10 Level Battery Charge Indicator Circuit

The project “10 Level Battery Charge Indicator Circuit” is designed using comparator IC LM3914, used to indicates charge of battery in 10 different level. The project uses 10 LEDs to indicate the charge of battery in 10 level i.e. each glowing LED indicates 10% of charge in battery. Let say, if seven LEDs glow, the charge available in battery is 70%. It also has features of automatic switch off the charging circuit when battery is 100% charged.

How circuit works?

The main components of 10 Level Battery Charge Indicator Circuit is LM3914, contains 10 comparators internally and is arranged in voltage divider network which basically works on circuit division rule. The battery voltage is divided into 10 parts and its output is indicated by 10 LEDs arranged in dot mode. For better usual indication different color LEDs is preferred say 3 red LEDs, 3 Yellow LEDs and 4 Red LEDs. When 10th LED glow the transistor Q1 goes in saturation state and relay energized the charger circuit is switched off and battery is disconnected from charger.

If you are interested to design your own 12V battery charger circuit then here are some links.

  1. 12V, 7Ah Smart Battery Charger with PCB Diagram
  2. 12V battery charger with over-charge and deep discharge protection.

Circuit Description of 10 Level Battery Charge Indicator

The circuit of 10 Level Battery Charge Indicator Circuit is shown in figure 1. The entire circuit of is 10 Level Battery Charge Indicator Circuit built around comparator IC LM3914, 10 LEDs and few other electronics components like resistors, capacitors, diodes, transistor etc. for working of circuit flawlessly.

10 level battery charge indicator

The battery whose charge would be monitoring is connected to B1 where diode D2 block reverse current from the circuit to battery where capacitor C1 is nothing but a filter capacitor. Variable resistor VR1 is used to calibrate the circuit for glowing LEDs at different voltage where variable resistor VR2 is used to adjust the intensity of LEDs.

Transistor Q1 is switching circuit which initially is in off state but when the battery is fully charged i.e. LED10 glows, transistor Q1 become on as a result relay energized and switch off the charging circuit. The table shown below shows the battery percentage to corresponding glowing LED.

Table 1

S.N. Glowing LED Battery charged
1. LED1 10%
2. LED2 20%
3. LED3 30%
4. LED4 40%
5. LED5 50%
6. LED6 60%
7. LED7 70%
8. LED8 80%
9. LED9 90%
10. LED10 100%

 

Calibration of 10 Level Battery Charge Indicator

  1. Connect the 15V variable power supply at B1 point (at place of battery)
  2. Set 3V to variable power supply.
  3. Adjust variable VR1 until LED1
  4. Increase voltage of variable power supply in interval of 1V per step.
  5. Circuit is ready to use.

PARTS LIST OF 10 LEVEL BATTERY CHARGE INDICATOR

Resistors (all ¼-watt, ± 5% Carbon)
R1 = 33 KΩ

R2 = 1.2 KΩ

R3 = 56 KΩ

VR1 = 10 Ω

VR2 = 200 KΩ

Capacitors
C1 = 100 nF (Ceramic Disc)

C2 = 33 µF/30V (Electrolytic Capacitor)

Semiconductors
IC1 = LM3914 (Comparator IC)

Q1 = BC558 (PNP transistor)

D1, D2 = 1N4001 (General purpose silicon rectifier diode)

LED1 – LED3 = 5mm Red color LEDs

LED4 – LED6 = 5mm Yellow color LEDs

LED7 – LED10 = 5mm Green color LEDs

Miscellaneous
RL1 = 12V Relay