Home » GM 6.5 » GM/Detroit 6.5L – BATTERY CHARGING


Refer to Figures 2, 3» 4, and 5
When it is necessary to charge the battery, the follow­ing basic rules must be followed (figure 3):
1. Use a charger with an end of charge voltage of 16.0 volts and equipped with a voltmeter that is accurate within 1 percent.
2. Ambient (surrounding) temperature should be 15° C to 38’ C (60° F to 100° F). A battery that is extremely cold may not accept measurable current for several hours after starting the charger.
3. Charging area should be well ventilated.
4. Do not charge the battery if the built-in hydrometer is clear or light yellow. If cranking problems exist, replace the battery.

5. Do not charge a battery if it seems to be frozen.
Replace it.
6. Batteries with a green dot showing in the hydrome­ter do not require charging unless they have just been discharged (such as cranking the vehicle).


CAUTION: Always turn o ff the ignition switch when connecting or disconnecting battery cables, battery chargers, or jum per cables. Failure to do so may result in personal injury and damage to the powertrain control module or other electronic components.

When charging the battery in the vehicle, proceed to
step 1. If charging side terminal batteries out of the
vehicle, install an adapter kit (GM P/N 12303040 or
equivalent) (figure 5).
The adapters should be tightened against the lead
terminals of the battery to keep resistance between the
adapter and the battery terminals to a minimum.
1. Make sure all charger connections are clean and
2. Charge the battery using the charger setting for
12-volt batteries that gives the highest charge rate
to the battery until the green dot appears. (Do not
use charger settings for jump-starting vehicles to
charge the battery. Refer to the charger manufac­
turer’s instructions). The battery should be checked
periodically while charging. Tap the hydrometer
lightly on the top to dislodge any air bubbles that
may prevent a correct indication.
3. If the battery feels hot 52“ C (125° F), or if violent
gassing or spewing of electrolyte through the vent
holes occurs, discontinue charging or reduce the
charging rate.
4. After charging, the battery should be tested as out­ lined in “ Diagnosis of the Battery.”

The time required to charge a battery will vary depending upon the following factors;
A. Size of the Battery – A completely discharged heavy-duty battery requires more than twice the recharging time as a com pletely discharged light-duty battery.
B. Temperature – The colder the battery, the more time it takes to recharge. When a fast charger is connected to a cold battery, the current accepted by the battery will be very low at first. In time the battery will accept a higher rate as the battery warms.
C. Charger Capacity – The higher the charger amper­age, the less time it will take to charge the battery.
D. State-Of-Charge – A completely discharged battery requires more than twice as much charge as a one-half charged battery. Because the electrolyte is nearly pure water and a poor conductor in a com­pletely discharged battery, the current accepted by the battery is very low at first. Later, as the charg­ing current causes the electrolyte acid content to increase, charging current will also increase.

Any battery discharged by parasitic current drain, and then allowed to stand in this condition for a period of time, may not accept a charge readily. However, if recharged long enough, many batteries will return to a usable condition.

If the battery remains in an extremely discharged con­dition for a prolonged period, it can become permanent­ly damaged. This damage can be accelerated by changes in temperatures. Batteries that are extremely discharged can freeze at temperatures as high as -7° C (20° F) and be permanently damaged.

To prevent battery damage and recharge problems, vehicles that are not going to be in service within a 30 day period should have the negative battery cable dis­connected to remove the constant drain on the battery. If this is not possible, recharge the battery periodically every 30-45 days until the green dot is visible.



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