Will the electric car automatically cut off power when fully charged?
3 Answers
Electric cars do not automatically disconnect when fully charged, but the charging device has protective settings that automatically cut off the main charging device after full charge and enter a float charging state. That is, a small current is used to continue charging the battery, which is then called float charging, also known as trickle charging. The purpose of float charging has three aspects: Extend lifespan: Maintain the battery voltage within the float charging voltage range, where the corrosion of the battery's grid (the conductive skeleton of the electrode plate) is at its slowest, thus extending the battery's lifespan. Compensate for self-discharge loss: Replenish the capacity loss caused by the battery's self-discharge to keep the power sufficient. Inhibit sulfation: Suppress the sulfation caused by the recrystallization of active materials.
Modern electric vehicles can indeed automatically cut off power when fully charged, thanks to the intelligent control of the Battery Management System (BMS). When the charging station starts supplying power, the BMS continuously monitors the battery voltage and temperature. Once the charge reaches the set threshold (e.g., 100% or the user-defined charging limit), the BMS sends a signal to the charging station to cut off the current. I've studied the charging logic of several mainstream models, which also incorporate additional buffer zones. For instance, charging speed slows down when the battery reaches 98%, followed by a trickle charge in the final stage to protect the battery. Once fully charged, even the charging gun lock is automatically released. While the technology is highly reliable, it's advisable not to frequently drain the battery completely before recharging. Lithium-ion batteries are most durable when cycled within the 20%-80% range.
After five years of commuting with an electric vehicle, I can definitively tell you that charging absolutely stops automatically! Last week, I intentionally tested it by charging my car to 100% using a home charging station. The mobile app immediately popped up a 'Charging Complete' notification, and the charging station's indicator light switched from blue to solid green, ceasing to flash. Automakers are highly cautious about battery overcharging risks, hence they've implemented dual safeguards: the vehicle's onboard controller monitors the battery level, while the charging station itself has an independent detection module. The only thing to note is the logic differences between brands. For instance, Tesla allows setting a charging limit (recommended at 90% to prolong battery life), whereas most domestic brands enforce cutoff above 95%. If you're in an older residential area with unstable line voltage, installing an overcharge protector is advisable for added peace of mind.
