Provided your car’s battery is in an easy-to-reach location such as the engine bay or the trunk, removing it is a fairly painless process. “Disconnect the negative terminal first and then disconnect the positive terminal,” Hines tells us. The reason it should be done in that order, he says, is to mitigate the risk of electrocuting yourself.
As we already said, you should always disconnect the battery when changing a headlight bulb. It’s very important to disconnect the battery when performing any electrical work on your vehicle. You could end up causing serious damage to your car if you’re not careful. You don’t need to remove the battery.
The safest approach is to disconnect the ground wire of the battery. Many car owners wonder about their vehicle’s electrical system and are scared to touch anything for fear of damaging the circuits. While most car batteries have enough amperage to do severe damage to you, the voltage of 12V is not enough to cause any harm.
The alternator will recharge the battery while it pulls power from the battery. You need to open the hood and remove the battery. The battery connects to the headlights, so if you disconnect the battery, you only need to remove one nut (sometimes two). You will then see three wires connected to a harness — usually plastic or rubber.
Loosen the nut and remove the cable from the battery post. Position the cable so that the end is touching no part of the car body. You have never taken away the power supply to the central computer, although some electricity is still stored in the car's capacitor. Drain the remaining electricity from the battery.
A popular method of resetting the check engine light, although not necessarily recommended, is to disconnect the car battery to remove the power source to the car's central computer. If your check engine light comes on in your car, the first thing to come to mind is whether there is a repair needed or if the light was triggered by a faulty result.