When you spend a fortune on a smartphone boasting an 8000mAh large battery, you might think you can finally say goodbye to battery anxiety. However, after a few days of use, you realize the battery life is just so-so; out of the 8000mAh battery, the actual usable capacity might only be around 7000mAh.
01. Battery Capacity Locking in Most Smartphones
On July 26, 2026, Geekerwan, a well-known digital content creator on Bilibili, released a comprehensive smartphone battery life review video, which quickly climbed to the top of the site's rankings. The team self-funded the purchase of 78 retail smartphones on the market, covering mainstream brands such as Apple, Huawei, Xiaomi, OPPO, vivo, Honor, and Samsung. The testing methodology was quite hardcore. Instead of relying on system-reported data, they directly disassembled the batteries and, in accordance with the 0.2C discharge rate method specified in the national standard GB/T 18287-2013, used professional equipment to measure the actual cell capacity truly available to users from a full charge to automatic shutdown. The test results were striking.
For most models participating in the test, the battery capacity release rate (measured usable capacity divided by the nominal capacity) generally ranged between 87% and 95%. There were also significant differences in performance among different brands. Some models had a measured release rate close to the nominal value, with almost no capacity locking; while others showed obvious capacity shrinkage, with some models even having a release rate below 90%. The model with the most severe capacity locking, boasting a nominal 10000mAh battery, had an actual usable capacity of only about 8568mAh, resulting in a release rate of less than 88%. Why does this discrepancy occur? This is not a battery quality issue, but rather manufacturers artificially limiting the usable capacity at the system level. The professional term for this is capacity locking.
02. Why Does Capacity Locking Occur?
Li Xiaolong李小龙, CTO of Huawei's Terminal BG, explained this mechanism using the analogy of pouring water from a cup. The nominal battery capacity refers to the total amount of electricity released when discharged to the cutoff voltage (typically 2.8V or 2.5V according to national standards); whereas a smartphone has a shutdown voltage during actual operation, which is like a valve at the bottom of the cup. If the shutdown voltage is higher than the cutoff voltage, the water at the bottom of the cup cannot be poured out.
Over the past few decades, smartphone components have been designed based on the characteristics of traditional graphite batteries. Graphite batteries have virtually no power to discharge below 3V, so setting the shutdown voltage above 3V was completely reasonable. However, in the last two years, high-silicon anode batteries have been rapidly popularized, and they can still release a significant amount of capacity even in low voltage ranges like 2.8V. If core components such as the PMIC (Power Management IC) in the smartphone have not been adapted for low voltage and still force a shutdown above 3V, the power at the bottom of the silicon anode battery is wasted in vain.
Geekerwan also pointed out that, out of consideration for protecting battery cycle life, manufacturers reserve buffer spaces at both the upper limit of charging and the lower limit of shutdown. This is not an issue with a single manufacturer, but rather a lack of a unified parameter expression standard in the industry. Is the labeled battery capacity the rated capacity, typical capacity, or actual usable capacity? Is the labeled fast charging power the peak power or average power? Next time you see an advertisement for an 8000mAh ultra-large battery, you might as well ask one more question: according to what standard is this capacity labeled?
#SmartphoneBattery #SmartphoneBatteryCapacityLocking