Service Bulletin

Bulletin No.: 15-06-03-001F
Date: March, 2025

INFORMATION
Subject:

Cold Weather and Long Stand Time Battery Maintenance and Testing Tips

Models:

2026 and Prior GM Passenger Cars and Trucks (includes Medium Duty)

Attention:

This Bulletin also applies to any of the above models that may be Export
from North America vehicles.

This bulletin has been revised to add the 2020-2026 Model Years and first Important
statement. Please discard Corporate Bulletin Number 15-06-03-001E.
Important: Service agents must comply with all International, Federal, State, Provincial, and/or Local laws
applicable to the activities it performs under this bulletin, including but not limited to handling, deploying,
preparing, classifying, packaging, marking, labeling, and shipping dangerous goods. In the event of a
conflict between the procedures set forth in this bulletin and the laws that apply to your dealership, you
must follow those applicable laws.
The following diagnosis might be helpful if the vehicle exhibits symptom(s), that include but not limited to, a slow or
no crank condition that may be caused by a discharged battery.
Below is information that may be useful on diagnosing batteries that have set for a long period of time and/or set in
cold weather climates and testing those batteries.
Effects of Long Stand Time

4052173

(1) = Normal Battery
(2) = Stratified Battery

Copyright 2025 General Motors. All Rights Reserved.

Page 2

March, 2025

Bulletin No.: 15-06-03-001F

Inside the battery, the electrolyte is generally composed of 35% Sulfuric Acid and 65% water. When a lead acid
battery is inactive (not actively discharged and charged), the acid, being heavier than water, will settle toward the
bottom. This leaves a low acid concentration near the top, and higher concentration at the bottom, this condition is
referred to as acid stratification (Figure 1). Since it is the concentration of the sulfuric acid that lowers the electrolyte
freeze point, the upper levels of the acid (with low acid concentration) in this state can begin freezing at or near 0°C
(32°F).
Note: Stratification does not affect AGM type batteries.

4052174

(1) = Acid density is high.
(2) = Acid density is low.
(3) = Acid density is not distributed evenly.
In a low state of charge (SOC), lead sulfate will form on the battery plates. This creates what is known as the
“Sulfated Battery” condition. The lead sulfate insulates the plate’s reactive material, which reduces capacity and
decreases the battery’s ability to accept a charge. Sulfation begins to occur below 80% state of charge in as little as
two weeks. The longer the battery is left in a low state of charge, the more lead sulfate forms. Batteries that have
been deeply discharged for periods longer than 60 days may be permanently damaged.
Note: Long stand time causes sulfation, which may result in customer no start events due to reduced battery
capacity. Thus, it is imperative to maintain (charge) the battery every 30 days to ensure the battery state of charge
(SOC) remains greater than 80%.
Notice: Batteries that are deeply discharged will take an extended time to recharge. Batteries that are cold
(below freezing) can falsely fail testing. Batteries that are cold and deeply discharged must first be warmed
prior to testing & charging.
Cold Battery Testing – Battery Temperature at Less Than 0°C (32°F)
When an automotive 12 Volt battery is cold, (below freezing) its capacity starts to reduce. This can be observed in
the voltage level of the battery, as well as measured cold cranking amps. A cold battery is also resistant to charging.
The colder the battery, the more these characteristics are affected.
Depending how cold a battery is, it can fail testing using any type of battery test equipment, including the EL-50313
(GR8).
Important: It is impossible to calculate the core temperature of a battery, so using external surface temperature is
not reliable. Warm the battery a minimum of 12 hours prior to testing. Longer warming times will be needed
depending how cold the battery is.

Bulletin No.: 15-06-03-001F

March, 2025

Page 3

Note: Cold batteries are resistant to charging even when in use on the vehicle. They will not recover quickly in
subfreezing temperatures. Releasing a new vehicle with a battery in a low state of charge puts the customer at risk
to a no crank event.
Battery Charging and Testing Tips
The majority of these tips apply to new vehicles in inventory or relatively new batteries (less than 12 months old).
Batteries tend to recharge in the same manner as they were discharged and temperature affects charge time:
• Cold Battery = Slow Recharge
• Slow Discharge = Slow Recharge
• Fast Discharge = Fast Recharge
Note: If you suspect that a battery may be frozen, inspect the case for cracks prior to charging. Do not charge a
frozen battery.
Always warm a cold battery temperature to above 4°C (40°F) prior to testing.
The EL-50313 (GR8) has a built in algorithm to limit the length of time needed to recharge a battery. Because cold
batteries are resistant to charge, or it is deeply discharged, it may calculate longer than reasonable time to recover
the battery and fail it. If you are working with a newer battery that is most likely simply discharged, select Manual
Charge, Limit Current, 10 Amps, for 120 Minutes. Once that is complete, perform another Diagnostic Charge.
Note: AGM batteries are sensitive to overcharging. Maximum charging voltage should be limited to 14.5V.
Caution: Do not continue charging when battery temperatures are above 49°C (120°F).
If a newer battery fails testing, allow it to rest overnight and retest. It will often “soak” in the charge and test good
after a 12–24 hour rest.
Note: If the tool responds with “Unsafe to Charge” or “Shorted Cell” message do not proceed.
Correct battery cold cranking amperage (CCA) ratings and type are critical for proper test results when using the
EL-50313. Access to the battery specification label which contains the CCA rating and type may be difficult without
component removal. Refer to the latest version of PI1098 Battery Test Cold Cranking Amperage (CCA) for Original
Equipment Batteries and Testing Tips in SI.
Absorbent Glass Mat (AGM) Battery
Many GM vehicles are now equipped with a 12 Volt Absorbent Glass Mat (AGM) battery.
This battery is similar to current vehicle lead acid flood batteries, except it uses glass mats that absorb electrolytes
that are pressed between the plates instead of immersing the plates in electrolytes. This allows for a smaller, lighter
battery with the same amount of power that is less susceptible to heat. The maximum permissible voltage allowed
for the absorbent glass mat battery is 14.5 Volts at room temperature.
The AGM battery requires different charging voltages than conventional lead acid batteries. The essential tool
EL-50313 Midtronics® GR8 Battery Charger/Tester has this algorithm built in. The EL-50313 Midtronics® GR8
Battery Charger/Tester is the preferred charger for use during a PDI, calibration updates or any other repairs that
requires the use of a battery charger. You MUST select AGM when prompted or damage to the battery will result.
Make sure to select the proper battery type: AGM and CCA during charger set up. Incorrectly selecting "flooded"
battery may cause unnecessary battery replacements.
Refer to the latest version of Bulletin 15-06-03-002 in SI for battery type and CCA rating if the battery label is
unavailable.
Storage Tip
Transport Mode – This is designed to help vehicles that are not being used (In Transport or Storage) use less battery
energy. Vehicles with this feature are generally shipped from assembly with this mode on. While in inventory we
recommend that this feature be on. Refer to the latest version of Bulletin 11-08-49-001 for instructions on how to turn
the mode on/off.
If you need additional information regarding warranty coverage, please review GM Service P&P Manual, Article 2.8.1
- Battery Charge and Test” and “GM Transportation, Vehicle Storage and PDI Policy Manual, Article 2.1.2(b) Battery Care.” This is also outlined in the latest version of Bulletin 03-06-03-004.

Page 4

March, 2025

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job
properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.

Bulletin No.: 15-06-03-001F

WE SUPPORT VOLUNTARY
TECHNICIAN
CERTIFICATION