12 Volt Zener Regulated Charger

12V Voltage Regulated Charger

Most of the battery chargers do not have current and voltage regulation provisions. The step down voltage is simply used for charging. These chargers develop internal resistance so the output voltage drops when the battery is connected to the charger. Moreover, fluctuations in the AC line also affect the charging process. This current and voltage regulated charger eliminates these drawbacks and can provide well regulated 12 volt DC for charging.

0-15 1 Ampere step down transformer drops 230 volt AC into 15 volt AC which is rectified through the bridge rectifier comprising D1 through D4. The rectified DC is then made ripple free by C1 and send to the collector of the medium power NPN transistor T1 to give regulated output. Resistor R1 and Zener diode ZD are used for both voltage and current regulation. Output current from the emitter of T1 depends on the value of R1 which can be changed according to the requirement using the ohms law.

12 volt Zener diode gives constant 12 volts to the base of T1 so that output voltage remains 12 volt irrespective of the input fluctuations. Diode D5 is polarity protector that prevents short circuiting if the polarity of the battery is reversed. LED indicates the charging process.

Voltage Regulated Charger Circuit Schematic

12 Volt Zener Regulated Charger

12 Volt Zener Voltage Regulated Charger Circuit Schematic


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  • Colin Mitchell

    The output of this circuit will be less than 11v and will never charge a 12v battery.
    There is no point in smoothing a voltage when charging a battery as a battery charges much better when spikes and pules are present. These spikes break down and dissolve sulphation.
    D. Mohankumar’s circuits never work and he should not be allowed to put them on the web.

    Colin Mitchell

    • cezar


      I think this is not intended as a fast charger or an efficient one, but left constantly as a trickle charge on a standbay battery, this one will do, I just don’t think that a one amp. is appropriate, perhaps 0.5 amps will do more justice when it comes to heat considerations.
      This is a basic configuration for a boosted zener regulator, if the transistor rating is exceeded , for the application, this will be another “Smoke on the Water” :))


  • rahil

    Dear MOhankumar ji, i m in need of help from an expert of electronics and especially automobile ignition electronics.I want to build a contactless ignition which will sense from trigger pulse coil and use transistor for switching to ground to coil and positive will be direct from battery as you may see here a thread started by me ( ) it wil be a great help if i can get some help from you if possible. Thanks

  • rudik

    This PSU circuit is good, but would be better if we change the zener diode with 78xx IC. Others, to dumping up the current flow through TIP122, you may leave at as schematic above, then use output to drive 2n3055.lets say 3055 will deliver 1 A each, so you need to 5 pcs of 2n3055 in paralel configuration, dont forged to add 0.1 ohm/5 watt chalk resistor to emitter as output,don’t forged to place it in proper alloy headsink to dissipate the heat.

  • peter

    waitting for your reply.

  • peter

    can this be use to charge 12V 200ah deepcycle battery

  • arif


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