Recently, we've received many private messages from fans complaining: "My electric car can run 500 kilometers when fully charged at home, but only 400 kilometers when fully charged at a public fast charger. Did the charger manufacturer secretly adjust the power?" "Last time I charged my car to 100% at a fast charger, but it ran out of power after less than half the distance. Is this charger falsely labeled?"
Such doubts are growing, and some bloggers even claimed that "charger manufacturers can adjust charging coefficients to make car owners think the battery is fully charged when it's actually only 70-80% full." Overnight, "charger power adjustment" has become a sensitive topic among car owners, with many suspecting that all chargers around them are "rigged."
As car owners, should we really worry about chargers being "tampered with"? Is power adjustment a necessary technical measure or an underhanded trick? Why do we always feel that chargers are delivering "fake power"? In this article, we'll start from technical principles to break down the underlying logic of charger power adjustment, fully analyze the real reasons for "not being able to fully charge," and help you avoid the pitfalls of charging.
PART 01
⚙️ Technical Principles of Chargers: From AC to DC, the Underlying Logic of Power Adjustment
To understand the truth about power adjustment, we first need to clarify the different power adjustment logics of different types of chargers. Currently, electric vehicle chargers on the market are mainly divided into two categories: AC slow chargers and DC fast chargers, with vastly different underlying logics for power adjustment.
1. AC Chargers: Stable Slow Chargers That "Only Supply Power, Not Charge"
AC chargers, commonly known as "home chargers," are the daily choice for most car owners. According to industry standards, the rated output power of ordinary home AC chargers is around 7kW, and many car owners actually use them at around 6kW, such as owners of Gaoshan electric vehicles whose home chargers stabilize at 6kW.
The core feature of AC chargers is that they only provide power output and do not directly participate in battery charging: they transmit alternating current from the grid to the vehicle's on-board charger, which converts the alternating current to direct current before inputting it into the power battery. This means that the actual charging power of an AC charger is not determined by the charger itself, but by the power limit of the on-board charger.
For example, if your vehicle's on-board charger has a maximum power of 3.3kW, even if you connect it to a 7kW AC charger, the actual charging power will only reach 3.3kW. Many car owners complain that "AC chargers charge slowly," but the essence is not the charger's problem, but the limitation of the vehicle's hardware.
The power adjustment of AC chargers is mostly for the safety of grid load. Old communities have limited transformer capacity, and if multiple AC chargers charge at full power simultaneously, it can easily cause the transformer to overload and trip. In such cases, the community's intelligent power allocation system for chargers will automatically intervene, dynamically adjusting the charging power of each charger to distribute electricity during off-peak hours and avoid failures during peak electricity usage (for example, some communities reduce charging power from 7kW to 3.5kW during evening peak hours and restore full power in the early morning). This kind of adjustment is a mandatory requirement by the power department, fully compliant, and has nothing to do with "underhanded tricks."
2. DC Chargers: Step-Down Power Adjustment Is to Protect the Battery
DC chargers are the first choice for emergency energy replenishment during long-distance trips, commonly known as "fast chargers." DC chargers directly output direct current to charge the power battery, without the need for conversion by the on-board charger, so the charging power is higher. Mainstream fast chargers have a power of 60kW-120kW, and Tesla's V3 Supercharger even has a peak power of 250kW.
However, many car owners find that the fast charging power is not constant: when charging at a State Grid fast charger, the power of Gaoshan electric vehicles basically fluctuates around 60kW, drops to 30kW when charged to over 90%, and directly drops to around 6kW when charged to 96%, which is the same as the charging power of home chargers; the 250kW peak power of Tesla's V3 Supercharger can only last about 3 minutes, then steadily decreases, and when the battery reaches 55%, the power is similar to that of the V2 Supercharger.
Many car owners think this is the charger "secretly reducing power," but in fact, it is a necessary design for the collaboration between the Battery Management System (BMS, the "brain" of the battery) and the charger. The charging process of the power battery is divided into three core stages:
Pre-charging stage: When the battery level is below 20%, the cell activity is low, and the BMS will control the charger to charge at low power to avoid damage to the internal structure of the cell caused by high current impact;
Constant current fast charging stage: When the battery level is between 20%-80%, it is in the optimal charging range, with low internal resistance and low heat generation. At this time, the charger outputs at full power to maximize energy replenishment efficiency;
Constant voltage trickle charging stage: When the battery level exceeds 80%, the cell voltage gradually approaches the saturation value. Continuing to charge with high current will cause the cell to heat up and lithium plating, seriously shortening the battery life. At this time, the BMS will instruct the charger to gradually reduce the charging power, maintain the voltage near the saturation value, and slowly fill the remaining power.
This step-by-step power adjustment is a universal technical standard followed by global car manufacturers and charger manufacturers, with the core purpose of balancing energy replenishment efficiency and battery life, and has nothing to do with "underhanded tricks."
