Checking the electrolyte level
The electrolyte level in individual jars must be between the MIN·marks (1) and MAX (2). If necessary, unscrew the AB plugs (3) and add distilled water.
Voltage test
The state of the battery is checked by measuring its voltage. Disconnect wire from AB.
Before checking, the battery must be discharged for at least 2 hours. Connect the battery to the voltmeter and measure the voltage.
Measurement results:
- 12.7 V or higher - battery in good condition;
- 12.5 V - normal state;
- 12.3 V or below - Battery in poor condition, charge or replace it. Connect wires to AB.
Battery check under load
Connect a voltmeter to the AB contacts.
Start battery and measure voltage.
In the process of starting the engine, the voltage on the battery should not fall below 10 V.
If the voltage drops sharply, and in different AB banks the electrolyte has a different density, then this indicates a faulty AB.
Electrolyte Density Check (not carried out on unattended batteries)
The density of the electrolyte, together with the results of voltage measurements, makes it possible to draw an accurate conclusion about the state of charge of the battery. A hydrometer is used for measurements. Electrolyte density is measured in g/ml (g/cm3) or degrees.
When measuring, the following values can be obtained (electrolyte temperature 20°С).
Check all the AB banks in turn - they should have the same electrolyte density (allowable difference - 0.04 g / ml). If this is not the case, then the AB is defective.
Battery self-discharge
Depending on the vehicle configuration, the natural self-discharge of the battery is supplemented by current consumption by various control units and systems in the non-working state. At the same time, on a non-working car, you need to recharge the battery every 6 weeks. If there is a suspicion of leakage currents, then you need to check the electrical equipment as follows.
A charged battery is used for testing.
Turn off all current consumers, including clocks and other non-switchable consumers.
Close doors, hood and trunk
Disconnect the negative cable from the battery.
On the ammeter (with measurement limits 0-5mA and 0-5A) turn on the maximum measurement limit. Connect an ammeter between the negative terminal of the battery and the negative wire connected to it.
Attention: The test can also be carried out using a test lamp. If the lamp connected between the negative wire and the negative terminal of the battery does not light, then an ammeter must be used.
Turn on the measurement limits on the ammeter in turn until a readable current value is obtained (maybe 1-3 mA).
Pulling the fuses in turn, break the various circuits. If, when a fuse is pulled out, the current drops to zero, then you need to look for the cause in the corresponding circuit. The reasons may be as follows: corroded or dirty contacts, frayed wire insulation, internal circuit in the units.
If no faults are found in the fuse-protected circuits, then it is necessary to disconnect the wires from the components that are not protected by fuses: the ignition system, generator and starter.
If the current drops to zero when one of the unprotected units is disconnected, then the parts must be repaired or replaced. In case of current leakage in the starter or in the ignition system, the ignition switch must also be checked.
Connect the negative wire to the battery, restore the clock and radio tuning.