How Long to Charge a Car Battery at 40 Amps

A 40 amp battery charger is an extremely powerful device. The average car battery will provide about 48 amp hours before it is depleted of power and a 40 amp battery charger would restore that number of amp hours in an hour or less.

There are some real drawbacks to having a 40 amp car charger. The perfect car battery charger is one that will slowly provide a steady amount of amps for several hours until the battery is completed recharged. The 40 amp battery charger delivers such a powerful number of amps in an hour that they can damage the battery they are charging.

If you charge a battery really fast the plates that conduct the transfer of power from one battery cell to the next can become warped or buckled. When these plates become warped or buckled they stop making good contact with the other battery components and the battery loses power. Sometimes when these plates are warped or buckled the battery can be damaged beyond repair.

Larger Batteries

Larger batteries are better suited for a powerful charger like a 40 amp battery charger. Most larger batteries, the ones that provide 100 amp hours or more, are marine batteries that are used on boats, watercraft, or even in helicopters and airplanes.

The average homeowner rarely has a need for a battery charger that can produce forty amps of energy per hour.

Can a 40 amp charger be useful?

A 40 amp charger can be useful if your car battery is completely dead and you need to get the engine started in as short an amount of time as possible. If you have ever had to jump start your car by connecting the battery of another running car, to your car battery, then you understand how hooking a 40 amp battery charger to your dead battery would work. The power the large charger would provide would be an instant boost of power to your car.

The problem with that instant boost of power is that the boost will last only about ten to fifteen minutes, so you must immediately drive the vehicle and either go straight to a mechanic for service or hope and pray that your alternator kicks in and starts recharging your battery.

If you use a 40 amp battery charger to quick start your car you should turn off all unnecessary items. This will allow the battery to power the most important components of the engine for a longer period of time. Components that drain amps from your battery include:

  • Radios
  • Air conditioners
  • Interior lights
  • Headlamps
  • Electric seats
  • Heated seats
  • Electric powered windows
  • DVD players and accessories like this

If you do plan to buy a 40 amp charger then the ultimate car battery charger for you is one of the smart chargers or fully automated chargers. The smart chargers have sensors built in them that control the number of amps the charger provides to the battery. With smart chargers you get:

  • A charger that will not overcharge your battery
  • Minimized risk of battery damage
  • A charger that you can leave connected to your battery because it will either reduce the charge it provides so drastically that it cannot damage the battery it is connected to or it will shut off automatically when the battery has reached a full charge
  • A charger that can determine whether the alternator on your vehicle is working properly
  • A charger that can determine the health of your battery and alert you to possible damages

Learn more about the other AMP factors for a car battery charger:

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      RUF - Car Chargers & Others