Many EV owners have experienced the same confusing moment: you plug into a fast charger next to another car, both of you start at roughly the same battery level, yet the other vehicle immediately jumps to 80–100 kW while yours sits at 30–40 kW. It can feel unfair, or even worrying—did something go wrong with your vehicle or the charger?
In reality, most charging differences are not caused by faults. They are the result of several natural factors working at the same time. Understanding these factors helps you judge whether your car is performing normally and avoids unnecessary frustration at charging stations. Let’s walk through the six reasons behind charging speed differences in a clear, practical way.
1. Every EV Has Its Own Maximum Charging Capability
This is the number one reason behind almost all charging speed differences.
Every EV model is designed with a fixed fast-charging ceiling determined by its battery chemistry, electrical architecture, and thermal management system. No matter how powerful the charger is, the vehicle will never exceed its own hardware limit.
A Nissan Leaf, for example, typically tops out around 45–50 kW. Plugging it into a 150 kW station won’t make it charge faster. Meanwhile, a Tesla Model 3 or Hyundai IONIQ 5 can briefly reach 150 kW or more under ideal conditions. When two cars charge side by side on the same charger, the huge difference often comes simply from the models themselves—not from luck or malfunction.
2. Battery Temperature Has a Huge Impact on Charging Speed
Lithium-ion batteries behave very differently at different temperatures. When the pack is too cold, the chemical reactions inside slow down, and the vehicle intentionally reduces charging power to protect the cells. This is why charging in winter often feels noticeably slower. When the pack is too hot—such as right after a long highway drive—the thermal system may need time to cool it before allowing high-power charging.
You may not see these temperature controls, but they are constantly working in the background. Different brands also use different thermal strategies, meaning two cars parked at the same charger under the same weather can still behave differently.
3. Higher State of Charge Naturally Means Slower Charging
All lithium-ion batteries share the same charging pattern: they accept the most power when the battery is low and gradually slow down as they fill up. Between roughly 10% and 50%, most EVs can maintain strong power. After 70%, the battery enters a protection phase where the system intentionally lowers the charging speed. Once you reach 85–90%, single-digit kW is completely normal.
This is not a sign of poor performance. It is simply how batteries protect themselves at high voltage. If charging feels slow only at high battery levels, your car is actually behaving exactly as designed.
4. A Charger’s Real Output Often Differs From Its Labeled Power
Many drivers assume that a 120 kW charger will always output 120 kW. In real-world conditions, this rarely happens. Charging stations can be affected by shared power distribution, grid limitations during busy hours, aging hardware, weather conditions, and even the number of vehicles charging at the same time. A station labeled “120 kW” might only deliver 60–80 kW under typical load.
This means that sometimes your car isn’t slow—the charger simply isn’t providing as much power as expected. It’s a common industry phenomenon and not a sign of vehicle problems.
5. Cross-Standard Charging Adapters Also Limit Power
As EV models from different markets appear around the world, many drivers use cross-standard adapters, such as CCS2 to CHAdeMO, CHAdeMO to NACS, or GB/T to CCS2. These adapters are not passive connectors—they contain protocol conversion chips, current-handling components, thermal structures, and safety logic. Because of this, every adapter has its own maximum supported power.
If your vehicle is capable of 70 kW but the adapter supports only 50 kW, your charging speed will not exceed 50 kW, no matter which station you use. Brands like Orientrise, Lectron, and A2Z offer different power levels depending on the model, and the performance differences can be significant. This is why confirming the adapter’s power rating is just as important as checking the vehicle’s own charging capability.
If your charging speed drops when using an adapter, it is often a normal technical limitation—not a device failure.
6. Battery Aging Gradually Reduces Fast-Charging Capability
As an EV gets older, the battery’s State of Health naturally declines. The BMS then begins protecting the aging cells by reducing the peak charging power, shortening the duration of high-power charging, and entering protective slow-charging phases sooner than before. This is a normal, expected process for all lithium-ion batteries.
If your car charges slower after several years of use, it usually reflects battery aging rather than a mechanical fault.
Conclusion: Charging Speed Differences Come From Multiple Factors, Not a Single Cause
Charging speed is shaped by the car’s design, battery temperature, charging habits, station conditions, adapter limitations, and long-term battery health. When you understand these factors, it becomes much easier to judge whether your car is performing normally.
If you want a more stable experience, the most effective approach is simple: charge when the battery is low, choose well-maintained stations, avoid extreme temperatures, and use properly rated adapters. These habits do far more to improve real-world charging performance than chasing the highest number you’ve ever seen on the screen.
The only time to be genuinely concerned is when your car still charges unusually slowly even at low battery levels, in moderate temperatures, on a strong charger, and without an adapter. Apart from that situation, most “slow charging” moments are perfectly normal.
