Nickel Cadmium (NiCd) batteries are broadly utilized in shopper electronics on account of their excessive power density and lengthy life. Fixed present charging is commonly really helpful by producers. A number of web sites, together with Wikipedia, recommend safely charging NiCd batteries at a 0.1C charge, that means at 10% of their rated capability, for 14 to 16 hours, as an alternative of 10 hrs.
Sluggish charging doesn’t trigger a temperature rise, which can have an effect on the lifetime of the battery. Extra power should be provided to the battery than its precise capability to account for power loss throughout charging. Therefore, 14 to 16 hours of charging as an alternative of 10 hours.
Wow the engineering world together with your distinctive design: Design Concepts Submission Information
The battery charger
Determine 1 offers the circuit for gradual charging a NiCd battery pack with two AA-sized 1200-mAH cells. The battery is charged with 120 mA (10% of 1200 mA) fixed present for about 15 hours.
Determine 1 The circuit for a low-cost NiCd (2 AA dimension 1200 mAH battery pack) gradual charger with cost capability indicator. Every phase within the U5 and U6 LED bar graphs signifies a cost capability rise by 10%. Because the charging present is fixed, the time period of charging signifies the cost capability. After 10 hours, the battery ought to be totally charged. Charging for just a few extra hours than obligatory provides extra power to account for power loss throughout charging. R2 and C1 are for the ability ON reset of counters. The Vcc and floor pins of U2, U3, U7 and U8 aren’t proven right here. They should be linked to 9-V DC and Vss, respectively. Time accuracy will not be es. Every phase could glow for about 1 hour.
Each hour of charging is indicated by the glow of 1 LED bar graph phase (U5 and U6). After 15 hours, charging stops robotically. This isn’t a microcontroller-based circuit, in order that even folks with out programming information or a programmer gadget can construct this circuit. A crystal-based timing circuit will not be used right here, as there isn’t any necessity for time accuracy.
The way it works
U1 is 555, configured as an astable multivibrator to generate a pulse prepare of width 0.88 seconds. R7 could be changed by a 50K resistor and a 50K multiturn potentiometer in collection for adjustment. LED D2 blinks at this charge.
U7 divides this pulse prepare. Dividing by a 212 output at pin one yields a pulse prepare with a pulse width of 1 hour. U2A counts these pulses.
U3 is a 4- to 16-line decoder with an energetic LOW output. The chosen output goes LOW, inflicting the corresponding bar graph phase to glow, whereas all different outputs stay HIGH. Because the sixteenth output at pin 15 of U3 stays HIGH, Q1 turns ON and the battery begins charging, and D1 begins glowing.
U4 is configured as a continuing present generator. With R3 set as 10 Ω, the charging present is ready at 100 mA, which is 10% of 1200 mA.
In the course of the first hour, the output of U3 at pin 11 goes LOW, and the primary phase of the LED bar graph U5 glows. After 1 hour, counter U2A increments as soon as, and the output of U3 at its pin 9 goes LOW, which causes the second phase of the LED bar graph (U6) to glow.
This course of goes on till the fifteenth phase glows to point the 15th hour of charging. When the 16th hour begins, the 16th output at pin 15 of U3 goes LOW, turning Q1 OFF.
Now charging stops, and the “Charging ON” LED D1 goes OFF. This LOW output, linked to U8B inverter enter, outputs HIGH on the U2A clock enter, which disables additional counting. Therefore, Q1 continues to be OFF. At this level, the battery is totally charged and turns into prepared for utilization.
Jayapal Ramalingam has over three many years of expertise in designing electronics methods for energy & course of industries and is presently a contract automation guide.
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