Automatic charger for nickel-cadmium batteries. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells
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A fairly simple automatic charger for nickel-cadmium batteries can be made on the basis of a timer, as shown in Fig. 5.34.
Rice. 5.34. Diagram of an automatic charger
The circuit can operate both separately and as part of radio equipment to maintain a fully charged backup battery. In this case, such a battery always remains connected, regardless of whether it is currently used to power an external device or not.
In this case, the timer chip operates as a two-threshold comparator with a powerful output stage. The reference low voltage for two comparators is supplied from the zener diode VD1 to the input DA1.5. The timer output can be 0 or 10 V - depends on the voltage at other threshold inputs. Their level is set by trimmer resistors so that there is a hysteresis between the appearance of voltage on DA1.3 and its shutdown.
To set up the circuit, instead of a battery of batteries, we turn on an adjustable constant voltage source.
For ease of adjustment, trimmer resistors are best used multi-turn.
By changing the source voltage, the trimmer resistor 7 ("Off") sets the required final battery charge voltage (usually 1,4 V per battery cell), and R5 ("On") - the voltage at which charging is turned on (usually 1,1 V per battery). element).
The maximum battery charge current depends on the value of the resistor R3 and is chosen so that it is not more than 0,1 tons of battery capacity, indicated in ampere-hours (Ah), but not more than 200 mA (this resistor is also the output current limiter of the microcircuit). Diode VD2 prevents the battery GB1 from discharging through the output of the microcircuit when there is a zero level on DA1.3.
Capacitors C2 and C3 prevent the influence of interference and the operation of the microcircuit, and the glow of the HL1 LED indicates that there is no recharging at the moment.
Author: Shelestov I.P.
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