Battery operated heater

john April 7, 2010 36 Comments

Here is a simple heater circuit that can be operated from a 12V battery. The first part of the circuit is an astable multivibrator build around the two transistors Q1 and Q2 .The ON time of transistor Q2 is set to 0.5 S. The ON time of transistor Q1 can be varied by using the POT R2.The output pulses at the collector of Q2 is used to drive the Darlington power transistor Q3(TIP122).The transistor Q3 drives the heating elements L1 to L3.The net heat produced can be varied by  selecting the desired combination of heating elements at the output circuit sing switches S1 and S2.The net heat can be also varied by varying the duty cycle of the triggering pulse using POT R2.

Circuit diagram with Parts list.



  • The circuit can be assembled on a general purpose PCB.
  • The transistor Q3 must be fitted with a heat sink.
  • The elements L1 to L3 can be 10W heating coils.
  • The switches S1 and S2 must be able to withstand at least 5A.
  • The circuit can be powered from a 12V battery.
  • The LED D1 gives a visual indication of the duty cycle of the circuit.
  • July 17, 2015

    Like this design very much! I can recommend this to our clients, by the way, what’s the capacity of the 12V battery?

    April 9, 2015

    please provide the details of heating coil;is it available at market….?
    can we use soldering heating coil….?

  • November 28, 2014

    great circuit… and great article

  • Masoud azmel
    November 18, 2013

    Was a very nice circuit
    with this i and my freinds when nights come out home and Sit together use it and very pleasur.

  • Pinyog
    November 17, 2013

    Sir can i use this on ac to dc converted supply ? and what output is required for that and also send me the Details of Item is required for that project. (capacitor & Resistor)

  • oyinz
    October 18, 2013

    pls does any type of amp for 12v work for this circuit pls

  • oyinz
    October 18, 2013

    pls what is the meaning of the 1.5m and 4.7m in this circuit because i dont know the meaning of the m

  • Rex
    October 7, 2013

    Seetharaman, i have TIP41, can i also use it as replacements for TIP122

    • Seetharaman
      October 8, 2013

      Hi Rex TIP41 is a NPN transistor with just 6Amps absolute maximum collector current and a current gain of just 30 to 70. You have to use this with 2N3055/BD182 as darlington, of-course TIP41 in the input side.

  • Rex
    September 27, 2013

    Seetharaman, what are other replace for TIP122

    • seetharaman
      September 27, 2013

      The equivallents are MJ802, MJ3001, 2N6283, BDX54, BDX69, or simply a BD139 with BD182 or 2N3055 as discrete darlington can be used.

  • Jj
    September 17, 2013

    Up to what temperature can it reach?? pls answer..

  • September 16, 2013

    very nice popular website……
    i am live your website..
    thanks sir

    August 1, 2013

    I need a running LED circuit with speed control and how to expand the number of LED?Please send me.

  • pinky
    February 24, 2013

    Is this heater is used for heating water…plz give reply

    • Emmanuel
      April 2, 2014

      is this water heater?,can i increase battery voltage to make it more suitable larger home use? I am most grateful. Please do reaply.

      • Seetharaman
        April 3, 2014

        This is not a water heater. this is a small constant temperature chamber for calibration of rtd thermisters etc.

  • November 7, 2012

    how can run and store microcontroller pic and ATMEGA16 AND ATMEGA33 AND HOW STORE DATA IN MC.
    HOW DESIGN USING MICROCONTROLLER(89C51) TO RUN (BLINKING) 100LEDS .Please sent program in my mail.

  • Navas
    June 18, 2012

    I like this.thank you for the circuit

  • Navas
    June 17, 2012

    Good,I like this

  • Prasad.M
    March 2, 2012

    Hi is this water heater which is discussed here
    Can i use 12 V adapter to power the Circuit. If i am using 12v adapter in circuit then whats the power consumed for 1 hour/day.

    • manikandan
      February 3, 2013

      using of 3*10w coil requires 30w/hr

  • Seetharaman
    January 14, 2012

    Hi Kulwinder the battery should be connected between +12 and common ground.
    Hi Wash each heater has got a capacity of 10watts. a total of 30watts energy is available.

  • vash
    January 12, 2012

    Hey I’m building a project which involves a DC heater. I would like to find out how hot this call actually get. Thanks

  • November 6, 2011

    huy guys i have read all the circuit but i am unable to understand that where battery ‘s output nodes

  • Abd
    August 4, 2011

    thnk for your info… but i want a small battery like 12v..

  • seetharaman
    July 27, 2011

    Hi ABDS with a car battery of 40AH it will work for 12 to 24 hrs depends on the heating required.

  • Abd
    July 26, 2011

    how long this battery can survive?

  • NAM
    February 28, 2011

    Dear writer
    Just wonder who many degrees C can it provide as a maximum

  • Sabisha Suresh Babu
    July 13, 2010

    hiii how r u???

  • mouly
    June 26, 2010

    thanks very nice circuit

  • Idris
    March 25, 2010

    I really appreciate your effor. \pls kindly send me details on how to design and build 1000watts inverter/ ups

  • LEE244
    January 20, 2010

    Is this heater is used for heating water?If so what will be the output temperature ?can we use this for space heating?What is the battery back up?

  • lee244
    December 18, 2009

    Thanks very nice project but u didnt mention the current ratings of the battery to be used like 12v@10amp,12v@12ampsetc.moreover the output temperature is not mentioned

    • admin
      December 21, 2009

      I tested the circuit using a 12V,7Ah battery from my motor cycle.

  • tijani mutiu
    March 20, 2009

    Thanks for the message , but i also need the circuit diagram of 50 watt amplifier with double input and output and all neccesary information about it. thanks and GOD bless you

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