When checking the density of the electrolyte in the battery, the readings of the densimeter are compared with its tabular values.
| Density, g/cm³ | Middle zone | South of the country |
| The battery is discharged | 1,15 | 1,10 |
| AB is half discharged | 1,22 | 1,17 |
| AB is charged | 1,26 | 1,22 |
The density of the electrolyte in all the AB cans must be the same and differ from each other by no more than ±0.02 g/cm³. If the density of the electrolyte in adjacent cans differs sharply, then there is a short circuit in the AB and it is faulty.
Battery fault diagnostics
Cause | Elimination |
| The output power is too low, the voltage drops significantly | |
| The battery is discharged | Charge the battery |
| Too little voltage from the voltage regulator | Check and, if necessary, replace the voltage regulator |
| Poor or oxidized contact | Clean the contacts, especially the lower part, and lightly lubricate with acid-resistant grease: tighten the fastening screws |
| Poor ground contact between battery-engine-body | Check the ground connection, if necessary ensure this contact: replace oxidized or brown-coated fastening screws with tinned screws |
| Excessive self-discharge of the battery due to insufficient purity of the electrolyte | Replace the battery |
| Possible sulfation (grey-white coating on the plates) | Charge the battery with a low current so that the plaque dissolves slowly. If after repeated charging and discharging the output power is still low, replace the battery |
| The battery is worn out, the active mass falls out of the plates | Replace the battery |
| Insufficient battery charge | |
| Generator or wiring faulty | Check the generator and voltage regulator, repair or replace |
| The V-belt is loose, the tensioner is faulty | Check the tensioner, replace the V-belt if necessary |
| Too high load is turned on | Install a battery with a higher capacity, it is also possible to use a more powerful generator |
| Electrolyte level too low | |
| Recharge, Evaporation (especially in summer) | Add distilled water up to the mark (with a charged battery) |
| The density of the electrolyte is too low | |
| The battery is discharged | Charge the battery |
| The density of the electrolyte in one of the cans is significantly lower than in the others | Short circuit in the bank. Replace the battery |
| The density of the electrolyte in two adjacent cans is significantly lower than in the others | The dividing wall is not hermetically sealed, which causes a conductive connection between the cans, discharging the plates. Replace the battery |
| Short circuit in the on-board circuit | Check electrical units |
When checking under load, record the voltage drop when starting the engine, the battery voltage should not fall below 8.0 V, at an electrolyte temperature of +20°C. Checking the battery with high currents should be carried out using the Bosch T.12.200.E tester at a service station and according to the instructions for the device. This test is currently the most reliable method for judging the battery charge and its physical condition (short circuits of plates and their sulfation).
Attention! The battery is subject to spontaneous discharge during vehicle storage. Battery recharging should be performed every 45–50 days.
You can recharge the battery in a car only when the engine is not running. Before recharging the battery, remove the "-" terminal from the car's on-board network.
If the car is stored for a period exceeding 1 month, it is necessary to remove the "-" terminal of the vehicle's on-board network from the battery. If the car is stored for a period exceeding 1.5 months, it is necessary to remove the battery, charge it and store it in a cool room, but at a positive temperature. It is recommended to recharge the stored battery every 3 months. Each discharge, especially a long one, reduces the service life of the battery. The electrolyte level should be between the "MIN" and "MAX" marks on the battery body. If the level is lower, remove the plug and add distilled water.
The control charge of the battery must last at least 5 hours using a charger of the type "Gossen CG 32" or "Siemens/Gossen VB 801". Full charging of the battery continues until the state of charge exceeds 80% of its capacity.