Hummer H2. Manual - part 1163

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If the answer is yes, terminal voltage will not be stabilized and you should wait 12 hours since the 
last time the battery was used.  

3. Estimate the battery temperature by determining the average temperature to which the battery has been 

exposed for the past 12 hours. 

4. Measure the battery voltage at the battery terminals. Refer to the following table to determine the SOC 

according to the estimated battery temperature:  

Battery Charging 

Use the SOC information as follows: 

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A battery with a SOC that is below 65 percent must always be recharged before returning it to service or 
continuing storage.  

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A battery with a SOC that is 65 percent or greater is generally considered to be charged enough in order 
to be returned to normal service or in order to continue storage. However, if the battery is being used in 
slow traffic or with short drive times, or if the temperature is very hot or very cold, the battery should be 
fully charged, to at least 90 percent, before returning it to service or continuing storage.  

Charging Time Required 

The time required to charge a battery will vary depending upon the following factors: 

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The battery charger capacity-The higher the charger amperage, the less time it will take to charge the 
battery.  

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The SOC of the battery-A completely discharged battery requires more than twice as much charging time 
as a half charged battery. In a discharged battery with a voltage below 11 volts, the battery has a very 
high internal resistance and may only accept a very low current at first. Later, as the charging current 
causes the acid content to increase in the electrolyte, the charging current will increase. Extremely 
discharged batteries may not activate the reversed voltage protection in some chargers. Refer to the 
manufacturer's instructions for operating this circuitry.  

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The temperature of the battery-The colder the battery is, the more time it takes to recharge the battery. 
The charging current accepted by a cold battery is very low at first. As the battery warms, the charging 
current will increase.  

IMPORTANT: The table is accurate to 10 percent only after the battery has been at rest 

for 12 hours.

Battery Voltage

% Charge at 0° C (32° F)

% Charge at 25° C (75° F)

12.75 V

100%

100%

12.7 V

100%

90%

12.6 V

90%

75%

12.45 V

75%

65%

12.2 V

65%

45%

12.0 V

40%

20%

 

2004 Hummer H2 

2004 ELECTRICAL Engine Electrical - Hummer H2

  

Charging Procedure 

When charging side-terminal batteries with the battery cables connected, connect the charger to the positive 
cable bolt and to a ground located away from the battery. When charging side-terminal batteries with the battery 
cables disconnected, install the battery side terminal adapters and connect the charger to the adapters. 

Tighten: Tighten the battery side terminal adapters to 15 N.m (11 lb ft). 

Use the following procedure to charge the battery: 

1. Turn OFF the charger.  

2. Ensure that all of the battery terminal connections are clean and tight.  

3. Connect the charger positive lead to the battery positive terminal on the battery or the remote jumper stud 

underhood. 

4. Connect the negative charger lead to a solid engine ground or to a ground stud in the engine compartment 

that is connected directly to the battery negative terminal, but away from the battery. If the negative 
battery cable is disconnected and a terminal adapter is being used, connect directly to the adapter.  

5. Turn ON the charger and set to the highest setting for normal charging.  

6. Inspect the battery every half hour after starting the battery charger. 

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Charge the battery until the taper-rate charger indicates that the battery is fully charged.  

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Estimate the battery temperature by feeling the side of the battery. If it feels hot to the touch or its 
temperature is over 45° C (125° F), discontinue charging and allow the battery to cool before 
resuming charging.  

7. After charging, test the battery. Refer to Battery Inspection/Test (Non-HP2) .  

BATTERY ELECTRICAL DRAIN/PARASITIC LOAD TEST (W/BCM) 

Tools Required 

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J 38758 Parasitic Draw Test Switch. See Special Tools and Equipment .  

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J 39200 Digital Multimeter  

Battery Electrical Drain 

NOTE:

Turn OFF the ignition when connecting or disconnecting the battery cables, the 
battery charger or the jumper cables. Failure to do so may damage the PCM or 
other electronic components.

NOTE:

Refer to Fastener Notice in Cautions and Notices.

NOTE:

Do not connect the negative charger lead to the housings of other vehicle 
electrical accessories or equipment. The action of the battery charger may 
damage such equipment.

 

2004 Hummer H2 

2004 ELECTRICAL Engine Electrical - Hummer H2

  

If the vehicle exhibits a low or dead battery after an overnight period, or discharges over a period of 2 or 3 days, 
the electrical system should be checked for an excessive electrical drain. This is referred to as Parasitic Current 
Drain. 

If a battery needs recharging and no cause is evident, check the vehicle for excessive parasitic current drain. 

One or more on-board solid state control modules, such as the body control module (BCM) may at some time 
exhibit a failure mode that causes a high parasitic drain on the vehicle's battery. When the battery is 
disconnected to install an ammeter, etc., the excessive current drain may not occur once the circuit continuity is 
restored. Even though cycling the ignition key to the RUN and then to the OFF position may cause such a drain 
to recur, there may be drains that will not recur unless the vehicle systems are reactivated in a road test. Since 
the ignition switch must not be rotated to the ACCESSORY, RUN or START position with an ammeter 
installed between the battery terminal and the battery cable, a current drain test tool must be used as described 
in the following procedures. 

Before starting this procedure, ensure that the ignition switch is in the LOCK position, all electrical accessories 
are turned OFF, the underhood lamp is disconnected, the door glass is open and the doors are closed. 

1. Disconnect the battery negative cable. Refer to Battery Negative Cable Disconnect/Connect Procedure 

(Single Battery) . 

CAUTION: Refer to Battery Disconnect Caution in Cautions and Notices.

NOTE:

Do not turn the parasitic draw test switch to the OFF position with the engine 
running. Damage will occur to the vehicle's electrical system.

NOTE:

The test switch must be in the ON position when removing the fuses in order to 
maintain continuity in the electrical system. This avoids damaging the digital 
multimeter due to accidental overloading, such as a door being opened to 
change a fuse.

 

2004 Hummer H2 

2004 ELECTRICAL Engine Electrical - Hummer H2

  

Fig. 5: Connecting J 39200 & J 38758 To Battery Cable 
Courtesy of GENERAL MOTORS CORP. 

2. Install the male end of the J 38758 Parasitic Draw Test Switch to the battery negative terminal. See 

Special Tools and Equipment .  

3. Turn OFF the test switch.  

4. Install the battery negative cable to the female end of the test switch.  

5. Turn ON the test switch.  

6. Road test the vehicle while activating all accessories, including the radio and the air conditioning.  

7. Turn OFF the ignition switch. Remove the key. 

IMPORTANT: From this point on, electrical continuity must be maintained in the ground 

circuit of the battery through the J 38758 in the ON position or through 
theJ 39200 . The BCM can draw several amps of current after the ignition 

 

2004 Hummer H2 

2004 ELECTRICAL Engine Electrical - Hummer H2