Understanding EV Battery Discharge: Principles and Precautions

Electric vehicles are now a common sight in daily life, bringing convenience to people in cities and rural areas alike. However, not everyone fully understands how EV batteries charge and discharge. Today, let us explore the discharge process of electric vehicle batteries and the important points you should not overlook.

Many people are already familiar with the charging process. Charging is like an energy transformation journey: by inputting electrical energy, the lead in the battery liquid is gradually reduced back to metallic lead, storing the energy for later use. What about discharge, then? Using reverse thinking, it is easy to understand. During discharge, metallic lead and the electrolyte undergo a chemical reaction: the metallic lead becomes lead ions while releasing valuable electrical energy. From this charge-discharge principle, it is clear that the process works like a simple reversible chemical reaction - it may look complex, but it follows a clear internal logic.

However, during the discharge process, there are several precautions that work like hidden rules and deserve special attention.

First, if the battery is completely drained and you insist on continuing to discharge, it is a disaster for the battery. This behavior is like a ruthless destroyer: it gradually dissolves the battery plates. In severe cases, the plates may shed and internal short circuits may occur, leaving the battery unable to charge or discharge, like a lifeless shell.

Second, because an EV draws a large current while riding, when the battery is nearly empty the power will noticeably drop, like a deflated ball. At this point, if you can clearly feel the decline in power, you should promptly switch off the power and switch to pedal-assist riding, heading to a power source for a timely and sufficient charge. In this way, you can generally avoid deep over-discharge and keep the battery in good condition within a reasonable range of use.

Third, you may have noticed that when the battery is about to run out, stopping the bike and letting it rest for a while seems to recover some charge. However, if you frequently rely on this seemingly unexpected power to keep riding, that is a serious mistake. This behavior overdraws the battery's potential and easily leads to over-discharge, causing serious damage to battery health.

The consequences of over-discharge should not be underestimated. Once a battery has experienced over-discharge, its capacity gradually declines, like a sponge that has shrunk. Worse still, no matter how long you charge it afterward, the battery can hardly return to its original capacity. At this point, many people mistakenly believe the battery is not fully charged and charge it excessively, only to fall into the overcharging trap. In this vicious cycle, the capacity keeps shrinking until the battery ends up being scrapped.

There is also a practical way to judge over-discharge: use the speedometer. Generally, bikes that have not had the speed limiter wire removed reach a maximum speed of about 20 km/h. When the battery is nearly depleted, the maximum speed may suddenly drop to 11 km/h. When you notice this obvious change in speed, to keep your battery healthy and long-lived, it is best to switch to pedaling.

In short, understanding how an EV battery discharges is essential. It determines how well you can care for the battery and how long it will last. By strictly following the discharge precautions in daily use, you can keep the battery in top condition through every charge-discharge cycle and enjoy reliable power for your journeys. Master these principles, use them correctly, and your electric vehicle will remain a dependable and long-lasting companion, whether you are riding through busy city streets or quiet country roads. Share these insights with others so that more people can understand battery care and contribute to greener, more convenient travel.