from the bulb. I am gonna check ALLDATA for you, hold on.

06-15-2006, 08:12 PM
CAUTION: Batteries produce explosive gases, contain corrosive acid, and supply levels of electrical current high enough to cause burns. Therefore, to reduce the risk of personal injury when working near a battery (

Always shield your eyes and avoid leaning over the battery ( whenever possible.
Do not expose the battery ( to open flames or sparks.
Do not allow the battery ( electrolyte to contact the eyes or the skin. Flush immediately and thoroughly any contacted areas with water and get medical help.
Follow each step of the jump starting ( procedure in order.
Treat both the booster and the discharged batteries carefully when using the jumper cables.IMPORTANT: Because of the materials used in the manufacture of automotive lead-acid batteries, dealers and service shops that handle them are subject to various regulations issued by OSHA, EPA, DOT, and various state or local agencies. Other regulations may also apply in other locations. Always know and follow these regulations when handling batteries.

Battery Description And Operation
Batteries that are no longer wanted must be disposed of by an approved battery ( recycler and must never be thrown in the trash or sent to a landfill.

Batteries that are not part of the vehicle itself, not the battery ( under the hood, must only be transported on public streets for business purposes via approved hazardous material transportation procedures.

Battery ( storage, charging and testing facilities in repair shops must meet various requirements for ventilation, safety equipment, material segregation, etc.

The maintenance free battery ( is standard. There are no vent plugs in the cover. The battery is completely sealed except for 2 small vent holes in the side. These vent holes allow the small amount of gas that is produced in the battery to escape.

The battery ( has 3 functions as a major source of energy:

Engine cranking
Voltage stabilizer
Alternate source of energy with generator overload Battery Specification Label
The battery ( specification label, example below, contains information about the following:

The test ratings
The original equipment catalog number
The recommended replacement model numberBattery ( Ratings
A battery has 2 ratings:

Reserve capacity
Cold cranking amperageWhen a battery ( is replaced use a battery with similar ratings. Refer to the battery specification label on the original battery or refer to Battery Usage.

Reserve Capacity
Reserve capacity is the amount of time in minutes it takes a fully charged battery (, being discharged at a constant rate of 25 amperes and a constant temperature of 27°C (80°F) to reach a terminal voltage of 10.5 volts . Refer to Battery Usage for the reserve capacity rating of the original equipment battery.

Cold Cranking Amperage
The cold cranking amperage is an indication of the ability of the battery ( to crank the engine at cold temperatures. The cold cranking amperage rating is the minimum amperage the battery must maintain for 30 seconds at -18°C (0°F) while maintaining at least 7.2 volts . Refer to Battery Usage for the cold cranking amperage rating for this vehicle.

