Questions and Answers

Dodge Grand Caravan Overcharging? Q. Just put in a new battery, and with the engine running my voltmeter indicates 14.50 to 14.55 volts DC. After reading that 13.5 to 14.5 volts DC is the limits for most charging systems I was concerned that it was staying at 14.50. I have a cheap pocket cigarette lighter voltage checker that indicates that it is slightly overcharging and reads normal on my other cars.

Like I said it is cheap, but just wondering about that voltage staying at 14.50 volts DC. Prior to putting in the new battery I put a fully automatic 1.5 amp trickle charger on it to make sure it was fully charged prior to installing. For my make and model Caravan and having just put in a new battery is it normal for it to run at 14.50 volts DC for a while and then will it settle down from there or is that about normal for my model and year Caravan?

• 1991 Dodge Grand Caravan SE
• 3.3 liter
• Automatic transmission
• 111,456 miles
• P/S, A/C, Cruise control

Thanks,
Chuck
Minot, North Dakota

A. Voltage regulation is necessary on all vehicles that have a charging system with an alternator. All voltage regulators limit the voltage the vehicle's charging system produces. The need for this regulation is most critical on vehicles with electronic devices, such as an Powertrain Control Module (PCM), body controller, or ETR radio. Inconsistent voltage levels or excessively high or low voltage levels have a negative effect on the performance and durability of electronic components.

There are two basic functions of a voltage regulator:

1. To maintain a constant system voltage regardless of the vehicle's electrical load requirements or its engine speed.
2. To regulate system voltage to keep the battery at an optimum state of charge.

Specifically for Chrysler, the Powertrain Control Module (PCM) contains the voltage regulator function. The PCM uses the battery voltage sense, the battery temperature sensor, and its own program to determine the charging system's voltage goal. The voltage goal is adjusted by the controller based on changes in the voltage sense and temperature values.

The basic voltage regulating function is to keep the charging system voltage between 12.9 and 15.0 volts. The voltage regulator accomplishes this by controlling the current flow through the rotor. Since the rotor is electromagnetic, controlling the current through the rotor effectively limits the strength of the magnetic field and the output of the alternator.

BATTERY VOLTAGE SENSE:
The battery voltage sense is the sensor value that establishes the basic charging rate of the alternator. The voltage level sensed is used by the PCM to determine the vehicle's electrical load condition and the battery's state of charge.

The PCM controls the alternator's field ground based on how close the battery sense voltage is to the voltage goal. If the battery sense voltage is below the voltage goal, the PCM initiates the grounding of the field. If the battery sense voltage is above the voltage goal, the module stops grounding the field, thus effectively disabling the magnet and stopping output.

BATTERY TEMPERATURE SENSOR:
The battery temperature sensor signal is a voltage used by the PCM to report the temperature under the hood. This temperature is used to indicate the battery temperature. The battery's temperature is critical to its state of charge and to determining the charging rate.

Since you are within the 12.9 and 15.0 volts that Chrysler wants, I would say you have no problems. However, you may want to check, or replace, the battery temperature sensor to make sure it is reading accurately.