Larger portable jump-starting devices that clamp to a car's battery have become common in the past few years. But even smaller devices, which plug into a car's power outlet, are now on the market.
These devices, which cost between $20 and $50, do not instantly start your car. They take 5 to 10 minutes to charge your battery when it's low. But our testing in four vehicles of various sizes with drained batteries showed that only two of four portable jumpers, the Black & Decker Simple Start, $40, and the Schumacher e-Charge EC-4000, $50, worked on all the vehicles. All models were fully charged before each test.
These models have lead-acid batteries that can be recharged and used again. But they must be periodically recharged even if they're not used because they lose their charge over time.
They're also larger and weigh more than 4 pounds, so you'd probably want to store them in the trunk. Five of nine Schumacher batteries started our test vehicles, but two of them required additional charging beyond the manufacturer's instructions. Four appeared to come with dead internal batteries and weren't able to start our test cars even with additional charging.
We also tested the StartMeUp2, $20, and the Porta-Jump PJR-STH, $30, which are lighter in weight and small enough to fit in most glove compartments.
The StartMeUp2 needs no maintenance. But it contains a nonrechargeable battery that is good for just one use. Both models started only one of our vehicles.
Bottom line. If you want a portable model, the Black & Decker is the only one worth a try. But be sure to keep it charged. Your best bet is to buy a set of booster cables at least 12 feet long and between 4 and 6 gauge. They don't need maintenance, and as long as you have access to a second vehicle, they can be used to jump-start any car.