BAK 45D: High-Power 21700 Cells for Performance eBike Batteries
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As the eBike industry continues to push toward higher performance, battery cells must deliver strong discharge capability, thermal stability, and reliable cycle life. One manufacturer gaining attention in this space is BAK Power Battery, particularly with its 21700 high-discharge cells like the 45D.
At Bicycle Motor Works, understanding how emerging cells like the BAK 45D perform is critical when building high-output battery systems.
Who Is BAK Power Battery?
BAK Power Battery Co., Ltd. is a Chinese lithium-ion battery manufacturer founded in 2001. The company specializes in:
Cylindrical lithium-ion cells (18650, 21700, 4680)
EV battery systems
Energy storage solutions
Micro-mobility applications (eBikes, scooters)
BAK has supplied cells to:
Electric vehicle manufacturers
Power tool brands
Light electric mobility companies
What distinguishes BAK:
Large-scale automated production
Focus on high-power cylindrical cells
Competitive positioning against Samsung, LG, and EVE
BAK 45D: High-Discharge 21700 Cell
The BAK INR21700-45D is designed as a high-power cylindrical lithium-ion cell, competing directly with cells like:
Samsung 45T
Molicel P45B
Ampace JP40
Key Specifications (BAK 45D)
Format: 21700 cylindrical
Capacity: 4500mAh (4.5Ah)
Nominal Voltage: 3.6V
Energy: ~16.2Wh
Max Continuous Discharge: ~45A
Peak Discharge: ~60A+ (short bursts)
Max Charge Current: ~6A–8A
Sources:
BAK Power Battery datasheet (INR21700-45D)
Industry battery specification databases
Third-party comparative testing
What Defines the BAK 45D?
The 45D sits in a category of:
👉 High-capacity, high-discharge hybrid cells
This means it aims to deliver:
Strong current output
Increased capacity over 4.0Ah-class cells
Balanced performance across power and range
Performance Characteristics
1. High Discharge Capability
With a ~45A continuous rating, the 45D is built for:
High-performance eBike systems
High-watt controllers (2000W–5000W+)
Demanding acceleration and torque loads
This places it alongside top-tier power cells like:
Samsung 45T
Molicel P45B
2. Increased Capacity vs 40T-Class Cells
At 4500mAh, the 45D provides:
~12–15% more capacity than 4000mAh cells
This results in:👉 Slightly longer range without sacrificing power
3. Voltage Stability Under Load
Cells in this category are engineered for:
Reduced voltage sag
Consistent output under high current
While independent testing is more limited compared to Samsung or Molicel, available data suggests:
Competitive performance in high-drain scenarios
4. Thermal Performance
High-power cells inherently generate heat, but the 45D is designed to:
Maintain stable operation under load
Operate safely within specified discharge limits
However:👉 Proper pack design and cooling remain essential
BAK 45D vs Other High-Power Cells
Cell | Capacity | Continuous Discharge | Focus |
BAK 45D | 4.5Ah | ~45A | Power + capacity |
Samsung 45T | 4.5Ah | ~45A | Proven power |
Molicel P45B | 4.5Ah | 45A | Premium performance |
Ampace JP40 | 4.0Ah | ~60A | Extreme power |
Key Takeaways
45D matches 45T-class performance on paper
Offers higher capacity than 40T-class cells
Positioned as a competitive alternative in high-power builds
Real-World eBike Applications
Best Use Cases for BAK 45D
1. High-Performance Builds
2000W–5000W+ systems
High-current controllers
Aggressive riding styles
2. Balanced Power + Range Systems
Riders who want both:
Strong acceleration
Decent range
3. Cost-Performance Builds
Builders looking for:
High output capability
Competitive pricing vs premium brands
Engineering Considerations for Bicycle Motor Works
1. Pack Design
Using 45D allows:
Fewer parallel groups vs 4.0Ah cells
Improved energy density in high-power packs
2. Thermal Management
Because of high discharge capability:
Heat generation is significant under load
Requires:
Proper spacing
High-quality nickel or busbar connections
Effective airflow or heat dissipation
3. Voltage Sag Behavior
Cells in this category are designed to:
Maintain voltage under high load
However:
Premium cells like Molicel may still outperform in extreme conditions
Where BAK Fits in the Industry
BAK is part of a growing group of manufacturers competing with established leaders:
Competes With:
Samsung SDI
LG Energy Solution
Molicel
EVE Energy
Ampace
Strengths
Competitive pricing
Solid performance specifications
Expanding production scale
Considerations
Less long-term performance data than Samsung or Molicel
Independent testing is more limited
Real-world validation varies by batch and supplier
Why BAK 45D Matters for eBike Batteries
The 45D reflects a broader industry trend:
1. Hybrid Power Cells Are the Future
Cells are no longer just:
High power OR high capacity
They are becoming:👉 Both
2. Increased Competition Drives Innovation
More manufacturers mean:
Better pricing
Faster development cycles
More options for builders
3. Expanding Supply Chains
BAK contributes to:
Diversifying global battery supply
Reducing reliance on a few dominant brands
Final Thoughts
The BAK 45D is a strong contender in the high-performance 21700 cell category, offering:
High discharge capability (~45A)
Increased capacity (4.5Ah)
Balanced power and range
For Bicycle Motor Works, it represents:
A viable option for high-output battery systems
A competitive alternative to Samsung and Molicel
A flexible solution for performance-focused riders
Summary
BAK 45D = Power + capacity hybrid cell
Suitable for high-performance eBike builds
Competes with Samsung 45T and Molicel P45B
Best used in properly engineered high-current battery packs
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