How to Charge a Car Battery at Home

Have you ever been in a situation when your car just doesn’t want to start? Then you know how frustrating it may be, especially when you are in a hurry. To make things worse, these mishaps seem to happen at the worst times, or at least it would appear so at the moment. Because of the sheer complexity of your car and the amount of parts and components, there are many problems that can cause this. However, paying attention to what happens when you turn the key can reveal a lot.

If there are faint clicking noises from under the hood and dashboard lights dim, chances are you have a flat battery. In this article, you will learn why batteries go flat, what to do when this happens, and how to prevent it.

Charging your car battery at home.

Why Do Batteries Go Flat?

Even when your car is not running, there are several systems that use some amount of electricity. Starting from simple things like a dashboard clock to more complex ones, such as an alarm or remote locking system, are always on. As this draws power from the battery, it can go flat if your car has been sitting on your driveway for more than a week. And if you leave the stereo or lights on by accident, it will take only a few hours until your battery is dead.

The battery itself, no matter how good and durable it may be, will wear out with time. When this happens, it will lose its ability to hold enough charge to start your car in the morning. Although adding distilled water or cleaning traces of corrosion may sometimes help, in most cases, you will need a new battery. However, it is best to check the car electrical system before blaming the battery. A faulty alternator, parasitic drains or corroded battery terminals can all create symptoms similar to the worn battery.

How to Use a Battery Charger?

Using a battery charger is the best way to restore the power to your flat battery. Despite this being a straightforward procedure, there are several things to consider when charging the battery. First of them is the battery charger you will use. In most cases, older ones require manual adjustment and control. To be on the safe side, set the amperage to the lowest available level, check the charger from time to time and unplug it when it reaches 100%. On the other hand, modern ‘smart’ chargers, use microprocessors that tests the battery condition, selects an optimal charge rate and shuts off on it own.

Another common question is whether to remove the battery from the car during the charging process or to leave it connected. While some say that voltage spikes that occur during charging may damage sensitive electronic devices and that the lead-acid batteries may explode, this is not likely if you follow some simple rules. Yet, charging the battery while still connected to the car is easier, especially where access to the battery may be very limited. In addition, by disconnecting the battery, you will lose various settings, such as channels in your stereo or stored seat positions.

The charging procedure is simple and safe, as long as you follow these steps:

  • Start by inspecting the battery for any signs of damage, cracks, or leaks. If there is anything like this, you must replace the battery. Besides being unreliable, damaged or leaking batteries can cause further damage to your car and pollute the environment. 
  • If you have a wet-type battery, check the electrolyte levels in all six cells. You can do this by removing plugs on the top of the battery. If any of them is not flooded all the way up, top it off with distilled water.
  • Before connecting the battery charger, identify positive and negative battery terminals by looking for markings on the battery itself. Although red positive and black negative is the usual combination, never rely just on the cable color.
  • With all checked, connect positive charger lead to the positive battery terminal, and negative charger lead to the car chassis, as this will prevent sparkling.
  • Select an appropriate setting on the charger, depending on the battery type you have. Even with the automated charger, you still have to select between wet and AMG batteries. With all set, turn on the charger and make sure that everything is in order. Have in mind that with manual chargers you have to monitor the charge level. 
  • With the battery charging process finishes, first turn off the charger. When removing battery charger leads, start by disconnect negative charger lead, followed by a positive one.

When Should You Use a Battery Tender?

If you are not using your car for several days, connecting it to a battery tender will help keep the charge at desired levels. These devices, sometimes called trickle chargers, are much smaller and cheaper version of a traditional charger. While not suitable for charging flat batteries, you can use them recharge the battery at the same rate as the self-discharge. Most battery tenders will shut or go into a “float” mode when the battery reaches full charge. This, combined with small outer dimensions, make it an excellent preventive option when you don’t drive your car often.

Is It Safe to Use Jumper Cables or a Battery Booster?

While chargers or tenders will give best results and ensure maximum longevity of your battery, using them requires preparations and certain amounts of time. In most cases, it is the time you don’t have, as you need the car up and running with no delay. In such situations, having a battery booster can be a lifesaver. Providing a strong stream of electricity, this special device will provide a boost of power that will help start your car. Because boosters are nothing more than a more powerful version of a battery tender, using them is very similar. The only real difference is that after attaching booster cables to the battery, you can try starting the car just after connecting the booster.

Other option jumpstarting, which is a quick way to your car by borrowing electricity from a working one. Although simple, the jump-starting procedure requires caution in order to avoid damage to the working car.

  • Start by parking the assisting car nose-to-nose with yours as close as possible. Make sure that both vehicles are in ‘park’ with emergency brakes engaged and that engines are off.
  • Lift the hoods on both cars and locate positive and negative battery terminals. Clamp the red end of the jumper cable to the dead batteries positive terminal and the other end of the red cable to the functioning cars positive terminal. Attach the end of the black cable to the working battery’s negative terminal and the other end to a metal section such as a bracket or bolt a foot or more away from the battery to ground in the dead car.
  • Start the working car and let it run one to two minutes while keeping the engine between 2000-3000 RPM. This will ensure that the alternator produces enough current to charge your car.
  • Try to start your car. Although it may take several attempts, avoid trying to start the car for three or four times in a row, as this could damage the electrical system.
  • Once the dead car is running, disconnect the cables in the reverse order you connected them. Make sure that clamps don’t come into contact while you are removing them.
  • It will take some time until the alternator in your car recharges the battery, so you will need to drive the car for at least 10 minutes.

Whether you are using a battery booster or jumper cables, your car may still refuse to start even after several attempts. This may be a sign of a deeper problem, such as a dying starter, faulty ignition or bad fuses. Sometimes, it may be something simple as a corrosion build-up on battery terminals.

How to Make Your Battery Last Longer

While there are several options for recharging dead batteries, the best solution is to make sure it doesn’t drain in the first place. Because preventing is far easier than curing, following these simple steps will help your battery last longer and make your car more reliable.

  • Make sure the electrical system of your car is in good condition. Start by checking the battery terminals, which must be snug and with no traces of corrosion. Also, all wires and connectors should be firm and with no visual damage.
  • With the engine on, the alternator in your car should produce 14 V to 15 V at any given time. Values outside this range are a sign of an alternator failure. You can check the output of you alternator by using a multimeter to measure voltage on the battery terminals when the engine is running.
  • Always use a batter sufficient for your car. Besides the overall size and position of terminals, it is important that the battery has enough amperage and cranking power. This will make sure your car starts even in extreme temperatures, as they have a negative impact on battery life and capacity.
  • Deep-discharging that happens when you leave a low-current consumer, such as interior lights on for a long time, can irreversibly damage the battery. If the battery has suffered from deep-discharging, have it recharged as soon as possible. Never keep a battery drained for long periods of time.



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