How to jump-start a car battery

September 27, 2022 by PEMCO Insurance

Jump starting a carDon’t let a dead car battery leave you stranded, especially as fall’s cooler weather puts an added strain on older or already weak batteries.  

Here’s how to connect jumper cables to safely jump-start a dead car. Plus, why you should consider using roadside assistance instead (available as a low-cost add-on to your PEMCO policy*). Also, we'll share our top strategies to prevent a dead battery in the first place.

12 steps to jump-start your car 

If you’re comfortable trying to jump-start your car and it’s safe to do so, make sure a dead battery is really the problem. It’s likely, for example, if you can see that you accidentally left the lights or accessories on without the engine running. Signs of a dead battery include the engine failing to crank (or cranking weakly) and the accessories not working. You may hear a clicking sound and nothing else as you turn the key. 

You can breathe life into most dead batteries (at least long enough to get home or to a repair shop) as long as you have a set of jumper cables and another driver willing to lend their car as the jump vehicle.  

Here’s what to do: 

  1. Check your owner’s manual to make sure jump-starting is safe for your vehicle. For example, you can jump-start a dead hybrid or use it to start a conventional engine, but how to do it varies from model to model, so it’s important to check even if you’ve jump-started other vehicles in the past. 

  1. Park the disabled car and a booster car hood-to-hood or side-by-side, but not touching. Turn off the ignition and accessories in both cars, put them in “Park” or neutral and set the emergency brakes.  

  1. Shield your eyes with safety glasses, wear gloves, and to avoid a shock hazard, remove jewelry including rings and watches.  

  1. Start at “RED DEAD.” Clip one end of the red jumper cable to the red positive (+) post of the dead battery. If the posts are corroded, clean them first with a wire brush or post cleaner. Don’t touch the metal ends of the cables and, once you’ve started hooking them up, never let the clamps touch each other. It helps if there’s another person available to hold and keep them separate as you focus on attaching them. 

  1. Connect “RED LIVE.” Clip the other end of the red jumper cable to the red positive (+) post of the booster battery. Take care not to let cables dangle in either engine compartment, potentially becoming entangled in belts or other moving parts. 

  1. Connect “BLACK LIVE.” Clip one end of the black cable to the black negative (-) post of the booster battery. 

  1. Finally, connect “BLACK DEAD ENGINE BLOCK.” Clip the other end of the black cable to an unpainted, relatively clean part of the engine block or frame of the disabled car. DON’T CLIP IT TO THE BATTERY! It may create a spark, so choose a bolt or bracket away from the battery, fuel or wiring. Also, avoid the exhaust manifold or other parts that get hot. 

  1. Start the booster car and let it idle for a few minutes to feed current to the dead battery. 

  1. Turn the ignition key of the disabled car. If it doesn’t start within seconds, stop cranking and jiggle each cable end. You might have a bad connection. Then try again. If the disabled car still doesn’t start, it’s time for a tow. 

  1. Let the cars idle together for a few minutes. 

  1. Remove each cable end in the reverse order that you attached them. Take care not to let the metal ends of the cable touch each other, just as you did when hooking them up. 

  1. Drive your jumped car for at least 20 minutes to help the battery charge. Then connect it to a battery charger to fully revive it and consider a visit to your mechanic to get the battery checked out. 

How to jump-start your car without another vehicle 

If you often drive through remote country (where other drivers are few) or you’re simply uncomfortable asking a stranger for a jump, consider carrying a portable jump box. Not only can it give your dead battery enough of a charge to start, but it also may be able to recharge a dead cell phone. Models and prices vary (many for around $200 and some significantly less), but they’re typically all-in-one units with the jumper clamps built in as well as a USB port for charging other electronics. Consumer electronics reviewers at CNET recently named their top picks for portable battery chargers.  

Roadside assistance for jump-starting  

While your first thought for dealing with a dead battery may be to jump-start it yourself, it may not be the best choice. Jump-starting a car can be dangerous for you, your car and people standing nearby if you don’t know what you’re doing. Flying sparks and battery acid (from exploding batteries, typically during jump-starting) are significant causes of eye injuries in the United States, right up there with household chemicals and workshop or yard debris. 

If you’re unsure how to jump-start a car, your best bet is to call for help and leave it to a professional mechanic. If they can’t get it started, they can arrange to have your car towed to a repair shop. 

You can add basic roadside assistance to your PEMCO policy* or, if you want extra perks like a travel agency, consider signing up with a company like AAA. If you have cellphone service, an expert is always a call away. 

Even if you know how to jump-start a car, there are certain times when you shouldn’t. Those include being in an unsafe situation where you could be struck by a passing car as you work on your vehicle, your battery is cracked or leaking, or your battery terminals are heavily corroded (buildup of crystalized or powdery white or green material) and you have nothing you can use to clean them off. Never try to brush off corrosion with bare hands, and cover your mouth and nose to avoid inhaling any of the dust. 

RELATED: The hazard of disabled vehicles on the shoulder | PEMCO 

How to prevent a dead car battery in the first place  

If they haven’t already, most Washington and Oregon communities soon will experience their first freezing temperatures of the season, meaning cars with weak batteries will have more trouble starting in the morning.  

Car batteries can be surprisingly short-lived. Many of our Claims experts simply replace their batteries every three years to reduce the chance of being stranded, since that’s the age when batteries commonly start to fail. If yours has managed to reach the five-year mark without needing a jump-start, consider yourself both lucky and likely due for a visit to your mechanic or auto parts store. 

Short of a battery replacement, these tips can help you start your car on cold mornings: 

  1. Park in a garage if you can. While temperatures may still dip below freezing inside your garage, it’s probably at least a few degrees warmer than outside. That may be just enough to preserve precious battery power, which drops in cold temperatures.  

RELATED: 6 tips to organize your garage | PEMCO 

  1. Get your battery tested. If your car is slow to start, ask your mechanic to check your battery’s strength to determine if it’s time to replace it. Your mechanic also can diagnose whether something else, like your alternator, is at the root of what seems to be a battery problem. 
    Perhaps surprisingly, electric vehicles often have an easier time starting in cold weather than gasoline-powered cars. That’s because their batteries just need to start a few electronics rather than turning over a cold engine. 

RELATED: Is now the time for an EV or hybrid? | PEMCO 

  1. Turn off all accessories before trying to start. That includes the lights, radio, seat and steering wheel warmers and front and rear defrosters, all of which draw energy from the battery.  

  1. Turn the key for no more than 20 seconds. If the engine doesn’t start, wait a minute or two and try again. Over-cranking can damage the starter.  

  1. Don’t flood the engine. See your owner’s manual for starting procedures. Generally, don’t touch the gas pedal when starting fuel-injected cars, and follow preventative maintenance schedules to keep fuel injectors clean. For older carbureted vehicles, briefly depress and release the pedal when starting if recommended. Stuck, dirty fuel injectors or holding the pedal down too long increase the risk you’ll soak (“flood”) the spark plugs with fuel. If that happens, open the hood to help the excess fuel evaporate and try to start again in about 20 minutes.  

*PEMCO’s Towing & Emergency Road Service is a low-cost, add-on coverage that gives you benefits like jump-starting, flat tire changes, gas (if you run out) and emergency towing for about $10 per year, per vehicle, if you opt for $100 in towing reimbursement. You can add it as long as you have Bodily Injury and Comprehensive coverages on your cars. Call 800-GO-PEMCO or ask your local PEMCO agent for details.  




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