Can You Use A 12V Battery While Charging It?

We may often find ourselves in a situation where we have to charge a car battery but also need to use the battery for some kind of device. You may be thinking it may overheat or cause any trouble. But will it really damage the battery if you use it while charging?

Well, if you have a smart charger, using 12v battery while charging will not cause any problem. But it is safer to not use any electronic devices while you charge because it may accidentally damage them. 

Let’s go through the details below.

Can You Use A 12V Battery While Charging It?

The direct answer is yes you can! The first step is to consult the car’s owner’s handbook. While linked, every smart battery charger on the market may securely charge your 12V automobile battery.

The manufacturer may not advise recharging the battery while connected in some exceptional cases. This is to safeguard sensitive electronic devices from being destroyed if the incorrect charger is used.

Older chargers can deliver extremely high charging electric current, which might harm electrical components.

Nowadays trickle chargers simply charge at a low current, which is quite safe.

The alternator, which provides a modest current, is meant to charge your automobile battery.

Another issue with charging too rapidly is that the acid inside the battery might boil. This might push battery acid out from the vent or, in the worst-case scenario, split the battery casing.

Battery acid is extremely caustic and may readily harm anything it comes into contact with.

Is It Bad to Use a Battery While Charging?

If you take a few measures, charging a car battery even while connected is perfectly safe. The alternator charges up the battery while the automobile is operating, thus it’s built to charge when attached to a vehicle.

Although the battery is not at risk of harm, the possibility of shocks and sparks increases since the battery is working in the car.

You can ensure that you’re charging your battery securely by following a few simple steps:

  • First and foremost, when charging a battery that is still attached to a car, it is recommended that you use protective clothing, such as gloves and eye protection.
  • You also need to pay attention to the voltage of the charger. At no point throughout the charging procedure, apply a power supply that surpasses 14.7 volts. The excellent news is that any automobile trickle charger, jump starter, or battery manager will fall short of this standard. The safest way for this is to use smart battery chargers.
  • Lastly, ensure you’re following all other charging-related safety precautions. This means charging in a well-ventilated place and avoiding direct sunlight, which can overheat the battery, therefore, speeding up the charging process. 

Before charging, ensure the battery is free of cracks or acid leaks. If you notice anything, instead of charging the battery, you must replace it.

How To Charge A Car Battery While Still Connected?

If you want to charge a car battery even though you are using it, you should follow some steps to avoid any problems.

Step 1: 

Make sure the car is switched off and the keys aren’t in the ignition. While charging a battery that is still attached, this is very crucial.

Connecting the charger’s clamps while the car is running might result in major problems, including shocks and other accidents.

Step 2: 

Remove the hood and figure out how you’re going to attach the clamps.

Follow the owner’s manual for appropriately installing the O-ring connections if you’re using these for a fixed tender installation. 

If you’re going to utilize alligator clamps, make sure that there is a sufficient terminal exposed to properly connect the clamp.

In certain cases, the only way to get to the battery terminals is to remove the connections. Even if that’s the situation, the engine’s battery can be left while it is charged.

Step 3: 

Check if the battery charger is adjusted to the proper voltage and that it has been switched off and disconnected before connecting it.

Step 4: 

Connect the positive terminal to the positive clamp. This is often red and denoted by a plus symbol (+). Then, connect the negative clamp towards the black negative terminal indicated with a minus sign (-).

Step 5: 

Start charging the battery by turning on the charger.

Step 6: 

Whenever the charge is complete, switch the charger off or disconnect it, then release the clamps in reverse orientation (black first, then red).

When you’re using a fixed trickle charger or battery maintainer, then you may leave it on all the time if necessary.

Can A Car Battery Charger Be Left on Overnight?

It’s okay to keep your vehicle battery charger on 24/7 provided you’re using a smart charger that will default to float mode, maintenance mode, or switch itself off after the battery is completely charged.

If you use a charger lacking a microprocessor all night, you will risk overcharging the battery.

Is It Possible to Start My Car When The Battery Charger Is Connected?

This is dependent on the circumstances, but the basic line is that it is not a good idea.

For a conventional automobile battery charger, chargers are only intended to give a relatively low current, perhaps 10 amps maximum.

If you try to run your automobile, the battery may provide 100 amps or more.

Attempting to pull 100 amps from your charger will almost certainly break a fuse and maybe damage it.

The main exception is when the battery is sufficiently charged to provide the requisite current.

Is It Safe To Plug In A Car Battery Charger?

If you drive frequently, it’s safe to keep your phone’s vehicle charger plugged in when you’re not using it.

The charger’s energy consumption is insignificant in comparison to the battery’s entire capacity.

To avoid parasitic discharge, unplug the car’s battery while not driving for a prolonged length of time.

And sometimes, in some cases, you should remove the battery from the car before charging.

In What Circumstances Should You Disconnect the Battery From The Vehicle Before Charging?

If you have an older charger:

The charging current is limited by a microcontroller in modern chargers. Older chargers may deliver an excessive amount of electricity, causing harm to the vehicle’s electronic systems.

If Your Battery is Completely Depleted:

A trickle charger will not be capable of charging it in this instance. This is because the modest current flow of the trickle charger is inadequate to surpass its internal resistance.

You will need a current maintenance-style charger that can restore batteries for this. These, on the other hand, employ stronger currents and pulse currents, which may cause harm.

As a result, you may not use them with a car battery attached.

When you Charge a Depleted Lead-Acid Battery:

Although most automotive batteries are now closed for life, previous models released hydrogen gas, which is very explosive.

Charging those batteries while within the engine compartment might result in an explosion.


If you need to charge a battery, always be cautious and stay safe from any kind of trouble by following safety measures.

Your car battery may not cause any issue even when you use other devices using the battery power, because of the smart charging system.

But if you do not have one, then it is advised that you should not use any equipment powered by the car battery. 

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