Mazda mx5 Owner's Manual page 480

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).
Booster battery
7–22
CAUTION
Jumper leads
Discharged battery