6500mAh 21700 Battery Comparison: BAK N21700CX-65E vs FEB 21700G/68E vs Amprius SA112
6500mAh 21700 battery comparison evaluates three high-capacity models based on their official specification sheets: BAK N21700CX-65E, FEB 21700G/68E, and Amprius SA112. Although all three offer a typical capacity of 6500mAh, they differ significantly in charge rates, temperature-dependent discharge limits, and internal resistance (AC-IR). Therefore, choosing the best 6500mAh 21700 cell requires a careful look beyond just the mAh rating.
6500mAh 21700 Spec Comparison Table
| Model | Nominal V | Capacity | Max Charge | Max Discharge | AC-IR | Weight |
|---|---|---|---|---|---|---|
| BAK N21700CX-65E | 3.5V | 6350mAh (Rated) 6500mAh (Typical) | 12.7A | 19.05A | ≤8mΩ | ≤75g |
| FEB 21700G/68E | 3.6V | 6500mAh (Min/Typ) | 4.55A (0.7C) *Temp dependent | 13A (2C) *Temp dependent | ≤19mΩ | ≤75g |
| Amprius SA112 | 3.46V | 6350mAh (Min) 6500mAh (Typical) | 4.55A (0.7C) | 13A Continuous 26A Pulse (≤30s) | ≤22mΩ (@30% SOC) | 72±1g |
BAK N21700CX-65E: Highest Charge and Lowest Listed AC-IR
The BAK N21700CX-65E datasheet lists a nominal voltage of 3.5V, with a rated capacity of 6350mAh and a typical capacity of 6500mAh. Additionally, this cell stands out in the group with a 12.7A maximum charge current and a 19.05A maximum discharge current. Specifically, it features the lowest listed AC-IR at ≤8mΩ (measured at 1kHz). Furthermore, BAK specifies a 25°C cycle life of ≥80% capacity after 501 cycles, alongside safe surface temperature limits of 65°C for charging and 80°C for discharging.
FEB 21700G/68E: Temperature-Dependent Performance
Meanwhile, the FEB 21700G/68E offers a nominal voltage of 3.6V and a guaranteed minimum capacity of 6500mAh. However, its maximum continuous charge and discharge currents are strictly temperature-dependent. For example, it allows a maximum charge of 4.55A (0.7C) between 15°C and 45°C, while the 13A (2C) max discharge is only achievable between 0°C and 35°C. Consequently, FEB lists the AC-IR at ≤19mΩ (1kHz) and recommends keeping surface temperatures ≤60°C during charge and ≤70°C during discharge to maintain performance.
Amprius SA112: High Energy Density with 30s Pulse
In contrast, the Amprius SA112 datasheet shows a nominal voltage of 3.46V, with a typical capacity of 6500mAh and a minimum of 6350mAh. Moreover, it has the highest energy density in this group at 315 Wh/kg (weighing just 72±1g). Its maximum charge current is 4.55A (0.7C). For discharge, it lists a 13A (2C) maximum continuous current and a 26A (4C) maximum pulse current explicitly limited to ≤30 seconds. Furthermore, its AC-IR is ≤22mΩ, measured specifically at 30% SOC.
Key Differences
Voltage and capacity ratings vary slightly across the three models. While FEB lists a standard 3.6V nominal voltage and 6500mAh minimum, BAK lists 3.5V with a 6350mAh rated capacity. Amprius has the lowest nominal voltage at 3.46V.
Charge current capabilities are heavily polarized. BAK N21700CX-65E lists 12.7A, far exceeding FEB and Amprius, which both cap at 4.55A (0.7C).
Discharge limits also differ significantly. BAK leads with 19.05A. Although FEB and Amprius both list 13A continuous, FEB strictly limits this to cell temperatures between 0°C and 35°C. By contrast, Amprius adds a 26A pulse rating (≤30s), which FEB does not offer.
Which 6500mAh 21700 Should You Choose?
If you need the highest charge current and lowest listed AC-IR, the BAK N21700CX-65E is the clear choice. For a standard 3.6V platform, consider the FEB 21700G/68E, provided you can manage its temperature-dependent discharge limits. When weight and energy density are critical, the Amprius SA112 delivers strong performance with occasional short bursts up to 26A. Ultimately, the best choice depends on your specific continuous current, thermal design, and cycle life requirements.
FAQ
Are all 6500mAh 21700 batteries the same?
No, they differ significantly in nominal voltage, charge current, and temperature-dependent discharge limits.
Which of these has the highest continuous discharge rating?
The BAK N21700CX-65E lists 19.05A. Both FEB and Amprius list 13A continuous, though FEB’s rating relies on specific temperature conditions.
Which model has the lowest AC-IR?
BAK N21700CX-65E is listed at ≤8mΩ. In comparison, FEB is ≤19mΩ, and Amprius is ≤22mΩ, though Amprius specifies its measurement at 30% SOC.
Can I use the Amprius 26A pulse rating for long periods?
No. The Amprius datasheet explicitly limits the 26A pulse rating to 30 seconds or less.
Conclusion
In this 6500mAh 21700 battery comparison, BAK N21700CX-65E leads on charge current, continuous discharge, and listed AC-IR. Meanwhile, FEB 21700G/68E offers a standard 3.6V platform but requires thermal management to maintain its 13A max discharge. Amprius SA112 provides the highest energy density and a specific 26A pulse rating for burst applications. Therefore, always compare temperature derating, AC-IR test methods, and cycle life before qualifying any cell for your pack.
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