Beating the dead-battery blues.(portable battery boosters)(Auto Parts)(Evaluation)

A car battery can go dead at any time, often without warning. Batteries can become discharged because of lack of use, a defective charging system, or something as simple as a light being left on in the car. In recent years, a number of portable battery boosters have been introduced that allow you to jump-start a car's battery without needing separate jumper cables or a second vehicle.

Standard-sized boosters are about the size of a pocketbook and weigh 12 to 19 pounds. Compact models are lighter and take up less space. In addition to being able to crank a car engine (or a lawn tractor or a motorboat), many models have an outlet for running a DC-powered appliance, such as a portable air compressor or electric picnic cooler, or for powering or recharging a cellular phone. With an optional AC inverter, a booster can power a radio, laptop computer, or television set--handy in the wilds or in a power blackout at home.

We tested four standard models, costing $79 to $99, and two compact units, priced at $60 and $79. They were purchased at mass merchandisers such as Wal-Mart and warehouse clubs, and online. Using laboratory battery-test gear, we ran a series of cranking-performance tests at a moderate temperature (75[degree]F) and after chilling the units to zero degrees. We simulated cranking an engine until the units ran down and used them, both warm and chilled, to start a car that had a run-down battery.

All of the models we tested will start a car in moderate temperatures. Better ones can provide more starts per charge and are more likely to start a vehicle with a deeply discharged battery or a mechanical problem that requires excessive cranking. All of the ones we tested suffered reduced performance after being stored at zero degrees.

The best we tested was the Century Booster Pac J900 (Century has since been bought by Clore Automotive). It proved very capable, warm or cold, and provided far more starts per charge than any other unit. Like several other models, it has "smart" recharging--you can leave it plugged in without overcharging it. Its $79 price makes it A CR Best ...