how to charge a car battery without a charger

How to Charge a Car Battery Without a Charger

There can be many reasons a car battery is out of juice.

There’s nothing to be worried about if you find yourself without a car charger in these situations. You can use a jump start, a power inverter, and other methods to bring the battery to life.

Let’s discuss all available ways regarding how to charge a car battery without a charger.

Safety Measures to Take Before Battery Recharging

There are some arrangements to make before unconventionally charging the car battery. These measures are essential for the safety of you and your property. Before learning how to charge a car battery without a charger, you must be aware of these hazards.

Cool Down the Battery

A car battery can overheat if it has been working extensively, under direct sunlight, or if the weather is warmer.

You must avoid charging your car batteries in these situations and wait until it cools down.

Check for Battery Leaks

A leak in the battery can lead to many troubles. Check whether the battery has any leak or smells like rotten eggs.

If you find anything, don’t proceed with charging the battery. Get away from the car and call for professional help.

Look for Signs of Corrosion

Degraded car batteries often show signs of corrosion. In this case, you may spot greenish and crusty substances around the battery ports. It generally happens with lead-acid batteries.

Stay Away from Fire Triggers

Be cautious of your surroundings before charging the battery. Make sure that there is nothing around which would cause a fire hazard.
Take protection measures, such as removing any jewelry and metal elements and wearing protective gear.

charging a car battery without a charger
Check the battery thoroughly to see if it’s faulty. Image credit: Mídia / Pexels

How to Charge a Car Battery Without a Charger

If you find yourself in a bind and need to give your dead car battery a power boost without a charger, there are a few ways to do it.

Portable Jump Starter

Portable jump starters have become extremely popular in the last decade or so. It is similar to a battery power bank that we use to charge our phones or other electronic devices. You can use it for a quick power boost so that you can drive the car to a safe place.

A portable jump starting device comes in handy when the battery runs dry and towing services are unavailable. It’s easy to use and does not take up much space in the glove box or the trunk.

Turn the ignition off and disconnect the auxiliary electronic devices, such as the air conditioning system, radio, lights, and audio devices. These things will drain the battery before it can start the engine.

There should be some distance (as far as the cords allow) between the battery and the charging device. Attach the connections and start the car by cranking it for five seconds. If the engine doesn’t kick off, wait for two to three minutes and try again.

Jump Leads

Using jump leads with a donor car is one of the common ways to charge a car’s dead battery. The device has a pair of jumper cables with metal clamps at their ends.

This process will only give enough charge to your batteries to start the engine, and the alternator takes over from there to keep charging. But a jump lead will be useless if you have a faulty battery charging system or alternator.

The donor car engine should run for at least 10 minutes before connecting the jump leads. Also, the leads should be heavy and within four gauges of length to transmit the electricity without getting melted. The jump leads should not be lengthier than six gauges.

Another Vehicle

Using a donor vehicle is another solution if you are wondering how to charge a car battery without a charger. It’s a much easier method than using jump leads. All you need to do is put your dead battery into another car for charging.

The downside of this method is that both vehicles have to have the same battery specs for compatibility. Otherwise, it will also cause damage to your battery and the donor car.

It works in older vehicles that don’t have a complicated electronic system. You have to put the dead battery in the donor car to see if it can make your battery alive.

jumpstart a car using another vehicle
You can use another vehicle to jumpstart. Photo: Michael Fawcett / Flickr

A Solar Charger

This method involves using a charger that runs on solar power. Solar energy’s power supply is endless, but this charging method is not practical. It may take around eight to nine hours to charge a battery, depending on its size and output capacity.

In other words, it’s a slow charging process and ineffective in an emergency. It’s only available until the sun is out, making it inconvenient.
To minimize the charging time, get a solar charger that matches the size of your flat battery.

UPS Power Inverter

A UPS inverter is often installed in homes as a backup power source for a short period in case of a power failure. It can charge electronic devices around the house and also a car battery.

Among many inverters, a tubular inverter battery is the most common. Besides homes, it is popularly used in RVs and campsites as backup power.

Before purchasing a UPS inverter, check the manual to ensure that your car battery is compatible with that inverter model. Thankfully, some inverters have built-in safety features that prevent overheating and overcharging.

A Battery Isolator

Another method for solving how to charge a car battery without a charger problem is using a battery isolator.

If you are a camper or RV owner, you may already know about a battery isolator. An isolator allows you to charge a battery using the alternator’s power.

The isolator sends the alternator’s power to another battery, which cannot charge the flat battery fully as it does not provide enough current.
This method is hard to apply if your car battery is dead because this is not strong like an actual battery charger. But an isolator can charge a battery just enough to start the engine.


There are a few methods of charging a car battery without a charger. Apply the one that you find the most convenient. Ensure that the battery is not faulty and there are no leaks or corrosion. Contact a professional if something seems a little off, and do not try to solve things yourself.

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