Active Inverter Technology
The first stage with Active Inverter Technology involves converting the AC mains voltage to a DC voltage. High-frequency switching transistors take this DC voltage and generate a pulsed voltage with frequencies of up to 100 kHz. One advantage to this high frequency is that the transformer that transforms the voltage can be far lighter, more compact and more efficient. After the transformer, the voltage passes via the secondary rectifier and secondary filter to the battery. The secondary filter smooths the voltage to a near-perfect DC voltage (with a negligible residual ripple).
A microprocessor actively checks and corrects the target values and actual values of all the related charging parameters (especially in respect of mains voltage). A control circuit (optical coupler) is used to finally transmit any correction values to the controller for the high-frequency switching transistor.
This approach ensures that the charging process is highly efficient.
The IUoU characteristic for starter batteries shows the charging phases for Active Inverter Technology.
Until a certain voltage is reached in the battery, the charging current remains at a constant level to ensure that charging takes place as quickly as possible. At the end of this phase the battery is already 80% charged. If the gassing voltage of approx. 2.4 V per cell is reached, then the charging current will be reduced. In this charging phase the battery is fully charged (100%). The charger then switches to conservation charging. The advantage of conservation charging is that when the battery remains unused for a lengthy period there is no risk that it may automatically lose charge, since it is kept fully-charged.
The so-called IUIoU characteristic is a special charge characteristic for traction batteries.
This characteristic differs from the IUoU characteristic in that it features controlled overcharging for a specified length of time. As a result, a battery is charged to its maximum capacity. During the dU/dt charging phase the degree of gassing increases, which in turn results in the electrolyte being mixed intensively. The aim of this charging process is to achieve an even concentration of acid throughout the cell, which in turn will enable maximum energy to be obtained from the battery.