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    This is the circuit of a simple 12 volt battery charger for Lead Acid battery. It gives 12 volt and 5 Amps current for quick charging of the battery. If the battery is partially discharged, full charge will be attained in one hour.

    The circuit uses a 0-14 volt 5 Ampere Step down transformer and a 10 Amps Bridge rectifier module to convert AC to DC. Since pulsed DC is good for Lead Acid battery, a low value smoothing capacitor is used as C1.To monitor the charging status, Ampere meter is provided in the positive rail. LED act as the Charger on status.

    Schematic of the Simple 12 Volt Battery Charger Circuit

    12v charger

    When the output is connected to the battery terminals, the meter shows a higher reading depending on the current flow into the battery. As the battery attains full charge, its terminal voltage rises to 13.8 volts and current through the meter ceases. The meter reading then returns to zero. This indicates the full charge state and the charging can be terminated.

    attentionThe author D Mohankumar is not an active member anymore. Please take into consideration that the presented information might not be correct.
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    48 Responses to "Simple 12 Volt Charger"

    1. has anyone tested this?
      does it work?

    2. I’m using the same trick but instead of using 14V trafo, I used only 10VAC. So if it is converted to DC (10 x 1.41) it will approximtely convert to 14VDC which is still in controllable range. Ammeter could be replace with voltmeter too but must be parallel connection.

    3. hi, can anyone explain why ammeter is needed and is it possible for the circuit to work without the ammeter… thanks in advance…

      • precious says: on August 12, 2015 at 2:31 pm

        The ammeter is used for knowing the current output that is the current given out by the charger circuit to the battery.

    4. It will work fine without ammeter, but the ammeter provides a good means of telling when the battery is charged because the current drop off greatly.

      You can make your own ammeter by placing magnetic compass next to the wire and observing deflection.

      Or you can buy an inexpensive DC “clamp-on” ammeter at your auto parts store –I have on that I use all the time. The insulated lead simply is place into the slot.

      • piyush patel says: on January 12, 2015 at 1:29 pm

        Dear sir,

        i making 12v/12ah battery charger with auto cutoff (14.4v) using 1.5a transformer Please suggestion and send me the circuit

        thanking you in advance

    5. This circuit works but why the 100 microfarad cap? Make you secondary 10 volts and it will not “cook” your battery due to overcharging. I did this with unattended industrial units and this was the most reliable.The batteries were on a battery operated fork truck and the transformer used was a 500 watt unit charging 180 ampere hour batteries for over 10 years. The batteries lasted a lot longer than on a electronic controlled charger 3 years instead of SIX months!!(With stacks of I.C’s and some with Microprocessors)

      • jwzumwalt says: on May 12, 2015 at 3:45 am

        The output of the bridged diode is a full half wave ripple. The capacitor removes ripple.

    6. hi, i tried this circuit with a 15v, 1A center-tap transformer, the transf was superhot. i guess d power rating is low so, can i use a power trnsistor to boost d current from d transfmer output? Thanks in advance.

      • if you use a center tapped transfo ,the centertap should be grounded and two diodes should be used instead of the bridge.

    7. how many turns of transformer plz say all deataild any on

    8. hi, how woul i know if the battery is fully charged? any indicator

      • Hi Israel
        The battery if it is an open type with liquid electrolyte it will appear as if the liquid is boiling then it is fully charge without instruments. If you have an hydrometer then you will be able to test it . You draw some of this liquid or acid into the syringe and then you check the float inside that it drifts on the acid at the bottom of the level you can read now how strong is the acid it will be for a “Healthy” then the reading will be 1,240 to 1,280 Some manufacturers make the the acid stronger but it is rare. Return the acid in your hydrometer TO THE SAME CELL AND REMEMBER IT IS SULFURIC ACID WASH THE HYDROMETER IN WATER AFTER USE!!! NEVER USE CALCIDE, BAKING SODA OR ANY ALKALI ON THE TOP OF A BATTERY TO CLEAN IT ONLY WATER. The voltmeter method is switch the charger off wait a while say 30 minutes and then read the voltage of the battery In this state the voltage should be 2,3 volts per cell roughly If you have a 12 volt battery then the voltage will be 13,8 volts or there about

    9. I’ve made the same one but I couldn’t find 14v so I got 15v tranfo instead. The off load voltages were 22.7 and 14 when the battery was connected. I also added a 6amp diode on the positive side with battery in series to avoid overcharging.
      but I was wondering if I could add a battery charging status meter as well to monitor if the charging is low or whether its fully charged
      like some kind of led meter may be two leds one green n one red so when the battery is low red wud turn on n when its fully charged green wud turn on
      plz if anyone can help me with this contact me on Facebook @HaZZanZia or msg me on my page I’ll add them
      I connected this whole setup with my WiFi router with a 3 three way switch to make a small UPS kinda thing so in power outage I can still be able to use internet

    10. Which diode shall i use with when using cntre tap transfo.

    11. Sir i hve 10A diode. Can i use that. And pliz tell me how to use centre tap transformer in this circuit.

    12. I used an old 12V battery charger that was not working. One or more of the original Diodes was no good.
      I used the original case, transformer, ampmeter, fuse bridge and connecting leads.
      Then followed the diagram above.
      Working well now. Good article.

