Battery Condition Comparison Based on Tesla Charging Habits

The two charging graphs presented here are real data provided by a Korean user and a Chinese user who contacted us through the ‘Contact via Email’ feature in the Dr.EV app to inquire about their battery condition. All personal information has been removed, and only the necessary data has been used.

First User (Left Graph)

The user on the left performs almost all charging using DC fast charging.They frequently charge to 100 percent, and their daily charging routine also depends almost entirely on fast chargers, with almost no use of slow AC charging.

Second User (Right Graph)

The user on the right performs nearly all charging using slow AC charging and typically charges only up to 80 percent or less. Fast charging is used only in exceptional situations, and their battery is normally managed through consistent AC charging.

Since their charging habits differ so drastically, the actual battery graphs of these two vehicles show substantial differences as well.

Comparison of Cell Voltage Graphs

Left User: As shown in the left graph, the cell-voltage lines spread farther apart as charging progresses. In the later stages of charging (the high-voltage region), the difference between cells becomes even more pronounced. This occurs because repeated fast charging and frequent 100-percent charging cause the weakest cell to degrade faster, leading to charging behavior that differs from the other cells. 

This difference appears directly in the voltage patterns: the spacing between the lines widens, and the imbalance becomes clearer toward the end of charging.

Right User: In the right graph, the cell-voltage lines rise almost perfectly aligned with each other. This indicates that the cells are aging at similar rates and do not show noticeable differences in their charging behavior. In other words, the likelihood of a weak cell breaking down early is low, and the entire pack maintains a uniform condition.

Comparison of Cell Voltage Deviation

Left User: The voltage deviation fluctuates significantly throughout charging, and increases sharply near the end. This happens because the more degraded cell reacts differently in terms of charging speed and voltage response. This represents a classic pattern where one weak cell drags down the overall pack balance.

Right User: The voltage deviation remains low and stable throughout the entire charging session.This means the cells are aging at similar speeds and behave consistently during charging.

Although both users have the same Tesla battery pack, the difference in charging habits alone leads to dramatically different rates of cell aging and overall cell balance.

Fast-Charging User + Frequent 100% Charging

• The weakest cell ages first

• Cell differences widen significantly over time

• Voltage lines spread widely during charging

• Voltage deviation is high and spikes sharply near the end

Slow-Charging User + Frequent 80% Charging

• Cells age at similar rates

• Differences between cells remain minimal

• Voltage graph stays consistent and uniform

• Voltage deviation stays low and stable

This case aligns well with established theory showing that charging habits directly influence the rate of cell aging and the balance state of the battery pack.