We already indicates state of battery using battery status indicator circuit and battery voltage state indicator using 741 IC, this time we indicate battery status in 10 different levels. 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 10 Level Battery Charge Indicator 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.
- 12V, 7Ah Smart Battery Charger with PCB Diagram
- 12V battery charger with over-charge and deep discharge protection.
Circuit Description of 10 Level Battery Charge Indicator Circuit
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.
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.
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Table 1 |
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| 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 Circuit
- Connect the 15V variable power supply at B1 point (at place of battery)
- Set 3V to variable power supply.
- Adjust variable VR1 until LED1
- Increase voltage of variable power supply in interval of 1V per step.
- Circuit is ready to use.
PARTS LIST OF 10 LEVEL BATTERY CHARGE INDICATOR CIRCUIT
| 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 |
This circuit never charge the battery, look at diode D2 !!!
The circuit posted is not the charging circuit but the battery charge indicator circuit which indicate the charge available in battery. if you are interested to design battery charger circuit there here are the link for you.
http://bestengineeringprojects.com/12v-7ah-smart-battery-charger-with-pcb-diagram/
http://bestengineeringprojects.com/12-v-battery-charger-with-overcharge-and-deep-discharge-protecting/