How Do Jump Starters Work?

You've probably been there: finally done after a few hours of errands or just getting back from a long trip, you find your vehicle in the parking lot. You climb into the driver's seat and try to start the engine – only to find that it won’t turn over. Whether it's an old battery or you accidentally left the lights on while you were away, a dead battery can ruin your day. Automotive safety experts recommend always carrying jumper cables in your car, but that doesn't do you much good if there isn't another person around to give you a jump. Carrying a portable jump starter, like the Cobra Jump Starter 800A or 1000A, can get you back on the road quickly and safely. They allow you to start your vehicle without having to call and wait for roadside assistance to come to you or ask a passerby to help jump start your vehicle.

Jump starters work by using a special high current Lithium-Ion battery to provide enough power to start your engine. These batteries are rechargeable, and newer products should be able to not need a recharge for over a year (unless they’ve been used multiple times). They can often jump start multiple vehicles on one charge and some models can even act as a portable power bank to charge and power your devices like smartphones or tablets. Most portable jump starters are designed to be able to easily start a drained battery in gasoline and diesel-powered passenger cars and light-duty trucks that won't start because of cold temperatures, the lights were left on, or they haven't been driven for a while.

How to Use a Jump Starter

How you use a portable jump starter will depend on the model, and you should always read and follow all manufacturer instructions to start a vehicle safely and effectively. The instructions provided here are from the Cobra Jump Starter 800A and 1000A mentioned above, and are typical for most battery-powered jump starters, but always check your product manual before using any device.

How to jump start your vehicle using the direct-to-battery method

1. Connect the jumper cable clamps to the battery terminals (first Red to Positive, then Black to Negative )
2. Connect the jumper cable to the jump starter
3. Wait for the green LED on the jumper cable to light up and then start your vehicle
4. Disconnect the jumper cable from the jump starter and then from the battery in reverse order

Note that if the vehicle does not start after several attempts, your jump starter may stop working (or go into "recovery mode") to prevent the battery from overheating. This may happen if the vehicle battery is too far drained to be able to be jump started.

How to jump start your vehicle from inside the car

Some jump starters – including the Cobra Jump Starter 1000A – can be safely used from inside the vehicle using the 12V accessory port. This accessory port is common on most modern vehicles; it's the outlet that looks like a cigarette lighter socket. While the in-vehicle method may take a little longer, it's a great option to have on a snowy or rainy day, or when you're alone in a dark parking lot or on a busy road with lots of traffic. To jump start your car using this method, here are the most common steps:

1. Turn off all accessories in your vehicle and connect the 12V jumper cable to the jump starter
2. Turn the ignition switch to the Accessory position or push the START button (depending on your vehicle)
3. Plug the 12V jumper cable into the 12V accessory port
4. Wait for the portable jump starter to indicate that it's ready (for the 1000A, it will indicate "Output Ready" and show 5 solid charging bars); this may take up to 15 minutes
5. Start your vehicle
6. Disconnect the 12V jumper cable from the accessory port and from the jump starter

If your car still won't start after trying the in-vehicle method, you may need to try the direct-to-battery method instead.

Note that you should drive your vehicle for at least 20 minutes after the jump start so that the vehicle's battery can recharge.

No matter which method you use to start your vehicle, you should fully recharge your jump starter after each use – particularly if you've used it to start multiple vehicles – and at least once every 12 months for best battery performance. Both Cobra models feature an at-a-glance status indicator so you can easily see your battery charge level.

Are Jump Starters Safe?

When used according to the manufacturer's directions, jump starters are perfectly safe and an incredibly useful tool to have on-hand in case of a dead vehicle battery. You won't need to call and wait for roadside assistance to come to you or flag down a passing vehicle to ask for help jump starting your car or truck. In certain situations, your vehicle may even be parked in such a way that makes it difficult or impossible for jumper cables to reach your battery from another vehicle, which makes having your own jump starter invaluable.

Before using any portable jump starter, make sure that it's fully charged, and that all cords and plugs are in good condition. Never use a device that has been damaged or modified, submerged in water, or exposed to rain, snow, or other forms of moisture for an extended period. Portable jump starters should not be used in the presence of flammable fumes or gasses, such as near propane tanks or in the poorly vented bilge of a boat, or near sparks or open flame (including cigarettes).

If your car will not start after using a fully charged jump starter, the battery may be completely dead or damaged, or you may have a problem with your starter, alternator, or other system. It's best to take your car to a mechanic to determine if there’s an underlying problem that goes beyond a drained battery. In any case, a portable jump starter can prove to be an incredibly helpful tool for yourself, your loved ones, or even for other stranded motorists who could use a quick jump start.