Porsche 928S 1983 Driver Manual page 78

Battery check and care
Because of the danger of short circuiting,
the battery should always be disconnected
before starting any work on the electrical
system. Disconnect the battery earth strap
as shown by the arrow in the picture.
Disconnecting the battery
engine is running destroys the alternator.
This applies also to vehicles with a built in
battery disconnection switch.
Remember that only a well charged battery
can deliver the necessary energy to start the
engine. The condition of the battery should
therefore be checked regularly. The battery
is located in the back of the vehicle, and is
reached via a flap in the spare wheel well.
Before the battery is to be charged with a
heavy duty charger, it must be disconnec-
ted, or otherwise the alternator can be de-
stroyed.
The battery capacity is reduced by lower
temperatures. However, during the winter
months, the demands made upon the bat-
tery increase because of the need for more
lighting, heating fan, windscreen wipers etc.
Therefore check, especially when only mak-
ing short journeys, that all unnecessary elec-
trical systems are turned off.
76
Checking the acid level
With the vehicle standing level, remove all
the battery stoppers, and check that the
acid level in every cell reaches the full mark.
If the battery has to be topped up, use only
distilled water, not acid. During the summer
months, and in warmer climates, the battery
level should be checked more often.
whilst the
Checking the specific gravity of the acid
In a battery in good condition, the state of
charge of the battery can be determined by
the specific gravity of the acid, which is mea-
sured in Kg/dm
hydrometer.
Checking the voltage of the battery
The voltage of a battery can only be measured
with a special instrument, and should there-
fore be left to an authorized workshop.
Care of the battery
The battery poles must be kept clean. They
should be smeared with a suitable grease,
and check that the battery terminals are pro-
perly fitted.
Check that the battery stoppers are seated
correctly, and that the vent holes in them are
not blocked.
Never let any acid come into contact with
clothing, or any parts of the vehicle. Should
3
, determined with the use of a
battery acid be splashed or spilled, it should
be immediately neutralised with a soda solu-
tion.
Due to the explosive gases given off by a
battery, never go near it with a naked flame
or fire.
A battery loses it's charge when not being
used, so if the vehicle is laid up for any
period, the battery should be charged ap-
prox. every 6 weeks, to keep it in good con-
dition. A battery left discharged for a length
of time will be ruined. Check, and if neces-
sary top up the acid level, every time the bat-
tery is charged.