How to charge a positive earth battery

How to charge a maintenance-free car battery

Car manufacturers try to intervene on the part of the car owner in the design of the vehicle and its individual components and assemblies. Thanks to this philosophy, modern automotive repairs often relate to just replacing one unit or module with another.

The electrical system is no exception. After all, most batteries in cars are maintenance-free. Even so, it is possible to independently charge a maintenance-free car battery at home.


  • 1 design features of car batteries
  • 2 preparatory activities
  • 3 Car battery charging
  • 4 Do you need to charge a new battery?
  • 5 safety rules for self-charging batteries

Design features of car batteries

In addition to the fact that rechargeable batteries can be divided into maintenance-free and serviced, they can be classified according to the type of electrolyte. This component of every modern car battery comes in three forms:

  • with liquid electrolyte in tanks based on acid and distilled water (classic version);
  • with gel base (quite expensive, but more durable and resistant to differences in charge / discharge);
  • Electrolyte is absorbed into the non-woven polypropylene fabric (less common but more progressive type of battery).

Battery sizes

All maintenance-free car batteries have no access to their internal device. This condition leads to restrictions in the handling of the battery, so that any manipulation can only be carried out with electrical parameters.

Preparatory activities

In order to properly charge a maintenance-free car battery, it is necessary to determine the conditions under which this occurs. There are two possibilities:

  1. The battery is removed from the vehicle and moved to a power source;
  2. To carry out the process, the charging cables are connected to the battery terminals without disconnecting the consumers in the vehicle.

In both cases there are negative and positive sides:

  1. The first option has a "plus" in that you can take the battery out of the garage and control the charging process under normal temperature conditions. Most likely, however, is a reset of all electronic settings in the vehicle that need to be reinstalled.
  2. The second option comes in handy as you don't have to take a heavy battery out of the garage and back with you as there is no reset when disconnected. If the voltage drops or the charger is not configured properly, the power consumers in a car can fail, resulting in costly repair or replacement.


While this type of battery is called "maintenance free" it does not mean that it absolutely does not require any use or maintenance. Finally, the charging process takes place at the point in time at which the engine is started. And the question of maintenance concerns the manipulation of the internal chemical processes of the electrolyte.

See also: Car battery does not charge from charger - what to do?

Car battery charging

There are several battery charging options:

  • Pulse;
  • stepped;
  • reversible;
  • combined.

Everyone will lead full battery charge. The difference between them lies in the voltage or amperage. In some cases a constant voltage is maintained and in some cases a stable current.

Charge the battery without removing the car

To control the level of the current charge on the vehicle, universal voltmeters or multimeters are used. There are special automotive instruments for measuring voltage. They are inserted into the cigarette lighter. On its real-time digital display, data from the battery terminals is monitored with an accuracy of 0.01 V.

A car's 12 volt battery is charged at a voltage of 16-16.5 V. It is advisable to start charging with a clean battery, it is better to peel off the contacts of the oxide film for better contact with to get the crocodile loader. Also, when connecting the charger to the battery, there should be no cracks or obvious traces of stains.

The time required for a full charge can be calculated based on the stated battery capacity and the current output by the charger. For example, to get a battery in order, a battery with a capacity of 55 Ah, which is output by a 5.5 A charger, takes 10 hours. You need to check the state of charge with a voltmeter. A fully charged battery should read 12.6V.

If it is possible to adjust the charging current, it is preferable to choose a lower value.

This extends the service life of an automotive electrical unit. Most chargers limit the current to 15 A. With the constant voltage method, the maximum possible current is delivered during the start of charging, which is reduced to 10% of the battery capacity during the process.

Charging the garage battery

Every hour with this type of charging is controlled by the battery voltage at the terminals. When its level has reached stability and does not change for 1-2 hours, and a light "boil" begins in the banks, the process can be completed.

See also: Computer Diagnosis of Car Errors - Do It Yourself

In the combined charging method, a stable current is first supplied, and then the charge is kept at a stable voltage. The output is controlled automatically with special chargers. At the end of the process there is an independent disconnection from the power supply.

Do you need to charge a new battery?

A new battery bought at an auto repair shop is often installed in a car at no extra charge. This is possible if less than 6 months have passed since the time of production. Otherwise, partial discharge could occur.

You can charge a newly purchased battery yourself at any time. However, it is not necessary to subject them to an intensive process with a large current intensity. During charging, you must follow the safety rules for working with batteries, as harmful gases are released.

Safety rules for self-charging batteries

At home or in a garage, the car battery should be charged in a room with good ventilation. This is due to the release of hydrogen and oxygen gas mixtures. Smoking, sparks, or the use of open flames near the loading area are not permitted.

While cleaning the battery from pollution, it is impossible to use rags made of artificial materials to avoid static electricity. When the electrolyte boils, it is necessary to stop charging.