Battery Level Indicator

Outline

• Introduction
• Battery Level Indicator Circuit Principle
• Battery Level Indicator Circuit Diagram
• Circuit Components
• Battery Charge Indicator Circuit Design
  • LM3914 Features
• How to Operate Battery Level Indicator Circuit?
• Battery Charge Level Indicator Circuit Applications
• Limitations of the Circuit

Introduction

I’ll teach you how to make a simple Battery Level Indicator Circuit with readily available components in this project. The status of the battery is shown by glowing LEDs on the battery level indicator. Six LEDs, for example, indicate that 60% of the battery capacity is still available.

This guide will show you how to create a battery level indicator. This circuit can be used to test a car battery or an inverter. As a result, we may extend the battery’s life by employing this circuit.

This circuit is designed based on lM3914 IC (Integrated chip). This IC is LED dot/bar display driver.

Battery Level Indicator Circuit Principle

The LM3914 IC is at the heart of this battery level indicator circuit. This IC accepts an analogue input voltage and drives 10 LEDs linearly based on that voltage. Because the current is regulated by the IC, there are no resistors in series with the LEDs in this design.

Get a sense of how the linked post – How Does an LM317-Based Automatic Battery Charger Work?

Battery Level Indicator Circuit Diagram

Circuit Components

• LM3914 IC
• LED’s -10 (Red – 3, Yellow – 4, Green – 3)
• SPST Switch
• Resistors – 18KΩ, 4.7KΩ, 56KΩ
• Potentiometer – 10KΩ
• 12V Battery (to test)
• Connecting wires

Battery Charge Indicator Circuit Design

The capacity of the battery is displayed in either dot mode or display mode via the LEDs (D1-D10) in this circuit. The external switch sw1, which is attached to the IC’s 9th pin, selects this mode. A resistor connects the IC’s 6th and 7th pins to the ground. The brightness of LEDs is controlled by this resistor. A potential divider circuit is formed by resistor R3 and POT RV1. The calibration pot RV1 is utilised here. This circuit does not require an external power supply.

The circuit is intended to detect voltages between 10 and 15 volts DC. Even if the battery voltage is 3V, the circuit will operate. This IC’s operational voltage ranges from 3 to 25 volts DC. LEDs, LCDs, and vacuum fluorescents are all driven by the Lm3914.The IC contains adjustable reference and accurate 10-steps divider. This IC can also acts as sequencer.

LM3914 Features

• Internal voltage reference from 1.2 to 12v DC.
• Programmable output current 2mA to 30mA.
• LED driver outputs are current regulated.
• No multiplexing interaction between outputs.
• It supports wide range of temperature from 0 to 70 degree Celsius.
• For bar graph display – connect 9^th pin of IC to the supply
• For dot display – leave the 9^th pin of IC

Different coloured leds can also be connected to indicate the status. Connect D1 to D3 red LEDs to signal that your battery is in the shut down stage, and D8-D10 green LEDs to indicate that the battery is between 80 and 100 percent charged, and yellow LEDs to indicate that the battery is still charging.

We can use this circuit to measure additional voltage ranges with a little tweaking. Remove the resistor R2 and connect the input to the upper voltage level. Now adjust Pot RV1’s resistance till the D10 LED lights up. Remove the upper voltage level from the input and replace it with the lower voltage level. Replace resistor R2 with a high-value variable resistor and adjust it until the D1 LED lights up. Disconnect the pot, measure the resistance across it, and replace R2 with a resistor of the same value. The circuit is now ready to monitor a wider range of voltages.

This circuit is ideal for indicating the level of a 12V battery. In this circuit each led indicates 10 percent battery level.

How to Operate Battery Level Indicator Circuit?

• Connect battery to be tested to the input of the circuit.
• Now adjust the pot RV1 so that LED D1 just starts glowing.
• Now increase the input Dc voltage slowly and observe the LED’s
• First led will glow for 1.2V and second LED is for 2.4 V and so on.

Below table shows the status of LED’s with input voltage level.

BATTERY LEVEL	PERCENTAGE	STATUS OF LED’S
1.2V	10	D1 – ON
2.4V	20	D1, D2 – ON
3.6V	30	D1, D2, D3 – ON
4.8V	40	D1, D2, D3, D4 – ON
6.0V	50	D1, D2, D3, D4, D5 – ON
7.2V	60	D1, D2, D3, D4, D5, D6 – ON
8.4V	70	D1, D2, D3, D4, D5, D6, D7 – ON
9.6V	80	D1, D2, D3, D4, D5, D6, D7, D8 – ON
10.8V	90	D1, D2, D3, D4, D5, D6, D7, D8, D9 – ON
12V	100	ALL LED’s – ON

Battery Charge Level Indicator Circuit Applications

• We can use this circuit to measure car battery level.
• This circuit is used to calibrate inverter status.

Limitations of the Circuit

• This battery level indicator works only for small voltages.
• This circuit is theoretical and may require some changes to work in practical.