Simple battery charger circuit and battery level indicator with low battery recharge alarm

This is a simple 12V rechargeable smart battery charger circuit. You can use this best battery charger circuit as car battery chargers, Inverter battery charger, Emergency light battery charger etc. An automatic indicator alarm circuit also comes along with this battery charger schematic. The main advantage of this indicator is that a buzzer informs us when the battery needs recharge. This circuit schematic definitely helps for your daily life battery charging applications.Also Read:

Circuit diagram of battery charger

Batery+charger Simple battery charger circuit and battery level indicator with low battery recharge alarm
Click on the image for enlarged view

Components required

  1. Transformer (230V to 15V or 110V t0 15V)
  2. Bridge rectifier (1N4007 x 4)
  3. Capacitor (470µF, 50V)
  4. Voltage regulator IC 7815
  5. 12V rechargeable battery
  6. Diode (1N4148)
  7. LED Zener diode 9V
  8. Transistor (BC547 x 2)
  9. Resistors (10kΩ, 1.5kΩ, 100kΩ Each ¼ Watt)
  10. Buzzer (12V)

Working of battery charger circuit

  • The charging circuit is build around voltage regulator IC 7815 and two transistors BC 548.
  • The main supply 230V or 110V is stepped down using a step down transformer, and then it is rectifiered and filtered out.

Read:  Full wave bridge rectifier circuit with working explanation

  • That DC voltage is then fed to the voltage regulator IC 7815; the output will be regulated 15V.
  • 12 volt rechargeable battery is connected at the output of voltage regulator and it charges when main power is available.
  • This circuit also indicates the charging status, that is the LED1 is glows when the battery is charged (Above 10.5V).
  • When battery voltage goes below a particular value, LED1 stops glowing and the buzzer produces sound indicating that the battery has been discharged and it needs recharge.

Pin out of 7815, Diode, BC547, LED

49 thoughts on “Simple battery charger circuit and battery level indicator with low battery recharge alarm

  1. I am interested in using this circuit to simply buzz and tell me to turn on my charger…when the battery gets down to 12.4 volts.
    What would I modify to get the buzzer to go off at 12.4 V instead of the 10.5 V noted in the narrative?
    Can I simply omit everything to the left of the battery (the charger) AND can I also eliminate the unnecessary LED? I only want a sound indicator.

  2. Hello everyone,
    Am pretty new here and need some help on how to integrate a battery charging circuit to an inverter. That is, i’d like the produced power to be continious. Same AC produced by the battery will be used to charge it up for a continious supply of Ac power.

  3. Hi .
    I made this circuit, but i didn’t achive indication . In fact buzzer sounds continously whether battry low or fully charged.
    Can you please tell me the exact value of pot so that Led glows at the level of >10Volts.
    Thank you

  4. when the batteries power come downs then mz charger controller buzzer warns which i do not want, how can i staff the buzzer warns,
    thank from waiting to your reply

  5. have you ever made and test this circuit sir? i am very interested to your circuit and i just want to know and check if this circuit will not blow down. thank you

    • Hi
      For extra protection use a 10 ohm 20 watt resistor in series with the regulator output to limit the charging current.

  6. What Is The Ah. Of The “Transformer”, May I Charge 12V 9Ah Battery With The Circuit.
    Pls Reply ASAP..

  7. Sir I m very interested in doing this on my own but i want to know if i make a battery circuit to charge and inverter circuit to produce output of 230v/50hz as different circuits then tell me every time i must charge the battery separately when it is charged off am i right? or cani use relay for this to switch immeditely

  8. Dear Sir,
    Good day.
    I am planning to use this circuit in monitoring a 48 VDC battery, can you kindly provide circuit modification.

  9. I guess this circuit is good so if possible u may email me the limitation of this circuit at my email iradyregis@yahoo,com because I will use it and gimme more explanation abaut it and some summarized notes abaut a buzzer and variable resistor so thanks so much for creating dis web to help students .

  10. I have 3 basic qquestions.
    1. Can I connect this circuit in parallel with an inverter circuit.
    2. Whats d charging current of this circuit. What formula can I use to calculate it. And how can I increase it. Or better still reduce d charging time of my battery.
    3. I hope dis circuit can charge a 12v 100 or 200ah battery. Will appreciate a reply asap

  11. Hello. Please i want you to help me with a 24VDC to 230AVC inverter circuit schema integrated with battery charging circuit. And a guide on how to connect battery full and battery charging indicators. Thanks

  12. I am going to make ds circcircuit for my major project of diploma
    I have a question
    The connection of 4.7k resistor and 9 volt zener is confusing and i can not understand it
    Kindely help me soon as m wating 4 rply
    Thnxx in advance!
    Aditya :)

  13. sir,
    if we are using a 9-0-9 transformer,and we are required to charge 12v ,7 A, li ion battery
    then wt chnges should i make in the above circuits
    tell me soon plz

  14. Yes jaspreet u can use 9-9-9 transformer by eliminating its center tap
    Infact 230-15 or simply 0-15 transformer will not work as the ic lm7815 works above 18 volt so u need 2 supply above 18 volt.
    U cn check its datasheet

  15. I am trying to find information on formulas used to calculate capacitance required for a given circuit. Not a circuit in particular, just in general how to figure out what value should be used.

  16. lm7815 terminals are little confusion
    v reg means terminal 3 ( out put )
    com is gnd or terminal 2 in the practical am i correct or not ?

  17. can u pls explain the zener diode’s coonection with the 4.7k which is not given in the component list


  18. sir can u please explain… how does the indicating circuit detail..???

    it will be a greater help for me.

  19. Be aware of LM7815 requires 18V or more to produce a stable 15 Volts. With a 15V output transformer it probably produces some 13.5 Volts, which is hardly sufficient to effectively charge your 12V battery.

    Also this is a 1 Amper charger as the LM78xx chip can handle this amount of charge. 1 Amp is enough for a conditional charge of large (more than 30 Ah) capacity batteries, but will be way too low current for a depleted solar battery bank.

    Anyway, the circuit is impressively clear and simplified, can be built with a few components anf for cheap. So this is a great schematic. Thanks for publishing!

  20. Pls sir, can I use a 230, 12 0 12 center tap transformer. Is it going to work out. Thanks for ur time. Kindly acknowledge my mail

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