How to Make an Automatic 12V Battery Charger




About: Hi my name is Steve and i'm a Creative and I got Technical skills i can build anything just stick to my account . I'm a YouTuber so you also can see my all videos here

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

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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



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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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31 Discussions


Question 5 months ago on Step 1

Hi Steve!

You are very creative and I bought the parts to build the simple 12v battery charger you made. However, I like this automatic one better. I do have a few questions first. Can this charge any kind of 12v battery? Can the input to the charger be a simple plug into a wall socket (no wall wart)?


2 years ago

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.

1 reply

Reply 1 year ago

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.


1 year ago

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)


2 years ago

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?

3 replies

Reply 2 years ago

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?


Reply 2 years ago

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


Reply 2 years ago

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.


2 years ago

#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.

1 reply

Reply 2 years ago

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.


2 years ago

Can a similar circuit be used to recharge using a small solar panel ?

3 replies

Reply 2 years ago

similar yes. he has the buck converter set for 13.8 VDC. if ur solar panel has between 16 and 24 Volts output then u can connect it and it will definitely charge the battery. you can also set the converter output current like he did to the max that ur solar panel will supply. you can connect it 24 hours. of course at night it will not do anything and then in the morning it will start charging again. there are chargers called MPPT chargers which are a lot more expensive, but this will do the job nicely. (The one he is using costs under $5). Dont expect too much current out of it though. the heatsinks are undersized.


2 years ago

A lot of hard work went into making this project & video-photos, well done, very good for the limited time electronics buff. Why reinvent the wheel when you can purchase the parts ready to manipulate into any project you need rather than build from scratch. Other projects I would like to see but no one yet has really considered is TINY power supplies (9v usually) for test equipment that can be purchased like 'do it your self' oscilloscope, function generator, component testers, wireless relays etc that need a 9vdc battery or 12-6v battery pack. To have these devices work on a 5vdc input boost converter or off tiny mains devices would add to their usefulness and be a nice project for hobbyists. Keep up the good work.


2 years ago

Nice instructables but the mains side is risky, you should not use XT60 on mains side but wires and connectors designed for that usage. Also you need have way to protect mains cables pulled off i.e. so no force can be applied to connected cables.


2 years ago

Terrific instructable! Instructions were very easy to follow and well laid out. A model of how to do an instructable.

Your use of existing otherwise difficult to make components is excellent and demonstrates a knowledge of electronics many electronic instructables lack.

My BatteryTender has given up the ghost and this is exactly what I needed.


1 reply

2 years ago

nice instructable.

Modern Lead Acid batteries do not suit >14V charging despite what some of the other comments say.

The correct charging voltage for the modern chemistry in a Lead Acid battery is 13.8Vdc, unless the manufacturer tells you otherwise.

The design uses a constant current pre-regulator.

That acts as a short circuit protector. It does not need another protection device.

Had this charger used a linear regulator, then it would become hot if short circuited and passing the set current into a near zero ohms load. But this charger is made up from pre-assembled switcher regulators.

They do not overheat when taken to their maximum.

I repeat, this battery charger is excellent and when used correctly will not damage modern Lead Acid batteries.

Well done.

1 reply