How to Make a 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 12v Battery Charge

With this charge you can charge any type of 12 v battery even your car battery

it is very necessary in cold days because battery drains out very quickly .

This Charger features 2 step Charging 1. Constant Current 2. Constant Voltage

it is very safe and stable for daily use "it's very standard "

Click Here to See The Video

Click here to see the new video

Let's Start

Step 1: Stuff I Used

  • Dc to Dc Step Down Converter - click
  • Alligator Clip - click
  • Multi-meter - click
  • Laptop charger

Dc to Dc Step Down Converter

  • it's will convert 19 volt from your charger to 14 volt to charge the battery
  • it'll provide constant voltage and constant current . ( very necessary )
  • it comes with 3 indicator led (red,blue and green) red show constant current blue show load and green show constant voltage "full charge"


  • Input voltage range:6-38 VDC (Note : input voltage not exceeding 38V)
  • Output voltage range:1.25-36VDC adjustable
  • Output current: 0-5A
  • Output power: 75W
  • High efficiency up to 96%
  • Built in thermal shutdown function
  • Built in current limit function
  • Built in output short protection function

Step 2: Prepare the Adapter

Follow the Steps

  1. Cut down the jack of the adapter
  2. Remove the outer shield with a blade (Carefully)
  3. you'll see 2 wire red and black , black is negative and red is positive (see the image)

Step 3: Connection

You can see the label over the board

  • The red wire of adapter will go to "IN+" positive of the board (see the image)
  • The black wire of adapter will go to "IN-" negative of the board
  • tight the screw terminal with a screw driver

Now connect alligator clip

  • Red alligator clip wire will go to "OUT+" Positive of the Board (see the image)
  • Black alligator clip wire will go to "OUT-" Negative of the Board

Step 4: Configuration

Now you need a multi-meter to set it up

  • Plug the power to the adapter
  • Connect the black alligator clip to negative lead of multi-meter and red alligator clip to positive lead
  • you can see 2 Potentiometer over the board (see the image)
  • first one is voltage and second one is current
  • Now select the DC voltage reading on your multi-meter and turn the Potentiometer with a screw driver until you get 14 volts reading on multi-meter
  • Now select the Current Reading on your multi-meter and turn the second Potentiometer with a screw driver until you get 2 amps reading on multi-meter (you can go up to 5 amps all it depend upon the battery capacity if you have a bigger battery "like a car battery you can go up to 5 amps "

Step 5: You Are Good to Go

Just plug the red alligator clip to positive of the battery and black alligator clip to negative of the battery

and plug the power to the adapter

You'll see blue led will glow there it means it is charging If you see green led glows after some time it means the battery is fully charged

If You see Red led with Blue led that means it is in constant current charging

Click Here to See The Video


Thank you for visiting my Instructables

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    31 Discussions


    10 months ago on Introduction

    Most batteries require an unstable (cyclic) charging rate or the battery will develop Dendritic growth and self discharge. How does your charger avoid this issue?

    1 reply

    Reply 4 days ago

    You are correct lead-acid cells have to have a cyclic charge and not a steady charge...once lead-acid batteries are charged without the benefit of cyclic charging..over time they will self discharge /not hold a charge at all.


    14 days ago

    Bro i need charger for 6v battery


    Question 8 months ago

    I bought two of these modules but didnt worked for me. I only see green light when connected to battery.


    10 months ago

    I'm surprised @instructables let this fly for so long...


    10 months ago

    Excellent bro

    laith mohamed

    10 months ago

    I must make one , thank you for sharing .


    Question 10 months ago on Introduction

    Can I have this plugged all the time charging the battery and also an arduino plugged on this battery acting as a nobreak for my arduino?


    2 years ago

    You can use a 12V light bulb if you don't have a DC to DC converter.

    2 replies

    Reply 1 year ago


    Connecting the Amperimeter to the output will burst the XL4015E1 IC or Multimeter.

    It seems to me another video to sell the regulating boards, these boards only regulate the Volts, if placing the meter in series with the battery only gives a maximum of 400mA, even with an Industrial Well of 12.5A Mean Well 12VDC.

    Turning the potentiometer knob W 102 does nothing ...

    It sucks this board.


    Question 1 year ago


    Connecting the Amperimeter to the output will burst the XL4015E1 IC or Multimeter.

    It seems to me another video to sell the regulating boards, these boards only regulate the Volts, if placing the meter in series with the battery only gives a maximum of 400mA, even with an Industrial Well of 12.5A Mean Well 12VDC.

    Turning the potentiometer knob W 102 does nothing ...

    It sucks this board.


    Question 1 year ago


    Is this load controller limited to 5A maximum sources?

    Can I connect this load controller to a 12VDC and 12.5A Industrial Mean Well?

    You will not burst the IC XL4015E1?

    Thank you and congratulations.


