Mercedes-Benz GLA 250 2019 Operator's Manual page 298

Jump-starting
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WARNING
During the charging process, a battery produces hydrogen gas. If a short circuit occurs or
sparks are created, the hydrogen gas can ignite. There is a risk of an explosion.
Make sure that the positive terminal of a connected battery does not come into contact with
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vehicle parts.
Never place metal objects or tools on a battery.
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It is important that you observe the described order of the battery terminals when connect-
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ing and disconnecting a battery.
When jump-starting, make sure that the battery poles with identical polarity are connected.
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It is particularly important to observe the described order when connecting and disconnect-
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ing the jumper cables.
Never connect or disconnect the battery terminals while the engine is running.
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WARNING
A discharged battery can freeze at temperatures below freezing point. When jump-starting the
vehicle or charging the battery, gases can escape from the battery. There is a risk of an explo-
sion.
Allow the frozen battery to thaw out before charging it or jump-starting.
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Avoid repeated and lengthy starting attempts. Otherwise, the catalytic converter could be
damaged by the non-combusted fuel.
If the indicator/warning lamps do not light up in the instrument cluster at low temperatures, it is
very likely that the discharged battery has frozen. In this case you may neither jump-start the
vehicle nor charge the battery. Let the battery thaw first. The service life of a thawed-out battery
may be shorter. The starting characteristics can be impaired, particularly at low temperatures.
Have the thawed-out battery checked at a qualified specialist workshop.
Do not start the vehicle using a rapid charging device. If your vehicle's battery is discharged, the
engine can be jump-started from another vehicle or from a second battery using jumper cables.
Observe the following points:
The battery is not accessible in all vehicles. If the other vehicle's battery is not accessible,
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jump-start the vehicle using a second battery or a jump-starting device.
You may only jump-start the vehicle when the engine and exhaust system are cold.
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Do not start the engine if the battery is frozen. Let the battery thaw first.
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Only jump-start from batteries with a 12 V voltage rating.
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Only use jumper cables that are not damaged and have a sufficient cross-section and insula-
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ted terminal clamps.
Make sure that the two vehicles do not touch.
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Make sure that:
The jumper cables are not damaged.
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Non-insulated parts of the terminal clamps do not come into contact with other metal parts
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while the jumper cables are connected to the battery.
The jumper cables cannot come into contact with parts that can move when the engine is run-
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ning, such as the V-belt pulley or the fan.
Secure the vehicle by applying the electric parking brake.
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Shift the transmission to position j.
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Turn the SmartKey to position g in the ignition lock and remove it.
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