Christie Automotive offers their CS 3 Smart Starter booster cart that can charge up to 30 cars without re-charging the booster battery. Features include: A red warning light that indicates a reversed or incorrect connection. A built-in automatic charger that maintains charge when the unit is not in use. A low battery light that indicates when the booster battery needs to be recharged. Christie's spike voltage and automatic reverse polarity protection to help prevent damage to vehicle computer electronic systems from voltage spikes or surges and reverse boosting. Larger 500-amp vinyl coated clamps and heavier cable to better handle colder weather. A vehicle battery voltmeter to help diagnose probable starting problems, such as bad cables, connections or starter motor failures. AC input power of 120 volts AC; DC output power of 12 volts DC.