How to Charge a Car Battery Without a Charger?

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When you drive a car, there are certain scenarios that you always hope will never happen to you. For example, we hope our brakes never give out when we’re on the freeway, and we hope we don’t break down in the middle of anywhere with no wat to contact help.

Another common nightmare scenario is suddenly discovering that our battery is either very low on power or completely dead and therefore unable to start up the car. If it happens when you’re at home and you have a charger handy, then you can charge the battery without any problem. But what if you don’t have access to a charger? How to charge a car battery without a charger is a very tricky problem. This kind of emergency situation calls for knowledge on three possible solutions:

1) A charger-free trickle charge

2) Using an Inverter

3) A jump-start

We will explain the procedure for both of these methods below, but before considering either one, you should ensure you have safety goggles and strong gloves that you can wear for the duration — safety first! Please also note that for this example, we are talking about lead acid car batteries.

1. How to Charge a Car Battery Without a Charger –Trickle Charge

For this first method, you’ll also need to prepare some wire probes with clips and a 12V light-bulb (around 21W). If you have Christmas lights handy, they might work as well. On top of that, you need a steady power supply to use in place of the charger. Your power supply needs to plug into your home outlet, and will then supply an appropriate power level to safely charge the battery. Your home outlet is a far greater voltage than the car battery, which is why you can’t connect it directly.

Step 1: Confirm your power supply

What can you use as a power supply? A bench power supply unit is ideal because it has variable settings so you can match your needs for the car battery. If you don’t have any kind of power supply unit apparently handy, you can use something more every day like your laptop charger. For this example, we’ll describe it using a typical bench power supply unit that many might have at home.

When setting up your power supply, we advise you to keep the power supply and battery as much distance away from each other as you can.

Step 2: Position the bulb/holiday lights between the power supply and battery

Hook up the lights to the power supply so that when you start the charging process, the lights will come on to confirm that there is a
current flowing between the supply and battery. Without the lights, you might wait for hours wondering if it’s working but with no luck. The bulb/lights have an additional function here, which is to draw the bulk of the current so that you can maintain a safe trickle into your car battery. This helps prevent overcharge damage.

Step 3: Hook up the power clips

Connect one of the black negative clips to the power supply and the other to the car battery. Then do the same for the positive clips. Once the clips have made contact, the power should start flowing immediately.

Step 4: Keep Watch

For safety reasons, you should remain with your car while the charging process is taking place. Observe if anything is overheating,
smoking, sparking or showing some other sign of a problem. If anything looks amiss, shut off the power and seek help.

After about 20-30 minutes, remove the negative clip followed by the positive clip and then check the car’s battery’s voltage with a multimeter. Your goal here is just to have some charge, enough to start the engine. If you can start the engine, then you’ll be able to charge it more as you drive or run the engine.

2. How to Charge a Car Battery Without a Charger – Home Inverter

The following method is a very fast method of charging that can fully restore the battery within 3 hours. This method uses DC, however, and is, therefore, less controlled than a trickle charge. It should be used very sparingly:

Step 1: Set Up the Connections

Take the inverter you have and set up the connections. Do not plug in at this point. Hook up the black negative clip to the appropriate battery port, and then the red positive clip.

Step 2: Plug in the Inverter

Once you’ve checked the connections, plug in the converter to your home power outlet.

Step 3: Wait for Charge

It should be able to charge the battery fully inside of 3 hours, but it’s not as controlled as a trickle, and overcharge can do some
damage to the battery components. Use with care!

3. How to Charge a Car Battery Without a Charger –Jump-Start

This method is well known in itself, but most would not claim to know how to do it. You’ll need a second car to perform this, so either use another family car or that of a neighbor or willing citizen who is nearby and ready to assist. You’ll also need proper jumper cables in your car.

Put simply, this is how you perform the jump start:

Step 1: Ensure the two cars are close together but not touching

Park the assisting car close to yours, but make sure they are not making any kind of contact. Ensure both cars are powered completely off and sitting idle.

Step 2: Open the hoods

Pop the hoods on both vehicles and confirm the location of the battery in each. Ensure you can tell clearly which connector is positive and which is negative.

Step 3: Hook up the clamps

Start with the positive (red) cable clamp and attach it first to the positive connector of the dead battery, and then onto the positive
connector of the good battery. Next, attach the negative (black) cable clamp to the working battery. Finally, attach the final negative clamp to any unpainted metal surface of the car with the dead battery.

Step 4: Starting engines and removing cables

First, start the good engine with the working battery. Then start up the dead car. After that detach cables in reverse order:

Negative clamp from metal surface in a dead car
Negative clamp from good battery
Positive connector from good battery
Positive connector from dead battery

Finally, just let the engine run for up to 15 minutes to build up some charge.