How to Charge a 12v Battery Without a Charger

Do you ever of charging your car battery without a charger? Charging a car battery is actually possible, and there are multiple ways to do it. Today we will let you know different ways of charging a 12v battery without a charger.

12v batteries or car batteries have a specialized charger to charge the batteries. But sometimes you can get caught situations where you will not get access to a charger. In such a situation knowing how to charge a 12v battery without a charger will be very helpful for you. Keep reading this article to know how to do it.

Using another 12v Battery

If the 12v battery you need to charge is a car battery, then the easiest way to charge it is using another 12v battery. You can quickly charge the battery using another 12v battery of a car. For this, you will need access to another vehicle with the same battery, which is upright. Besides, you will require a car jumper cable to connect both of the battery.

At first, start with parking both of the car in a safe area. Make sure that both of the vehicles are turned off and the parking brake is turned on. If you are in the middle of a road, then we will suggest you park the vehicle on the right side. Make sure that both of the cars are front-facing while parked. 

Take a closer look at the nearby area. Make sure that there are no fire flames or smoking nearby the cars to ensure proper safety. Now take the jumper cable that you choose. Make sure that the cable is on a good condition and suitable for the vehicle.

Now connect one of the jumper cable’s positive clamps, which is marked red with the positive terminal of the weak battery. The positive terminal will be signed with a “+” sign or a “POS” sign. Now attach the other positive clamps with the donor battery’s positive terminal. Now give a careful recheck and make sure that all the connection is properly made.

Now wait for a while and then start the donor vehicle. The car battery should be ready for use. If not works, then try for several times. The above procedure is for waking up a dead battery. Not for fully charging the battery. This procedure can jump start your vehicle immediately.

How to Make a 12v Battery Charger

You may not think about the possibility of making your car battery charger. It is possible to make a 12v battery charger. Below, we will discuss the step by step procedure of creating a 12v battery charger using only a few types of equipment. You don’t need any technical step for this procedure, but you will need to follow the steps carefully:

You will need the following item for the process:

  1. DC to DC step down converter
  2. Alligator Clamps
  3. Multi-meter
  4. Laptop Charger

You can find these items at any hardware shop nearby. You can use an old but working laptop charger for this purpose.

Prepare the adapter

Cut down the jack from the adapter a cutter. Now remove the outer shield with a sharp blade. Under the shield, you will find two-wire colored black and red. The red-colored wire is positive, and the black colored is negative as usual.  

Connect the cable with converter

The dc to dc step down converter is a circuit which allows you to convert the actual voltage of the charger to 14v so that you can charge the battery. It will also show you the constant current and constant voltage. It includes three indicators, which are colored green, red, and blue, to confirm the charge measurements.

Now give a closer look at the label of the circuit board and find the “IN+.” It is the positive point of the board, and you need to connect the red wire with it. Also, find the “IN-” cable which the negative point of the board, and you will need to join the negative or black wire of the charger with it. 

Remove the screw from the positive and negative terminal. Then connect the wire accordingly as we mentioned above. After that, put the screw back and tighten them. Now you will need to connect the alligator clamps. You can get them any auto or hardware electronic shops.

First, find out the “OUT+” and “OUT-“ point on the circuit board. Usually, they will be on the opposite side of the “IN+” and “IN-” point. You will need to connect the positive clamp or the red clamp with the positive terminal or the “OUT+” terminal. And, the negative wire or the black cable with the negative terminal or the “OUT-“ terminal of the circuit board. Connect the clamp as like as before by removing the screw.


Now connect the adapter to the power source of your home outlet. After that, you will need to connect the alligator clamps with the battery. Connect the black or the negative clamp with the negative lead of the multi-meter and the positive clamp with the positive lead of the multimeter.

Give a closer look to the board again. You will see two potentiometers on the board staying together. The first one is for voltage, and the next one is for current. Now choose DC reading on your multi-meter and start turning the first potentiometer with a screwdriver. Keep rotating until you see 14v reading on the multi-meter. You are done with fixing the voltage.

Now choose the second potentiometer with your screw and change the reading to current in your multi-meter. Start turning the potentiometer with the screwdriver and continue until you get 2amps rating on the multi-meter. You can set the amps up to 5amps depending on the capacity of the battery.

Check with the battery

After completing the above procedure, now it is the time to check whether the charger works or not. Connect the alligator clamps with the battery and then connect the adapter to the power source. The blue LED on the converter board will start blowing if the battery is charging. Wait for a few hours and recheck the board. The battery will be fully charged when the green LED start glowing instead of the blue.

Precaution: As the above procedure includes working closely with a high intensity of the current, they can become harmful if you make any mistake. We will suggest you wire safety kits such as the goggles, gloves, etc. while working on the procedures. Make sure that you connect the clamps properly as we mentioned. If the clamps are misconnected they can cause severe injuries and harm like as exploding the battery.  Besides, set up converter correctly and up to the only mentioned units. While starting the power source, the alligator clamps that connect the battery with the adapter may cause sparking. So, keep the kid stays away from the area and make sure no is smoking or producing fire nearby.

Both of the procedures mentioned above works finely, and they are safe. So, if you ever end up with a low car battery and don’t have access to a charge, you can use the above procedure to charge the car battery.

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