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24 volt battery level indicator schematic

Battery Level Indicator for 24 Volts Batteries

This battery level indicator offers (5) LEDs that light up progressively as the voltage increases. This is a variation of the following 12V Battery Level Indicator and is a great DIY project. http://www.electroschematics.com/6868/12v-battery-level-indicator-circuit/

LED Color Charge Level
Red Power Connected (0%)
Orange Greater than 21V (25%)
Yellow Greater than 23V (50%)
Green Greater than 25V (75%)
Blue Greater than 27V (100%)
Blue full charge is about 28 to 29V

Of course, you may select your own colors if desired.

Battery Level Indicator Schematic

24 volt battery level indicator schematic

24 volt battery level indicator circuit schematic (click to enlarge)

Bill of Materials

Battery Level Indicator Circuit Operation

D1 is the voltage reference zener. Tied to this is a string of divider resistors (R2-6) that set the various fixed voltage levels. R7 & 8 form a voltage divider to that divides the battery voltage by a factor of 6. U1 is an LM339 quad comparator that compares the various voltages from the two dividers. The comparator sections have open collector outputs that simply function as switches to operate the LEDs. D7 protects against reverse battery connection.

The LM324 op amp should work OK, but the pin-out is different—and (4) LM741 op amps should also work OK.

It worked as expected and when R2 is calibrated properly, the voltage thresholds are within about 0.1V of stated values. There is no hysteresis so the LEDs tend to flicker slightly at the threshold voltages—this is not a problem.

The LEDs are biased to operate at about 1mA which is reasonably bright if high efficiency LEDs are used—mine were not of the high efficiency type. This current can be adjusted simply by varying the series resistors (R9 through R13). The overall current drain as shown is about 12mA with all the LEDs illuminated. To reduce power, a push-to-test pushbutton is recommended.

Battery Level Indicator Photos

The LEDs are old design — not too bright, but the photo does not do justice. I did not have an yellow LED and the orange LED appeared red.

67 Comments

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  • orlayodergmail-com

    Can i use this for an 18 volt Battery

  • swapra4gmail-com

    This circuit is a very informative and accurate method to monitor a battery. My concern is, i just need one red LED to glow when the voltage descends to 23.99 V from a 24.4-25 V battery and indicate that,it has to be charged right away for proper working! The battery comprises of 7 cells each of 3.7 V.
    I understand only one comparator is required, but unable to design values for the same

  • Bausomer

    Hello Mr. Keith, I’m a sophomore in high school. I’ve been very interested in electronics since I was probably 8, I was always taking apart things trying to figure out how they worked. Anywho, I am currently working on a science fair project that deals with electromagnets. I’m using 4 176kg rated holding solenoids. I’m powering them with 24 volts 2.5 amps DC, from a battery bank I’ve made consisting of 8, 12 volt 2.5 amp lead acid batteries. so far everything is working great, using the solenoids as electromagnetic climbing gear. The device I have made can support my weight and a 35 lb steel plate. not sure of the shearing force yet. however  at the moment I’m trying to improve my design by adding a battery level indicator to my device. I found the schematic you created and I’ve been trying to replicate the circuit. however I’ve ran into some problems and I was wondering if you could help me (: thanks so much

  • shivank

    Hello there i just wanted to know if an lcd displat possible in your circuit if so can you give some some outline.it would be very kind of you . thank you

  • kar

    Please can you help me if i want to use or charge and test the battery at the same time.

    And where should i connect “bat-” to?

  • venkata surendra

    Thank you sir.. That was very helpful

  • venkata surendra

    Respected sir,
    I want the same circuit to moniter 48 v battery pack.Please help me to make 48v battery pack indicator
    maximum voltage is 54v
    minimum voltage is 44v
    above 53v 5 led
    above 50v 4 led
    above 47v 3 led
    above 44v 2 led
    below 44v 1 led

  • Senthu

    using a voltage divider to pin 3 could be a solution for this. Because rest of the pins comparing the voltage less than 6.2V. Lm339 require very less power. Therefore it should work

    • senthu

      There is 49.9 k ohm resistor across the Lm339. therefore it will dorp the voltage a lot. therefore no need to worry

    • senthu

      Please the way i connected pin 3(the changes are indicated in red color). using this method VCC drop to 21V. The rest of the pins are fine.

    • Jim Keith

      But the LM339 has a Vcc pin, and the outputs may not be able to handle 42V (full charge voltage) … Per datasheet, absolute maximum Vcc and output voltage = 36V

  • Jim Keith

    There is an important issue that comes up with a 36V (nominal) version –the LM339 cannot support maximum battery voltage without exceeding its absolute maximum voltage rating. Will test and post a new circuit.

  • senthu

    SMD make no difference. before you choose any device check the required working condition (what is the amp and voltage required). because when we are using higher resister it reduces the current a lot. some devices require more current. but LM339 is fine for both SMD and normal.

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