911 Carrera Coupe F6-3164cc 3.2L (1984)
Technical Service Bulletin # 29204
Date: 920929
Battery - Diagnosing a Discharging Condition
September 29, 1992
Model
All
Part Identifier
2706
Group
2
Number
9204
Subject:
Battery Discharging
ATTENTION:
Service Manager/Service Technician
Models Affected:
All
Concern:
Servicing Batteries: Battery testing and constant current draw checking procedures.
Bulletin Contents:
Our experience and information from dealers show very different methods and opinions about battery service and testing. To address this subject in
detail, additional information, recommendations and suggestions are given in the following text.
The following subjects are addressed in this technical bulletin.
1.
General information.
2.
Battery service (general/new, stored and displayed vehicles).
3.
Hints on vehicle delivery.
4.
Replacement batteries.
5.
Discharged batteries.
6.
Voltage and electrolyte density checking (correction values).
7.
Load testing.
8.
Current draw checking.
9.
Summary.
1. General Information
The condition of a battery can be determined by measuring battery voltage (or electrolyte density) and battery load testing.
Battery voltage or electrolyte density gives information about the charging condition. (Energy stored through electro-chemical transformation.) 100%
charging condition with all cells OK corresponds to 12.7 volts or 1.28 g/ml, acid density.
Starting capability of a battery is the characteristic to release stored energy under load. This capability decreases with discharge, eventually sulfating with
age.
Battery wear is very high when discharging and charging often (high cyclic load), for instance short distance driving, demonstrator vehicle service or at
high ambient temperatures.
General assumption: New Battery = Full Battery. In storage, a battery discharges through self-discharge (up to 1 % of A(h) capacity per day). If the
battery is installed in a vehicle, current draw and temperature are additional influences.
Long transportation, handling and parking times of the vehicle are also influencing factors. Measures are taken on all vehicles at the factory to reduce
current draw during transportation.
Other influencing conditions are traffic density, speed limits and personal driving habits.