You will need
  • - voltmeter,
  • - hydrometer.
In order to measure the voltage at the battery, use a digital voltmeter, capable of making measurements accurate to tenths and hundredths of a volt.

Before the measurements, disconnect the battery from all consumers and charging devices, and wait at least two hours.

After all of the chemical processes in the banks suspended, proceed with the measurements.
Connect wire (usually black) of the device labeled "-" to the negative battery terminal, and red, marked " + " sign to positive. The contact must be tight, on the ends of the wire should be clips.
Take readings. The charge level of your battery determine the table given below.
You can measure the voltage on each battery Bank, and thus to detect the faulty.
The batteries with liquid electrolyte can determine the charge level and residual voltage according to the density of the electrolyte.

To do this, take the hydrometer. Open your tube of cans battery and take the device in electrolyte. Mark and record the readings of the density in each jar.
The following table shows the values of the density of the electrolyte corresponding to the residual voltage, for 12 and 24 volt batteries. Correlate the measured density of the electrolyte existing at the time of the measurement voltage. Output the average voltage.

Determine the charge level of your battery in percent.