06-15-2006, 08:14 PM
This bulletin is being revised to add the 2004 and 2005 model years. Please discard Corporate Bulletin Number 02-06-03-010 (Section 06 - Engine).
In automotive terms, a parasitic drain is an electrical load that draws current from the battery when the ignition is turned off. Some devices, such as the PCM and the radio memory are intended to draw a very small amount continuously. These draws are measured in milliamps (mA).
In normal use, parasitic drains aren't usually cause for concern, because the battery is replenished each time the vehicle is driven. But, in long-term parking situations, parasitic drains may discharge the battery enough to cause a no-start condition. New vehicles in dealer stock and airport long-term parking are two such situations.
An abnormal parasitic drain could be a glovebox or luggage compartment light that remains on but undetected. Or an electronic component may malfunction and cause a parasitic drain that is larger than normal specification.
Parasitic Drains and On-the-Lot Battery Discharge
Important: In most cases of discharged batteries in low-age, low-mileage vehicles, proper charging procedures with approved charging equipment is the only repair necessary.
Here are some rules of thumb that might help relate parasitic drains to how long a battery would last on a parked vehicle. The Reserve Capacity (RC) rating multiplied by 0.6 gives the approximate available ampere-hours (AH) from full charge to complete rundown. Somewhere between full charge and complete rundown, the battery will reach a point at which it can no longer start the engine, although it may still operate some of the electrical accessories.
Using up about 40% of the total available AH will usually take a fully-charged battery to a no-start condition at moderate temperatures of 25°C (77°F). Put another way, for a typical battery in a storage situation, depleting the available AH by 20 to 30 AH will result in a no-start condition.
Important: If the battery begins storage at 90% of full charge, reduce the available AH accordingly.
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.
Here's an example: a vehicle with a 30 mA drain and a fully-charged 70 RC battery will last 23 days. But if that battery is at only 65% of full charge (green dot barely visible), it is going to last only 15 days before causing a no-start.
Effects of Temperature on a Standing Battery
The parasitic drain will be fairly constant over a range of temperatures. The important temperature is that of the vehicle at the time a start is attempted. Colder temperature raises the threshold of a no-start by increasing the residual power needed. When the temperature falls to 0°C (32°F), the battery will be able to put out only about 85% of its normally available starting power, and the engine may need as much as 165% of the usual power to start.
The combined effect of these two factors is to reduce the number of days the battery can stand with a parasitic drain. At 0°C (32°F), the battery can stand only half as long as it could at 25°C (77°F). And at -19°C (0°F), the standing days are reduced to one-fourth.
Temperatures above the moderate climate of 25°C (77°F) increase the battery's internal self discharge. If the battery is in a locale where the temperature is averaging 32°C (90°F), an additional 5% to 10% of the available ampere-hours will be lost in a month due to self-discharge within the battery. At temperatures below the moderate range, self-discharge will be low enough to be negligible compared to the parasitic loss.
What the Policies and Procedures Manual Says About Parasitic Drains
Because determining how long a battery may last in a storage situation is not precise, the P & P manual provides a clear-cut policy, excerpted here.
"Discharged batteries can freeze at temperatures as high as 0°C (32°F), causing permanent damage. Other permanent damage may result from allowing batteries to stand discharged for extended periods."
"To alleviate this condition, the negative battery cable ( should be disconnected on vehicles which are not going to be in service within a 20 day period, beginning from the time the vehicle is shipped. If this is not possible, batteries should be recharged periodically, every 20-45 days, until the green eye is visible."
"Disconnected batteries will slowly discharge, especially with higher temperatures; therefore, even disconnected batteries should be checked every four months and recharged if necessary."
"Vehicles on display are subject to battery discharge due to drains from courtesy lights and other accessories. Provision to maintain battery state of charge for these vehicles will be necessary."
Consult your P & P manual for full details.
Tracking Down the Source of a Parasitic Load
If the battery in a vehicle becomes discharged in a shorter time than described earlier, the vehicle may have an out-of-specification parasitic load. Refer to Service Information (SI) for procedures for locating parasitic drains. Follow these steps:
1.Build the vehicle.
2.Select the Engine section.
3.Select the Engine Electrical sub-section.
4.Select Diagnostic Information and Procedures.
5.Select Battery Electrical Drain/Parasitic Load Test.
You will need the J 38758 Parasitic Draw Test Switch and a digital multimeter set to the 10A scale.
Important: Read the procedure and follow the steps exactly as described in SI. The following is a summary, not the complete procedure.
The test switch permits you to place an ammeter in series with the battery negative cable. Before performing the test, the engine must be run and all accessories must be operated as instructed. After shutting the ignition off, turn the test switch off. Now, all the current being used by the vehicle is shunted through the ammeter where it is measured. If the reading is out of specification, the procedure explains how to pinpoint the cause.
A Final Word About Battery Testing
Your dealership has an essential tool, the Midtronics Micro 410 Battery Tester, J 42000. Use it to quickly identify batteries that are serviceable and can be charged. Refer to Corporate Bulletin Number 02-06-03-006A for more information about this tool.

Add your comment to this topic!