How to Make an Automatic 12V Battery Charger





Introduction: How to Make an Automatic 12V Battery Charger

Hey! everyone My name is Steve.

Today I'm going to show you How to Make a 12v Battery Charger

Click Here to See The Video

Let's Start

Step 1: Features

Input Power

  • 110-220 v AC

Output Power

  • 1.25-24 v DC Adjustable at 8 Amps

Built-in Protection

  • Short Circuit Protection
  • Over Load Protection
  • Over Charge Protection

Charger Features

  • Constant Current Charging
  • Constant Voltage Charging
  • Full charge indicator
  • Charging Indicator

Continuously asked Questions

Q - Can I leave it overnight

A - Yes! For Sure this will not overcharge your battery just because we're using constant voltage there will be no potential difference to make your battery overcharge

Q - Why you are setting the voltage to 13.8v

A - Just because when a 12v battery get fully charged the voltage is 13.8v Google it for more information

Step 2: Gallery

Step 3: Things You Need




Step 4: Stand Off Installation

  • First, install the standoff "as shown in the image "
  • Do the same for SMPS and DC to Dc Convertor

Step 5: The Acrylic

  • First, pull off the protective layer from the acrylic sheet
  • Now place your components " as shown in the image "

Step 6: The Drill

  • Now use a marker to make the point for drill
  • Now use a 2mm drill to drill the holes
  • And now go for 3mm drill bit and at last counter shink all the holes " as shown in the image "

Step 7: Assembly

  • Now use some screw to screw the board with acrylic sheet " as shown in the image "

Step 8: Wiring Diagram

Step 9: Wiring Part 1

  • Now solder the XT60 with Ammeter with some wire " as shown in the image "
  • And then use heat shrink tube to secure the connection

Step 10: Double Sided Tape

  • I used some double-sided tape to hold the Ammeter and XT60 Connector

Step 11: Wiring Part 2

  • And I Passed all the wire underneath the board till last and connected it to the converter output" as shown in the image "
  • And now I took 2 wire along with ammeter wire and connected it to the output of SMPS " as shown in the image "
  • And now I connected the ammeter wire and passed all the wire underneath the board till last and connected it to the converter Input

Step 12: Output Wire

  • I used XT60 connector with 2 alligator clip and wired it together and used some heat shrink to secure the connection

Step 13: Input Wire

  • I used XT60 connector and connected it to the Green connector for mainline input " as shown in the image "

Step 14: Final Assembly

  • I used couple of screws to close the upper acrylic sheet
  • And used some rubber feet on the bottom

Looks neat

Step 15: Calibration

  • Now connect the main input wire
  • In order to set the current, you need to short the output wire and now set the current with the potentiometer " as shown in the image "
  • now you need to disconnect the output wire in order to set the voltage and now set the voltage with the potentiometer " as shown in the image "

My Settings

  • Set the Voltage to 13.8v
  • And set the current to 1 Amps or more it depends on the battery size

Find out the current

  • Use this formula - Battery Capacity x 1/10 = setting


  • I used a 7 amp battery, now let's put the formula
  • 7 x 1/10 = 0.7 and here I set it to 1 amp " You can go for little higher current but not too much "

Step 16: Finishing Up

  • Now just plug the battery and it's all set
  • You can see the ammeter it's drawing about 1A just because we have limited the current it is the safest way to charge the battery
  • And when the battery will get fully charged " This will automatically stop the charging " Just because we have limited the Voltage and there is no potential difference to overcharge the battery


  • Red Light - Charging
  • Blue Light - Full Charged

That's all for today guys!

Click Here to See The Video

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We have a be nice policy.
Please be positive and constructive.




Dude! What about safety? You almost touched the AC DC power supply!

Also I am not sure the XT60 rated for mains voltage. Input and output connectors are easily interchangeable and with human error you blow up the whole thing.

Cover the sides with plastic too, in this form is lethal.

The whole unit could be tucked into a smallish plastic project-box fairly easily. But I agree, use a mains AC rated connector for that side.

mmhhh this work,but if you disconnect (for some random reason) the main power,the battery current flow into the step down converter,one diode (6a10) connected -out to cathode and anode to -bat resolve that problem (risk of melt wires if not)

I own a 1963 model Royal enfield bullet and want to use this circuit. I want to have two batteries and want to charge both of them (may be one after another). what modifications are needed to this circuit?

I am familiar with the Enfield rifle, but what the heck is a 1963 Royal Enfield Bullet? i am assuming it is a battery but why the Titile?

If I were you, I would have quickly google it. It's a motorcycle manufactured in 1963

It should not make a difference with two batteries in that each will only float to its own individual requirement. That being said I am assuming you are running both in parallel and not in series.

why do you guys keep praising this guy.... this is not a charging circuit this is just a lab power supply.. you can buy online that he added a volt meter display and a another circuit that is not needed.. this has no intelligent power management meaning its dumping 13.8 volts in and its over filling with amps think of a glass of water unless you shut off the current when it stops taking a charge and reaches that 13.8 volts this is done with math and a ic logic circuit... similar to lipo chargers but charge is on for 30 seconds then off on then off...

so this is just another instruct able by an indian guy thats wayy dangerous..

im not trying to be a jerk just showing you all the truth.. reason he put a volt meter display is to watch the voltage get to a set point then shut it off if you forget or walk away .. ever see a lead acid or glass mat explode.. its not pretty and it explodes with the ammount of force of a grenade..

you need a circuit that goes from full charge to top off to trickle then float.. and to do this you need inelegance that is nothing more than a lab supply... so stop praising him it should be removed from this site

#massimostep is correct up to a point. On the side of your battery you can see "cyclic use 14.1-14.4V",that is for deep cycle use. What you are doing at float charge (13.8V) is ok for say, a UPS for a raspberry pi, if you only unplug it for 5 minutes to plug it in somewhere else. You haven't taken more than 5% out, so you don't need absorption charge at the higher voltage. If you ran the pi all night you would be deep cycling the battery. Then 13.8V would only take the battery to about 80%. Batteries used like that might last 6 months then die. You might manually turn up the voltage till the battery voltage has been at 14.3V for half an hour. Note that due to voltage drop in the cables, what you see on your display will be higher than the voltage at the battery until the current comes down.

Nice instructable, nice production.

what he sees on the display will be what the battery is getting. at 14 volts there is hardly any current flowing into the battery so the drop on the wires is minimal. no more than a few 10's of millivolts. but yes it is a good idea to top it off at 14.3 volts once a week.