Performance characteristics of the batteries can be significantly improved if they are charged to produce an asymmetric shock. Device charging scheme, which implements this principle is shown in the figure.

Fig. 1. Charge asymmetric shocks. Scheme device

With the positive half-cycle of the input voltage current flows through the elements of VD1, R1 and stabilized diode VD2. Part of the stabilized voltage is fed through resistor R3 to the base of transistor VT2. Transistors VT2 and VT4 operate as current source, whose value depends on the resistance of the resistor R4 and the voltage on the basis of VT2. Charging current in the circuit the battery flows through the elements of VD3, SA1.1, RA1, SA1.2, then through the battery and the drop in the collector of transistor VT4, R4.
With a negative half-cycle AC operation of the device is similar, but it works the upper arm - VD1 stabilizes the negative voltage, which regulates the current flowing through the battery in the reverse voltage (current discharge).
Shown in the diagram milliammeter RA1 is used for initial setup, in future it can be disabled by moving the switch to another position.
Charger has the following advantages:
1. Charge and discharge currents can be adjusted independently from each other. Consequently, in this device may use batteries with different energy value.
2. If any outage alternating voltage each of his shoulders and rose through the battery current does not leak, that protects the battery from the spontaneous discharge.
This device from domestic items, you can use VD1 and VD2 - KC133A, VT1 and VT2 - KT315B or KT503B. The remaining elements are chosen according to the charging current. If it does not exceed 100 mA, then as transistors VT3 and VT4 can apply KG815 or KT807 with any letter indices, as well as diodes VD3 and VD4 - D226, KD105, too, with any letter indices.
Transistors KG815, KT807 should be placed on a heat sink surface area teplorasseivayushey 5 ... 15 sq. cm)