Mazda 3 Owner's Manual page 580

If Trouble Arises
Battery Runs Out
Use only a 12 V booster system. You can damage a 12 V starter, ignition system, and other
electrical parts beyond repair with a 24 V power supply (two 12 V batteries in series or a
24 V motor generator set).
Connect leads in numerical order and disconnect in reverse order.
1. Remove the battery cover.
2. Make sure the booster battery is 12
V and that its negative terminal is
grounded.
7–22
CAUTION
Jumper leads
Booster battery
Discharged battery
3. If the booster battery is in another
vehicle, do not allow both vehicles
to touch. Turn off the engine of the
vehicle with the booster battery and
all unnecessary electrical loads in both
vehicles.
4. Connect the jumper leads in the exact
sequence as in the illustration.
Connect one end of a lead to the
positive terminal on the discharged
battery (1).
Attach the other end to the positive
terminal on the booster battery (2).
Connect one end of the other lead to
the negative terminal of the booster
battery (3).
Connect the other end to the ground
point indicated in the illustration away
from the discharged battery (4).