How Long To Charge A Car Battery At 40 Amps

40 amps is a large charging voltage and can charge your car battery incredibly quickly.

In a matter of minutes, you can start your car again. You must take care not to leave the battery plugged into the charger for too long, as this can overcharge it.

Overcharging can damage your battery and reduce its lifespan. 

Standard car batteries have 48 amp hours of power. This can be replenished by a 40 amp charger in under an hour. This can cause issues as the charger is so powerful it can cause damage to the battery.

This is because the power conducting plates on the battery can buckle or become misshapen if there is too much power running through too fast. 

What Should You Use 40 amp Chargers For?

Larger batteries (100 amp hours and more) will hold up better to a 40 amp charger being used. These kinds of batteries tend to be found on boats, large watercraft, airplanes, and helicopters. 

If your car battery is completely dead and you need to start the car soon, a 40 amp charger is very useful. This will have a similar effect to jump starting your car from another running car engine. The large boost of power will force the engine to kick back into action speedily.

If you use this method to restart your car, you will likely only get around 10-15 minutes of power from it. This is unless your alternator begins to work and starts to recharge your car battery. For this to happen, you will need to drive your car immediately to push the alternator to run. 

For this reason, we recommend keeping a 40 amp charger in your car for emergency situations. This means that if your battery runs out, you do not need to wait for a friendly stranger to give you a jump start!

How To Use A 40 amp Battery Charger

Before attempting to start your car, you should ensure all unnecessary power outages are switched off. This will enable the power to be routed directly to the engine rather than to additional electrical features.

We recommend turning off the car heaters, air conditioning, radios, lights (internal and external), electric and heated seats, DVD/CD players, and electric windows.

What Are The Benefits Of Smart Chargers?

These are also known as fully automated chargers. They have built-in sensors that adjust the number of amps delivered to the battery based on the battery’s charge level. These ensure that your battery does not overcharge and get damaged. 

This means that you can walk away from the charger and leave it plugged into the battery. The smart charger reduces the amps sent to the battery when it nears full charge and even has the capacity to switch off when the battery is ready for use. 

They can also give you additional information about the state of your car. These include letting you know whether the alternator is functioning correctly. Smart chargers should also be able to tell you the rough health of your car’s battery and indicate areas of potential damage. 

As with any heavy-duty electronic appliance, it is wise to seek professional advice if you are unsure of how to perform any of these steps. Your car’s owners manual is also a good place to look for advice tailored specifically to your vehicle.

What Are Trickle Chargers?

These are chargers that direct small amounts of power to your car battery over a long period of time. They can be known to take more than 2 days to fully charge a battery. 

Trickle chargers generally only supply 1-2 amps of power which is why the process is so slow. This is beneficial as it ensures your battery will not become overcharged or overheat. 

This is a good option for people who don’t drive their cars frequently but wish to keep the battery charge topped up.

How To Charge A Car Battery

Take care when removing and charging your car battery to wear gloves to protect your hands from any battery acid. If your car and battery are in good condition and looked after correctly, they should not need recharging more often than 5 years. 

Ensure your car is turned off before you begin the charging process.

Pop the hood of your car and locate the battery underneath. Check the terminals for signs of damage and then carefully clean them. If you notice any white powder do not touch this. It is likely dried sulfuric acid which is highly corrosive to skin. 

Clean the terminals with sandpaper, followed by a damp cloth and baking soda. Wipe the terminals dry. 

Look to see if your battery has cell caps. These are located either on the top of the battery or under a yellow strip. They must be removed before you start charging to allow space for the gases to escape. Not all batteries have these, so do not worry if you can’t find them. 

Attach the red wire to the red (positive) terminal on the battery. This should be connected first. After this, connect the black wire to the black (negative) terminal. Do not allow the ends of the wires to touch as this can create sparks. If any hydrogen gas has escaped from the battery, these sparks could cause the gas to combust and this could lead to serious injury. 

When you have successfully connected both of the terminals to the wires, connect the charger to your mains socket. Turn on the power supply and leave the charger to work. 

Turn the charger off periodically and check the reading to ensure the battery does not overcharge. Once sufficiently charged, turn off the power supply.

Carefully remove the charger from the battery.

Use a hydrometer to ascertain the energy levels in the fluid. Alternatively, turn on the car and see if it starts. If this has not solved your issue, it is likely that you will need a replacement battery. 

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