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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.

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    18 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…

    4. Jim Keith Jim Keith says: on November 3, 2012 at 3:18 pm

      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.

    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)

    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…

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