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Can You Start Car With Battery Charger Connected? (Automobile Safety Tips & Tricks)


Connecting a charger to your car is common when the car battery is low or dead. There are several chargers available that can charge your car battery. However, can you start car with battery charger connected?

You should not practice this method as it can cause damage to your car battery. But that depends on the situation. It’s safe to start your car if it has stored enough charge. However, never start your car while charging when there is no sufficient charge available. That might blow up the charger and harm your car battery.

So, this post will guide you on how to safely charge your car battery using a battery charger.

How Does a Car Battery Charger Work?

A charger contains its own charge, which it delivers to your car battery. The transfer of charge takes place over a long period with small charges. It’s because your car battery needs to attain a certain amperage and voltage to power the engine.


When you turn the key from ignition to “Start,” the engine gets enough electrical energy to start its mechanical processes. Moreover, one of the engine’s processes is to mechanically power the alternator.

An alternator is a component that continuously recharges the car battery while the engine is running. Moreover, it gets its energy from the engine.

Typically, an alternator provides 13.5 – 15 volts of electricity to charge your car battery. The engine easily provides enough energy so that the alternator can generate the required electric charge.

That means if your car battery is dead, you can’t start the engine. Therefore, the alternator will look for another energy source to recharge the car battery.

Since you have connected the charger to your car battery, the alternator will try to get its charge from the charger. What will happen then?

The charger might not fulfill the alternator’s energy requirement and end up blowing itself. Therefore, starting your car battery when it’s dead and connected to a charger is not recommended.

Now, there are various types of battery chargers and battery maintainers. In addition, you will find high-capacity chargers that can even boost your car’s alternator. But these high-power alternators are expensive.

So, it’s important to check the capacity of a car battery charger before buying it. On top of that, check whether it works as a maintainer.

Battery Charger vs. Battery Maintainer

You might have heard that the charging device is called a “Battery Charger” or a “Battery Maintainer.” Unfortunately, a lot of people make a mistake in considering both devices as one. That’s not the case.

A battery charger and a battery are two different devices. Both devices might look the same. These devices also share the common objective, i.e., to charge your car’s battery.

However, there’s a difference in the purposes of a battery charger and a maintainer. So let’s talk about that in detail.

Have a look at the Schumacher Battery Charger and Engine Starter for your car.

Battery Charger

You use a battery charger to charge a battery. It will use either an active wall socket or a charge storing device (like a power bank) to get current and charge the other device.

Since we are talking about a car battery, its charger works by converting energy into a charging pulse.

The charging pulse breaks off the chemical (sulfur) from the electrolytic plates inside the battery. After that, the charge in the battery is restored.

While recharging a car battery using a charger, you can set the amperage, which is the actual pulse running inside the battery. If you set more amperage than the battery’s original capacity, that might overheat the battery, eventually giving you the smell of rotten eggs. That means the battery is suffering and overcharged.

Therefore, always set the charger to at least 10 amps amperage setting, which is considered a slow charge. It’s better to slowly charge a car battery to avoid overcharging and heating. That will also extend the battery life and performance.

Moreover, you have to look for a charger that fits best for your car battery. It’s because not all chargers are perfect for all types of car batteries.

Battery Maintainer

While looking for a battery charger, you must have seen that some chargers work as a battery maintainer as well. What does that mean?

Most portable battery chargers are battery maintainers as well. They serve a different purpose. No doubt, you can use one to charge your car battery. But it’s important to know other applications of a battery maintainer as well.

A battery maintainer keeps track of the battery recharging process. As a result, it avoids overcharging and thus, improves the average life expectancy of a car battery.

A battery maintainer first analyzes how much charge is there inside the battery. Then it administers the necessary charge.

While the battery is on the recharge status, a battery maintainer will keep checking how much percentage of charge is left. The battery maintainer will go off as soon as the battery gets 100% charge.

Therefore, it will save your car battery from overcharging even if you forget to disconnect the battery maintainer from your car.

Today, you can find almost every smart car battery charger as a battery maintainer. The cost is affordable as well.

Check out the CTEK Automatic Battery Charger and Maintainer.

The Difference

The basic difference between a battery charger and a maintainer is where the device is being used.

For a common car battery, you can use a simple battery charger. It’s because you can’t leave the charger connected to your battery for a long time.

Moreover, you have to frequently charge your car battery and stay there to disconnect once the battery is fully charged. You can even unplug the charger once the battery has enough charge to power the engine.

On the other hand, go for a battery maintainer if you have a battery that you don’t frequently use. That will allow you to leave the maintainer connected to the battery even when the charging has been completed.

In addition, there won’t be any harm to the battery as the maintainer will automatically turn off.

The crux?

Every battery maintainer is a charger but not every battery charger is a maintainer.

Safety Checks While Charging Your Car Battery

If you think that your car battery is weak or almost dead, prepare the charger to recharge the battery. First, however, it’s important to perform the following safety checks before connecting the charger to your car battery.

close up of hand charging car battery
  • Make sure you thoroughly inspect your car battery for any possible cracks or corroded areas. That might lead to battery leakage, which can cause the battery to overheat and explode during recharging.
  • Check the level of distilled water in the battery. If the battery has completely dried out, don’t recharge it. That might affect the battery. First, pour some distilled water and wait till electrolytic plates get soaked into the water. Then move to the next step.
  • Clean the car battery terminals and the cables. Usually, the terminals get rusty due to humidity in the weather. This rust hinders the charging process. Therefore, clean the rust and grime from the battery terminals and the cables as well. That will ensure an efficient battery charging process.
  • Make sure you have got the right battery charger. Your car battery can only tolerate a certain amount of amperage and voltage. Beyond that, the battery will suffer from overcharge or overheating. Check out the charging requirements mentioned on your battery. You can also call the battery manufacturer and ask them what charger is suitable for your car battery. Don’t use a charger that’s not compatible with your battery.
  • While connecting the charger to your car battery, make sure you have parked your car in an open space. A good open space has ventilation. It’s because a battery gives off hydrogen and oxygen while recharging. If there’s no ventilation, these gasses can accumulate in a poorly vented area, and a small spark might cause an explosion.
  • Pull the emergency brakes while recharging your car battery. You don’t want your car rolling while connected to the charger, do you?
  • Finally, always check that your car battery really needs a recharge. If your car is not starting, it’s possible that your car battery is not dead, but there’s something wrong with the wiring. Therefore, check the internal battery connections and check if the current is properly flowing from the battery to your car.

Once your car battery is recharged, you can disconnect the charger and pack up the whole charging kit. Moreover, it’s not necessary that you fully charge your car battery. Since it’s time-consuming recharging your car battery via a charger, it’s better to let the alternator do this job.

That way, you can save time, cover the distance, and, most importantly, recharge the battery.

You have to ensure that your car’s engine gets enough power supply to start. After that, start driving your car for at least 30 minutes so that the alternator can do its job.

Final Thoughts

It’s important that your car battery has a full charge at all times. Even if you rarely use your car, it’s better to recharge the car battery first and then park your car.

Moreover, unnecessarily charging your car battery will kill its performance. Therefore, always check that your car battery really needs some juice. Only then connect a charger and recharge the car battery.

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