    13. sir,which type of capacitor u used in this ckt……….could u plz tell me??

    14. can i use a 15v transformer and is it only for a lead battery alone?

    15. A 15V transformer will overcharge the battery. OK, if you monitor the voltage while charging and disconnect at 14.5V or so. Also monitor the transformer temp with your finger as the current may be excessive and cause overheating.

      Not recommended for other types of batteries, but may work to a degree…

    16. I need a circuit for 12v 5Ah lead acid battery charger cicuit without transformer……

    17. Thilak There only one solution to your problem and that is a solar or wind or petrol generator. Transformerless chargers will have to be switchers and if you are a amateur or beginner then you stand one foot in the grave and the other on a banana peel!

    18. sir I have 5amp transformer but it has three out .so how can I use bridge diod connection with this .
      Pls help me sir.

    19. Sir i need a charger for 12v 150ah lead acid battery

    20. pls sir can this cct also charge deep cycle battery effectively

    21. please sir i want to design a 12v 75 ah battery charger, just give me tips on how to build it.

    22. sir i want to know if this charger will well for dry cell battery

    23. sir i want to know if this charger will work well for a dry cell battery

    24. where should i put an on off switch?

    25. The LED lights up and depletes the battery when the mains plug is not connected.Is this normal?

    26. LED will keep on lighting after you widhdraw the leads from mains plug..

      So a little modification is needed ..
      Put a diode b.w the resistor and the ammeter in place of short wire.

    27. I connect an 12volt 4ah battery and the ammeter shows 3 amperes!I don’t think that’s normal.The battery has max input current less than 1,2A

      • Arxomastors hi! The current into your battery is controlled by the state of charge of your battery and the power output and voltage of your charger. A lead acid battery will take what you throw at them (within reason) The charger you need will need a series resistor to limit the current. I fitted a 12 volt 18 watt globe in series and then your will also indicate that you are charging. This is the cheapest and easiest way to limit the current.

      • arximastoras says: on June 14, 2015 at 1:16 pm

        Thanx for the reply.A couple of questions more if you please.How much should the voltage measure at the output without a load? Also,my transformer is 15 volts.What modification is needed to avoid overcharging the battery?

        My battery has these specs:
        standby use 13.6-13.8 volts
        cycle use 14.5-15.9
        max initial current less than 1.2A

    28. Please any can help me, i want to do this without using transformer…

    29. can I use 15v/2A transformer replace of 14v/5A transformer….

      • Jan Zumwalt says: on July 29, 2015 at 12:22 am

        No you can not.

        When trying to charge a 12v battery, the charging voltage must be greater than the battery or the battery will drain towards the charger (high to low). Also there is some voltage drop across the bridge diodes so the circuit already has a marginal supply voltage. Many similar charging circuits use a 16V transformer supply.

      • Jan Zumwalt says: on July 29, 2015 at 12:25 am

        I am sorry, about the previous answer – misread the /2 as “12”. The 15v is acceptable but it will only charge at 2A which really does not “charge” it is more like “toping” off the battery.

    30. pls hw may connect ammeter to a battery charger and the substitude if it is not available

    31. Sir, I build my own circuit with 15 volts transformer and 4700uf/ 25 volts capacitor . I want to know if is ok, if it has no bad effect on the battery thanks sir in advance.

    32. There were not very many diagrams. I’m looking for a diagram of a Linwood MP8 battery charger. The wiring on it was like a rat’s nest and it used 3 amp diodes which were running at their limit. The circuit allegedly produces 6 or 12 volts by operating a switch. Another switch gave High or Low output. Its this last bit which is puzzling as I’m not sure whether “Low” was achieved by putting the extra diode in series with the output or by going from full-wave to half-wave. When I took it to pieces it all seemed so simple but its not!

    33. I’m using centre tap transformer of 18v/2amp and bateery of 12V/7.5amp. Using these equipments will the circuit work?

    34. v sambath kumar says: on April 8, 2016 at 1:56 pm

      Hi Riyagote,

      Actually i want to post a project for 12v 7ah bat charger ,this is a tested and found working ok circuit.Try this make sure you go for a 15v 2amp transformer.



      V Sambath Kumar

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