Porsche 928 ST1991 Owner's Manual page 96

Battery - 1 2 Volt
The battery is located underneath the col-
lapsible spare tire in the luggage compart-
ment. The battery is accessible after taking
out the spare tire.
A replacement battery should always have
the same rating as the original equipment
battery. Specifications are printed on the
battery housing.
Before work is done on the electrical sys-
tem, the battery must be disconnected to
prevent short circuiting. First disconnect
the negative ground wire at body (arrow)
and then the positive cable. To reconnect
battery, reverse the procedure.
This precaution must also be taken be-
fore charging with a rapid charger, as the
alternator may otherwise be damaged.
Disconnecting the battery while the en-
gine is running will damage the alternator.
This also applies to cars equipped with a
battery main switch.
Never drive the car with a disconnected
battery as this will damage the alternator.
If the battery is disconnected, the data for
the engine electronics stored in the control
unit are erased. When the battery is recon-
nected, the engine should be run for approx.
10 minutes to allow the control unit to re-ac-
quire these data. During this period, the en-
gine may idle unevenly or too fast.
WARNING
• Do not lay tools or other metal objects
on the battery as they could cause a
short circuit across the battery terminals.
• Do not expose the battery to an open
flame or electric spark. Hydrogen gas
generated by the battery is explosive.
• Do not let battery acid come in contact
with skin, eyes, fabric or painted sur-
faces.
• If you get electrolyte, which is an acid,
in your eyes or on skin, immediately
rinse with cold water several minutes
and call a doctor.
• Spilled electrolyte must be rinsed off at
once with a solution of water and baking
soda to neutralize the acid and prevent
damage to fabric and metal.
Checking the electrolyte fluid level
The electrolyte fluid level in your battery can
be checked by unscrewing and opening the
filler vent caps of each cell. The fluid level
should meet the indicator mark in each cell.
If necessary, top off with distilled water.
How often water must be added depends on
operating conditions and on the time of year.
Generally, the electrolyte level must be checked
more often in the summer than in the winter,
and more often when driving long distances.
Only fill up to mark, otherwise the electrolyte
will overflow when the battery is being
charged and cause damage.
Battery care
• Battery should be securely mounted.
• Terminals and connections should be
kept clean and properly tightened. Corro-
sion can be prevented by coating termi-
nals and connections with petroleum jelly
or silicone spray.
• Vent caps must be securely tightened to
prevent spillage.
Winter operation
During the winter months, battery capacity
tends to decrease as temperatures drop. Ad-
ditionally, more power is consumed while
starting and the headlights, heater, rear win-
dow defogger, etc., are used more frequently.
Curtail unnecessary power consumption, par-
ticularly in city traffic or when travelling short
distances only. Let your Porsche dealer test
the battery's capacity before winter sets in. A
well charged battery will not only prevent start-
ing problems but will also live longer.
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