مجتمع صنعتی سپاهان باطری

There are four different methods for charging batteries:

Normal charging

Normal charging recharges a fully or partially charged battery to 100%. Normally a charging current is selected which amounts to between 1/20 and 1/10 of the battery capacity. It is important that the charging current is lowered when the voltage which causes gas to develop is reached (gassing voltage). The current is switched off when the battery is charged.

Back to top of page

Fast charging

This charging method charges the battery with a current which is between 3 and 5 times greater than the normal charging current, so that the battery reaches an acceptable charge state quickly. When the gassing voltage (2.35 to 2.4 V) is reached, the charging current should be reduced to avoid overcharging. You should only perform a fast charge on a battery in isolated cases.

Back to top of page

Buffer charging

The battery, charger, and power consumers are all connected to each other. The charger delivers a current which is just enough to keep the battery's charge state at 100%. The battery delivers peak loads to the "consumers". In buffer charging, it is charged with a constant (stable) voltage.

Back to top of page

Charging with a low current

If the battery is charged but not in use, it can self-discharge after a short while. This amounts to 0.1 to 1% per day. Charging with a low current compensates for this discharging. The charging current in this case is 0.1 A per 100 Ah.

Back to top of page


Choosing a charger is extremely important for the reliability and life expectancy of the battery. Apart from performance, there are also differences in the charging characteristics and other specific properties.

  • Unregulated chargers
    The most-used chargers are unregulated chargers (W characteristic) and are not well suited for maintenance-free batteries.
  • Regulated chargers
    With regulated chargers (e.g. UI characteristic), the real-time actual values for the charging current and charging voltage are transmitted to a regulator which performs a target/actual comparison to eliminate any deviations. This means the charger can be connected to the battery for a longer time without any risk of danger.

Back to top of page

Charging characteristic

The characteristic indicates the relationship between charging current and charging time. The charging characteristic is the function of the current (A) in which the charging voltage (U) is presented as a curve.

The W charging characteristic
For lead-acid batteries.
Fast charging is possible with the correct charging current.
  • Constant voltage (<14.4 V), fluctuations in the mains voltage can be avoided by using an inductor or inverter transformer
  • Charging current drops as voltage rises
  • Current depends on internal resistance of the battery
  • Supervising the battery charging is recommended so as to avoid overcharging.
The IU charging characteristic
For lead-acid batteries but also for gel batteries.
  • Constant voltage (<14.4 V), fluctuations in the mains voltage can be avoided by using an inductor or inverter transformer.
  • Current remains constant at 2.4 V per cell until gassing voltage is reached when it drops to zero
  • Constant voltage - falling current
  • The battery can be charged without supervision. If the battery is fully charged the charging current will be so low that overcharging is not possible.
  • This method is suitable for extremely fast and partial charging of batteries. Charging the battery to 100% takes longer.
The IU0U characteristic
  • Gel batteries can only be completely charged with IU or IU0U chargers
  • After charging at a constant voltage, the voltage is held for some time and then driven down again once the gassing voltage of 2.4 V per cell has been reached.
  • The current reduces to the conservation charge level.

Back to top of page

Return to Battery service