A precautionary message in your car owner's manual or on top of your battery tells how to connect jumper cables safely to prevent sparks and a possible explosion. An additional statement might warn about the dangers of using substandard quality jumper cables. These can produce a situation similar to connecting a thin, poorly insulated extension cord to an electric heater. The wire could heat up, eventually melting the insulation and causing a short circuit. In household wiring a fuse or circuit breaker probably would prevent a fire. In the case of jumper cables, where there is no circuit breaker protection, inadequate strands of wiring, leading to melted insulation, could be a real hazard.

Among other shortcomings of inferior booster cables include:

• High resistance in inferior cables can damage the starter motor when subjected to long periods of cranking.
• Flimsy, poorly insulated clamps with weak springs can provide poor electrical connections.
• Poor quality cable jackets (insulation) become excessively stiff in freezing weather.

The engineers of Associated Equipment Corporation offer tips on features to look for:

• Built in warning lights to signal incorrect connection.
• Flexible cable guards at the clamp handle to prevent wear at stress points.
• Pure copper wire in the cables for best conductivity.
• Adequate length and gauge of cable (12 - 16 ft; 4 gauge).
• Tangle-free design with a heavy duty insulated jacket.
• Clamps covered with bonded vinyl insulation.
• Insulated clamp jaw with no exposed metal parts which could arc when contacting vehicle frame or other parts.
• Clamps should fit both top or side terminal batteries.