How long to leave battery charger on car

1

How to Use a Battery Charger

You should keep a portable car battery charger at home or in the trunk of your car. These standalone units connect to your car’s positive and negative battery terminals. 

How to connect a battery charger:

• Verify that your car battery charger is in the off position before starting.
• Connect the positive lead from the car battery charger to the positive terminal on your battery. This will likely be red with a plus sign.
• Connect the negative lead from the car battery charger to the negative terminal on your battery. This will likely be black with a minus sign.

How to charge your battery:

• Set your battery charger based on your needs. 
• Models vary, but most offer a “jumpstart” or “quick charge” mode for a speedy car battery charge, as well as a lower power, long-term charge mode designed to safeguard batteries and keep them in top shape.
• Turn the battery charger on and let it charge as indicated in the product instructions. 
• Quick charging can take as little as 15 minutes. Longer charges may take several hours on low mode.
• Check the battery charge indicator light if your model of charger has one. This is particularly important when trying to get a drained battery to start.

After your battery is charged, turn off the power on the battery charger. Disconnect the leads to the battery and start the engine.

2

How to Use Jumper Cables

Jumper cables can supply power via a functional battery from another car. Keep a set in your vehicle. Connecting your car's battery to another car's battery with jumper cables is a common way to recharge a battery. 

• Park the vehicles so their batteries are as close as possible. Leave enough room between the vehicles to attach the jumper cables. 
• Put both cars in park or neutral and shut off the ignitions. 
• Attach one red clip of your jumper cables to the positive terminal of the car with the working battery. Attach the other red clip to the positive terminal on the battery that needs a charge.
• Attach one black clip of your jumper cables to the negative terminal of the car with the working battery. 
• Attach the other black clip to an unpainted metal surface away from your car’s battery. Start the vehicle with the working battery. 
• Let it run for about 10 minutes. Attempt to start the car with the dead battery. 
• Check the connections and try again for at least five minutes if it does not work.

Once your car starts, remove the jumper cables starting with the negative or black leads. Follow by disconnecting the positive or red leads. Drive your car for a minimum of 15 minutes before shutting off the engine after a charge. 

Tip: See our guide on how to jump start a car for more detailed instructions on how to use jumper cables.

3

Car Battery Recharging Tips

When to use a battery charger:

• If you left the lights on in your car overnight, charge your battery and it should continue to perform as expected. 
• If your headlights or radio have been on for a long period of time without turning on the car, you should charge the battery. 
• If your vehicle has been sitting for a long period of time, the battery may be dead and can be fully fixed with a simple charge.

When not to use a battery charger:

• If your car suddenly won’t start, it may mean that you have an old battery or a more serious vehicle problem. 
• If you have a problem with your car’s alternator or charging system, these issues need to be addressed before charging the battery.

When to use jumper cables:

• If you are away from home and don’t have a portable power source,  jumper cables may be able to give you a quick start so you can get off the road and make repairs. 

When not to use jumper cables:

• If you have a car with an electronic starting system, do not use jumper cables. 
• Check your vehicle’s owner’s manual before using jumper cables if you’re unsure.