    1 year ago

    Request your advice - I keep a spare 12 volt SLA battery in my car. Been looking for a way to charge it in the car. Do you see any issues with an approach that would use a boost converter off the 14.4 alternator voltage as power supply for the step down converter for charging? It seems cleaner than inverting the car power to 110 volts AC to provide power to a lap top charger. Is there something I am missing?


    1 year ago

    I made it.

    Warning! Be sure to connect your power source to the board BEFORE you connect the battery! If not it will release the "magic smoke" inside :) and will not work anymore!


    2 years ago

    Hey just a heads up your charging sealed lead acid batteries with a lithium charger that cost 1.96 cents. Now arguably there are chargers that can recognize between battery chemistries but even the cadex I use to analyze balance and charge multi cell banks cannot and must be programmed differently for each and I mean it's overkill as far as charges go.

    In basic terms each chemistry of rechargeable battery has a unique charge and discharge cycle.

    lithiums being the happiest out of nickel metal hydride / nickel cadmium and sealed lead acid as far as being fully depleted and then recharged makes them better for items which will die fully between charges as well as for items that must be recharged from many different states of charge. Be that half dead or dead for a week.

    Without getting into the theory too much the gist of what I'm bringing up is sealed lead acids may not necessarily be charged most effectively with a lithium battery charge curve.... nor is it necessarily the safest way to do so, same as how a lithium drill pack can't be charged safely on a cheap nickel metal charger, because the charge curves are wrong for the different chemistries....

    there are specific chargers for specific chemistries and I'm afraid that the 1.98 charger advertised for lithium may not be the best choice for your application. Do not put it in your car please.

    In this case hopping chemistries while adding a multi stage charger isn't actually adding much as far as safety measures go. Sealed leads would prefer constant voltage than ramped voltage, utilizing constant amperage up until a full charge would be a better move, then at full charge all that needs to happen is a switch from full to float or trickle charge. if I'm remembering properly. See a lithium pack charger increases voltage incrementally, not necessarily the best for a SLA.

    Take a peek online looking up different charge curves and I bet you'll catch what I mean real quick. Still for all intents an purposes good one for making something to fix your problems, right on. Just thought you could use the advice if you were wondering what the deal was with that SLA now that he's been on that charger.

    Take note using your multi meter the next time you choose to you use your set up, read the battery before applying charge and then watch how the charger attempts to charge the battery. SLA would really benefit from a higher voltage than what is desired being the original charge voltage. For example 14.4 volts from an alternator to your car battery. When the battery is low, I bet the charger will recognize the voltage and begin by applying a lower voltage than the battery is rated for. This and this alone is enough to damage the cells, that's why I came to tell you. Anyway best of luck to you

    3 replies

    Your comments are well taken, however, it's not clear they apply here. If you look up the chip and board the OP is using you'll learn more. The part about 'lithium charger' appears to only be "marketing". Technically speaking, the little board isn't actually a 'charger' per se. It simply could be used to MAKE one of those. But I expect the seller gets more hits when that appears in the title! Other vendors of the same part leave out those marketing buzzwords.

    This is the component on the board which is just a regulator, not a charge controller:

    So it appears to be a voltage and current regulator, i.e. it applies the configured voltage up to a maximum of the configured current. So from a charging standpoint, I believe it works as a current limited (not controlled) constant voltage charger. As I have not found the full board schematic, this is a still an educated guess - but the chip itself is sold as a regulator NOT as an intelligent charger chip.

    You are right to be concerned about properly matching battery chemistry to charging approach. Many thanks!

    I've done some more digging and found some videos of people playing with this board. One of items lists the additional parts on the board - an op-amp and an LM317 regulator. But still no schematic.

    I bought a couple of these and found that when connected to a gel-cel (SLA) and set for an appropriate max current, it kept the voltage constant but the current draw went down as the battery charged.


    Reply 2 years ago

    I have several of these little PSU's, they are general purpose step down PSUs (some provide step up/down). At the current supplied, charge curves will make little difference. SLA used to be used in older motorcycles with the crudest of chargers.

    I use the bigger PSU of this type to supply a steady current to my Li-Po charger ;)

    The voltage should be set to 13.8 V (not 14V) for lead acid charging. I'd also set the current quite low as the charger may not cope at higher currents. As the voltage reaches the set voltage, so charging will of course diminish. It's not ideal but is probably more accurate than may mains car battery chargers and at least as good, if not better as those used in burglar (12V) and fire (24V) alarms. In an emergency, for a few pennies, who really cares? In the past I've charged Ni-Cds via a length of co-ax cable with a car battery charger ;)

    In addition, this unit will charge a "flat" battery, whereas many of the "electronic" car battery chargers will refuse to supply a charge if the battery voltage is "too low". So useful to get some charge into the battery.

    I have to agree elsewhere, it's more of a "how to assemble" rather than "make", little more than stripping wires is shown - however still useful to those that don't know.