They can provide dozens of jump-starts to get you to work, then tag along on vacations to deliver hours of power to a cellular phone, laptop computer or portable television. The main role of power packs is as a battery booster. They provide a simple way to jump-start a dead engine when no other help is at hand. It's like carrying a spare battery, but with added features and convenience. Most use new battery technology that fills the cells with fiberglass material to absorb the acid.
Excess fluid is drained off, and the battery is sealed in a handy carrying case.
It's a great technique that results in a battery with more power than regular, though the cost is higher. When they are available, the latter two ratings are the most telling. A battery's reserve capacity is indicated by its amp-hour size. Power packs are typically equipped with 12 to 18 amp-hour batteries. Depending on the quality of those batteries, power to jump-start from 20 to 50 engines is available.