Too low capacity. Voltage drops sharply
The battery is discharged
Recharge the battery.
Charging voltage too low
Check the voltage regulator, replace if necessary.
The connecting terminals are loose or oxidized
Clean the terminals and tighten the clamp bolts. Lubricate the terminals with a thin layer of electrolyte-resistant grease or petroleum jelly.
Bad ground connection (-) battery-engine-body
Check connections, install new wire if necessary, tighten bolted connections. Replace rusty bolts with tin-plated bolts.
Too much self-discharge of the battery
Replace the battery.
Battery sulfation
Charge the battery with a small current so that the plaque gradually disappears. If the power remains low after charging, replace the battery.
The battery has served its time. The active mass of the plates has precipitated
Replace the battery.
Insufficient battery charge while driving
The generator, voltage regulator or connecting wires are faulty
Check the generator and voltage regulator. Repair or replace if necessary.
Material borrowed from an online resource (MERCEDESMAN.ru)
The V-belt is loose. The tensioner is faulty
Check the tensioner. Replace the V-belt or ribbed belt if necessary.
Too many current consumers are connected to the on-board network
Install a battery with a higher capacity or install a more powerful generator.
The density of the electrolyte in one cell is significantly lower than in the others*
Compartment short circuit
Replace the battery.
The density of the electrolyte in the two adjacent compartments is significantly lower than in the others
The interelement partition is not hermetically sealed, which leads to conductivity between the elements and their discharge.
Replace the battery.
* these positions apply only to conventional batteries