Never Connect the Negative Terminal Directly — Here’s Why

[0:00]Why can the positive terminal be connected directly when charging a car battery, but the negative one absolutely cannot? That is because the negative line has a battery monitoring unit. If you connect the charger straight to the negative terminal, the sudden surge of current at the moment of power on can easily damage that unit. Once that happens, the start stop system will stop working and the alternator will think the battery is always low on power. It will keep charging nonstop which leads to overcharging and a much shorter battery life. That is why in the factory, the negative terminal is always connected to the metal body of the engine instead. Also, the positive and negative terminals must never be reversed or the car's computer board could get damaged.