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Can You Start a Car with a Battery Charger Connected?

Can You Start a Car with a Battery Charger Connected?

Dealing with car issues can be troublesome, and it’s not uncommon that a simple mistake can cause damage to your automobile. 

You must take certain provisions when repairing or maintaining your car personally, and battery issues are one of them. 

So, can you start a car with a battery charger connected?

You should not start a car with a battery charger connected if the battery is dead because the battery charger doesn’t have enough current to start the car. If the battery is sufficiently charged, then it shouldn’t be an issue. But there are several other factors to consider before risking your vehicle’s battery.

Starting a car with a battery charger connected can be dangerous in some cases, and we’ll go over them one by one. 

So, make sure to read this article to the end so you know what to do when dealing with battery chargers, and the best way to start your car. So, keep on reading!

What is a battery charger, and how does it work?

A battery charger, much like a cellphone charger, is a device designed to revive dead batteries

The charger is either plugged into an electrical socket or uses a portable energy storage system to deliver charge to a drained battery

There are different types of battery chargers for different types of batteries, based on their voltage ratings and battery capacity, so you’ll have to make sure that you get the right one for your car battery.

Starting a car with a battery charger connected

When you’re dealing with charging your battery and starting the car, you need to take care of some very important things.

Starting your car when the battery is charged and the battery charger is connected as well isn’t that much of an issue, and you can start the car easily. 

This is because the voltage required to turn the alternator on will be taken from the fully charged battery, and not the battery charger.

However, if the battery has insufficient charge, and you try to start the car with the battery charger connected, this can be very harmful. This is because the car will try to take the required voltage from the battery charger, which is not usually designed to sustain that level energy boost. 

Starting a car on a dead battery with a charger connected can cause the fuse on the battery charger to blow out or burn the charger itself.

Heavy-duty battery chargers with jumpstart capability are more viable in the case you want to start your car right away. 

These battery chargers are designed with a 12 V adapter, compared to smaller battery chargers which have around a 4 V adapter. 

Should I use an older charger or invest in a new smart charger?

If you’re trying to save a few bucks by using an old charger, you might cause more harm to your battery. 

Older battery chargers are designed to keep on charging your battery even after it’s been fully charged, whereas newer chargers have a built-in cutoff system that stops them from charging once the battery is fully charged.

What kind of charger is best for me?

If you’re looking to get a charger for your car, there are several things that you need to consider in order to get the best charger.


The size of the car’s engine will affect the type of charger you need. Bigger engines require bigger batteries, which in turn require bigger battery chargers.

Battery types

The type of charger you need depends on the type of battery you have. 

Traditional lead-acid batteries require standard chargers, which are generally cheaper, with simple interfaces and a regular number of features. 

However, these are not suitable for AGM/EFB batteries or cars with a start/stop function.

Smart chargers are generally much more advanced and capable of different charging modes depending on the battery’s charge level. 

These can also help improve the battery’s lifespan by switching from regular to trickling charge when the battery is at full capacity.

You can also use some models of newer smart chargers to charge other devices, like a laptop or mobile phone. 

There are different types of chargers, and you can browse through them to find the one that suits your needs the most. 

This helpful article I have attached has several different portable battery chargers listed, so you can check it out by clicking on the link here.

Trickle chargers vs Regular Chargers

It is also important to understand the difference between regular chargers and trickle chargers when dealing with your car battery.

Regular chargers are designed to charge your car battery and will keep charging the battery regardless of the battery’s current level of charge. 

Therefore, you need to make sure that once the battery is fully charged, you should disconnect the charger in order to avoid overcharging and damaging the battery.

On the other hand, trickle chargers deliver low amounts of voltage to charge a battery over a long period of time slowly. 

This is best for when you’re storing your battery away for an extended period without the worry of the battery overcharging.

However, trickle chargers are not to be confused with maintenance chargers designed to shut off once the battery has reached the set amount of charge level.

Regular chargers are best for when you require a quick charge, whereas trickle chargers are ideal for when you are storing the battery away.


When dealing with a battery charger and a dead battery, it is advised to make sure that the battery is charged to a certain level before you try to start the car, if you’re using a regular small charger for the battery.

If you’re using a regular charger, connect it to the battery and let the vehicle charge, then remove the charger before starting the car, just to be safe.

Heavy-duty chargers are better for when you want to jump-start the car from the battery charger as well and can withstand the voltage required to start the car.

That’s it for this article. I hope you understand the different battery chargers types and whether you can start a car with the battery charger connected. Good luck!

Zach Reed

Hi, I'm the founder of! Having owned a wide variety of vehicles in my life, I was astounded at how hard it can be to find answers to common automotive questions. Rather than sit idly, I decided to create this website to help others!