Many replacement batteries sold on online marketplaces advertise impressive performance specifications. High capacity ratings, in particular, are often used to make products appear more attractive to potential buyers. But does the printed capacity actually reflect the usable energy available in real-world operation?
This question was the focus of our detailed four-part test series. We examined a lithium-ion replacement battery sold through AliExpress and advertised with a capacity of 3,600mAh.
The investigation focused on analyzing the installed battery cells, measuring cell voltage and internal resistance, and determining the actual usable capacity under reproducible test conditions.
Complete Video Test Series
For full technical documentation, the entire testing process was recorded across four videos.
Playlist Overview
Full Playlist:
Battery Test Series: Does the AliExpress 3600mAh Battery Deliver Its Claimed Capacity?
Battery Test Series: Does the AliExpress 3600mAh Battery Deliver Its Claimed Capacity?
Part 1
- Opening the battery pack
- Visual inspection of the cells
- Initial assessment of the advertised capacity
Part 2
- Analysis of the installed cells
- Measurement of individual cell voltages
- Internal resistance testing
- Examination of the Battery Management System (BMS)
Part 3
- Capacity testing using the Heltec HT-CC40ABP
- Five complete charge and discharge cycles
Part 4
- Evaluation of test results
- Comparison between advertised specifications and actual performance
The complete playlist provides a transparent and comprehensive look at the professional evaluation of a replacement battery and documents all measurements and findings.
Analysis of the Installed Battery Cells
After opening the battery pack, the lithium-ion cells were inspected and analyzed.
A search for manufacturer information and technical datasheets did not produce any conclusive results. As a result, the origin and actual specifications of the cells could not be reliably verified.
Measured Values
| Measurement | Result |
|---|---|
| Cell Voltage | 3.90 V |
| Internal Resistance per Cell | 23 mΩ |
| Battery Pack Voltage | 19.60 V |
| Internal Resistance after BMS | 96.04 mΩ |
No significant irregularities were observed among the cells. The voltages were nearly identical, and the measured internal resistances were also very similar.
However, these measurements alone do not reveal the actual usable capacity of the battery pack.
Capacity Measurement Using the Heltec HT-CC40ABP
To determine the actual usable capacity, the battery was tested using a Heltec HT-CC40ABP Battery Capacity Tester.
This professional testing system supports automated charge and discharge cycles and provides highly reproducible results.
Testing Procedure
The battery underwent a total of five complete charge and discharge cycles.
Discharge Phase
- Discharge voltage: 12.5V
- Discharge current: 2A
Rest Phase
- 15-minute stabilization period
Charge Phase
- Charge voltage: 21V
- Charge current: 2A
Second Rest Phase
- Additional 15-minute stabilization period
The entire process was then automatically repeated for multiple cycles.
Capacity Test Results
The very first discharge cycle already revealed a significant discrepancy compared to the advertised specification.
Measured Capacity Values
| Cycle | Result |
|---|---|
| First Discharge | 1.60 Ah |
| First Charge | 2.326 Ah |
| Second Discharge | 2.292 Ah |
| Second Charge | 2.334 Ah |
| Third Discharge | 2.294 Ah |
| Third Charge | 2.290 Ah |
| Fourth Discharge | 2.305 Ah |
| Fourth Charge | 2.293 Ah |
After several cycles, the usable capacity stabilized at approximately:
2.3Ah or 2,300mAh
Comparison: Advertised Capacity vs. Reality
The seller advertises the battery as having:
3,600mAh
However, the actual measured capacity was only:
Approximately 2,300mAh
Difference
- Advertised Capacity: 3,600mAh
- Measured Capacity: 2,300mAh
- Difference: 1,300mAh
This represents a deviation of approximately:
36%
Why Are Capacity Tests So Important?
Many buyers focus exclusively on the advertised battery capacity when making a purchasing decision.
In reality, what matters most is the amount of usable energy the battery can actually store and deliver.
Professional capacity testing helps to:
- Determine actual battery performance
- Identify quality differences between products
- Detect battery aging and degradation
- Support informed purchasing decisions
- Evaluate repair possibilities
- Assess whether cell replacement is economically viable
What Can High-Quality 18650 Cells Achieve?
Modern premium-quality 18650 lithium-ion cells commonly achieve capacities of 2,500mAh or more, depending on the model.
Well-known high-performance cells can reach approximately 3,000mAh per cell while maintaining excellent power delivery capabilities.
Available examples can be found here:
The tested replacement battery did not achieve performance levels comparable to these high-quality cells.
Sustainability Through Battery Repair and Cell Replacement
Not every battery with reduced performance needs to be replaced entirely.
In many cases, professional cell replacement can be a practical solution.
Benefits
- Conservation of resources
- Reduction of electronic waste
- Reuse of existing battery housings
- Extended device service life
- Improved performance through modern high-quality cells
Whether a repair is technically practical should always be assessed individually.
Where Are These Types of Tests Useful?
Capacity testing and battery diagnostics are especially valuable for:
- E-bike batteries
- Power tool batteries
- Garden equipment batteries
- Industrial battery packs
- Medical technology batteries
- Robotic systems
- Lithium-ion battery packs
- Custom battery solutions
Professional Consulting by AkkuPlus
AkkuPlus supports private customers, commercial users, repair workshops, and industrial clients with:
- Battery repairs
- Cell replacement services
- Capacity testing
- Battery diagnostics
- Replacement batteries
- Chargers and accessories
- Custom battery solutions
Conclusion
The tested AliExpress replacement battery failed to achieve its advertised capacity of 3,600mAh during practical testing.
After five charge and discharge cycles, the actual usable capacity stabilized at only about 2,300mAh.
This test clearly demonstrates why independent technical evaluations and professional capacity measurements are essential. Anyone seeking to assess the real performance of a battery should rely on objective measurements rather than marketing claims or printed specifications alone.
For consumers, technicians, workshops, and industrial users alike, professional battery testing remains one of the most reliable methods of evaluating battery quality, performance, and long-term value. 🔋
