Simple Emergency Light Circuit with Automatic Charger

Some of our readers requested for Emergency circuit with charge controller. Here I’m presenting  such kind of a circuit diagram with automatic charging.It is very easy to implement on your home and work areas.Our circuit is capable of turns on the light automatically when power failure occurs and turn off if main supply is return.LEDs are used as emergency light bulbs in this system, The important specialty of this Emergency circuit is an automatic charge controller which recharge the battery if the voltage is below the threshold level and cut off the charging supply to the battery, if the voltage reach at the pre-set level, two LEDs are used to indicates the of presents of main power and activation of charger.

This circuit mainly focus to lead acid battery life, in this circuit design we limit the maximum charging voltage is 13.8V as per lead acid battery manufacturers.

Circuit diagram of Automatic Emergency Light

Emergency circuit with charger Simple Emergency Light Circuit with Automatic Charger
Click on the image to enlarge


  1.  IC 555
  2. Transistor BC 548
  3. Diode (6A4 x4, 1N4007x2)
  4. Zener diode (5.1V)
  5. LED (red, green, white)
  6. Capacitor 4700μF, 25V
  7. Resistor (1KΩ x 3, 820Ω, 5Ω 10W x 2)
  8. Variable resistor 10KΩ
  9. Relay (12V, 10Ax2)
  10. Transformer 230V/0-15,5A

Working Automatic Emergency

  • The main component of this circuit is 555 timer IC which control the automatic charger circuit.
  • Two 12V relays are used to switch the charger and emergency LED lights accordingly.
  • Consider the main supply is on, then the step down transformer reduce the ac voltage level to 15V AC
  • Bridge rectifier converts this to 15V DC and 4700μF capacitor remove the ac ripples to make a perfect DC.
  • Green LED indicates the presents of main power, 1KΩ resistor used as current limiting resistor for LED.
  • The relay connected to the LED is always ON if the main power is present, so the LEDs are remain in OFF since those are connected to NO (Normally Open) terminal of the Relay. (Read our Relay connection diagram to know more about Relay connection and configuration)
  • The variable resistor is meant for set the voltage level for the charger activation, a 5.1V Zener diode is used to turns off the charger circuit if the battery voltage reach at 13.8 volt which helps to Lead Acid battery’s long life.
  • Negative terminal of the lower comparator is connected with battery voltage to compare the battery voltage level is below the pre-set level (voltage level to ON the charger can be set by varying the variable resistor).
  • If the battery voltage reach at below the pre-set level the lower comparator will reset the flip flop in the 555, which turns ON the charger.
  • The battery is also connected with positive terminal of the upper comparator, which checks if the battery voltage level is 13.8V, then it sets the flip flop and thus turning OFF the charger.
  • LEDs provide long life, because LEDs drawn very low current which depend on the number of LED connected in parallel.
  • At the time of power failure all the charger circuit will inactive and the relay RL2 connects the battery to LEDs, thus it glows.

Components pinout

29 thoughts on “Simple Emergency Light Circuit with Automatic Charger

    • Hi Vinod,

      Nice to see you here. Function of 10W resistor is to limit the charging current of battery, you can replace that resistor when using 0-14V regulated power supply.

  1. my doubt is, The life time of the battery in the automatic charging emergency is lesser than recent using emergency??it is correct??

    • It has been already mentioned in the working points.

      -The variable resistor is meant to set the voltage level for the charger activation, a 13.8V Zener diode is used to turns off the charger circuit if the battery voltage reach at 13.8 volt which helps to Lead Acid battery’s long life.

  2. Hii
    pls confirm in the list its mentioned 6A4 required 4 in nos whereas in drawing it only 4 are used.
    pls confirm if u missed any diodes as in a simple battery charger its shown all 5 diodes are used

  3. Thank you wonderful circuit design. I built this at home to lit up during the power failures. I am facing the couple of problem.
    1. Not able to find 13.8 V Zener Diode. So I used 12 V Zener Diode. Will this limit battery charging to 12 V?
    2. How to adjust the 10K pot to trigger the charging circuit?
    Thanks once again. Your help in resolving this issue will be of great help.

    • Hi Ajish
      1. You can connect 5.1V zener, and set the pot. battery charging limit can be set by adjusting pot.
      2. You can use a Digital voltmeter and a variable voltage source (use pot to vary the voltage).

  4. Hi,
    I would like to know which will act as a comparator in the circuit and also would like to know the importance of 555 timer in the circuit.

    Thank you

  5. Dear Sir,
    Its very simple circuit diagram, can u explain what changes require if using 6 volt battery,
    which value of fix resistance require than 10K variable resistance. and value of Zener diode.

  6. thanks it is a nice circuit , pls can I replace the transformer 15 v 5A , bridge and C4700 with 15-17V 750mA adapter becaus I’ll use this circuit to charging 12v 7Ah SLA battery (I’ll escape leds)

  7. What types of white LED’s can be connected, and how many? I have two of “G4 LED 26 SMD 3528 Warm White Light Car Marine Boat Bulb Lamp 12V 668 GW4326″. Could I use these and/or other LED’s. Is there any kind of limit to the LED’s other than those created by the battery? Speaking of the battery, could I use a 7Ah 12v gel cell battery? If yes, would this charger circuit work with this battery?
    Thanks, a lot, in advance.

  8. I am retired and for hobby purpose I am learning to make small projects.
    I found this “Circuit diagram of Automatic Emergency Light” is simple.
    I tried to make it on general pcb but failed. If PCB is available for this, Please quote for that.
    I am interested to purchase 5 pieces of the same.

  9. i have one doubt maximum how many leds are use in this circuit? if i use 30 leds what will be the changes in the components????????
    please reply sooooooooooooooon…

  10. 12V relays are used to switch the charger and emergency LED lights .
    what is his Model number bcz i use the electronic work bench there is no 12v relay so plx tell me the model no like this
    EDR201A12 .

  11. Hi. I made the same circiut but when I adjust the pot. it is charging the battery. But when ı make the threshold value low and cut off ac source the light relay doesnt work. The other problem is that when I cut off the AC source the current flows on TH and the red light glows. and the 55 is heating. How can I deal with these faults.
    Thanks so much to help me

  12. Sir.
    Circuit drawing resistance 10ohm 10 watt but equipment ‘s resistance 5ohm 10watt.
    Please tell me what type of resistance I used in circuit.5 ohm/10 ohm??

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