Note that the stability is observed when the load current and will change slightly of the supply voltage. Likewise, the fact is usually overlooked, but if you want a perfect stability – stabilize the power supply. Calculation of the current is very simple – the current in amperes is equal to 1.2 divided by the resistance R1 in Ohms. To display the current used transistor (germanium necessarily because of the low voltage opening) that allows you to visually observe the currents to 50 mA.
Diode D1 and F2 fuse protects the charger from the battery reverse. Capacitance C1 is selected from the formula: 1 amp should 2000uF.
The advantages of the proposed device: short-circuit protected it does not matter the number of elements in rechargeable battery and type – can be charged and sealed acid and lithium 12.6 3.6 and 7.2 V alkaline Switch current should be included exactly as shown on the chart – in order to remain in any manipulation of the resistor R1. The use of alternating low-impedance resistor is undesirable because of instability of sliding contact with load currents over 0.2 A.
Limitations: The maximum voltage rechargeable battery must be less than the supply voltage of 4 volts; 142EN12 chip installed on a heat sink, dissipating 20 W in the case of a single charge of the alkali element maximum current of 1A.
Charging current capacity of 0.1 is suitable for all types of batteries. To fully charge the battery, he must give 120% of the nominal charge, but before that he should be fully discharged. Consequently, the charging time in the recommended mode – 12 hours.
Suggestions to stop charging to achieve a certain voltage should be treated with some caution – as a rule, the battery voltage after removing the charge current gradually decreases, and this leads to re-activate the charge, if the comparator is set low hysteresis, in addition, the criteria for selecting the voltage – different for different batteries.