Ampace JP40 21700
4000mAh / 70A-Class
High-power 4.0Ah 21700 lithium-ion cell built for applications that require very high current capability, fast charge support, and strong power density in a compact cylindrical format. This Shopify-ready page converts the product listing and linked specification into a professional, technical, chart-heavy description for customers comparing current rating, voltage behavior, thermal limits, mechanical fit, and pack-design use cases.
Ampace JP40 21700 4000mAh 70A Battery
The Ampace JP40 is a high-output 21700 cell designed for high-discharge applications where a conventional energy cell may sag too heavily or run too hot. Its engineering profile is defined by a 4000mAh standard discharge capacity, 3.7V nominal voltage, rated fast charge capability, low initial impedance, and very high current support.
The current rating is presented in two layers: the product listing name identifies this as a 70A-class battery, while the linked specification defines 45A maximum continuous discharge without triggering an 80°C temperature cut and a 140A 5-second pulse discharge. For actual pack engineering, use the datasheet conditions and validate the final pack under real thermal load.
| Brand / Model | Ampace JP40 / Ampace part number 21700A |
|---|---|
| Cell Type | 21700 cylindrical lithium-ion rechargeable cell |
| Standard Discharge Capacity | Mean 4000mAh |
| Rated Discharge Capacity | Mean 3900mAh at 40A discharge to 2.5V |
| Nominal Voltage | 3.7V |
| Charge Cut-Off Voltage | 4.20V |
| Discharge Cut-Off Voltage | 2.50V |
| Standard Charge | 0.5C / 2A CC-CV to 4.2V, terminate at 80mA |
| Rated Charge | 2C / 8A CC-CV to 4.2V, terminate at 200mA |
| Charging Time | Approx. 140 minutes standard charge; approx. 40 minutes rated charge |
| Standard Discharge | 0.2C / 0.8A CC discharge to 2.5V |
| Max Continuous Discharge | 45A without triggering 80°C temperature cut Use as datasheet design reference |
| Product Listing Rating | 70A-class listing label Validate for end-use |
| Max Pulse Discharge | 140A for 5 seconds at 25±2°C |
| Initial Impedance | ≤4mΩ AC impedance at 1kHz after charge to shipment voltage |
| Dimensions | 21.31mm max diameter × 70.42mm max height, with tube |
| Weight | 70.0g max |
| Charge Temperature | -10°C to 60°C, with recommended recharge release <45°C |
| Discharge Temperature | -30°C to 75°C, with required re-discharge release <60°C |
| Storage Condition | 0°C to 60°C within 1 month; 0°C to 45°C within 3 months; 0°C to 25°C within 12 months; humidity ≤75%RH |
| Shipment Voltage | 3.50V to 3.59V |
| Protection | No — unprotected bare cell |
Electrical operating envelope at a glance.
These quick-reference visuals summarize the cell’s operating window, current layers, capacity-to-energy translation, and C-rate conversion.
1. Current Capability Stack
Product-listing rating, datasheet continuous rating, rated discharge test condition, charge rates, and pulse reference.
2. Voltage Operating Window
Basic per-cell voltage limits used for charger, BMS, and pack configuration.
3. Capacity and Energy Translation
Nominal watt-hours are calculated from standard discharge capacity and nominal voltage.
4. C-Rate Conversion
For a 4000mAh cell, 1C equals approximately 4A.
| 2A | 0.5C standard charge |
|---|---|
| 8A | 2C rated charge |
| 40A | 10C rated discharge capacity test |
| 45A | ≈11.25C datasheet continuous discharge reference |
| 70A | ≈17.5C product listing label |
| 140A | ≈35C, 5-second pulse reference |
High-current output should be evaluated with voltage sag, heat rise, and rating conditions in mind.
The specification defines both standard and high-rate discharge tests. The rated discharge capacity is listed as 3900mAh at 40A, while the rate capability table compares capacity at 0.8A, 20A, 32A, 40A, and 50A after rated charge. This gives the JP40 a strong high-power profile for applications that need more current than a typical energy-focused 21700 cell can comfortably provide.
The simplified discharge graph below is intentionally product-page friendly. It shows expected curve shape and relative voltage sag under heavier current, but it is not a digitized lab test curve. Use it as a visual explanation of current loading, not as a guaranteed runtime graph.
Rate capability summary
| 0.8A | 100% relative capacity reference |
|---|---|
| 20A | 94% relative capacity |
| 32A | 96% relative capacity |
| 40A | 98% relative capacity |
| 50A | 100% relative capacity in published table |
| Design interpretation | Capacity remains comparatively strong under very high discharge currents, but voltage sag and thermal load still increase as current rises. |
5. Simplified Discharge-Curve Graph
Voltage vs. capacity illustration for standard, rated, and high-current operation. Simplified for product-page visualization.
6. Estimated IR Voltage Drop
Using the published ≤4mΩ AC impedance as a rough planning reference. DC pack sag will vary with temperature, state of charge, age, and interconnect resistance.
Temperature, charge current, and discharge load must be managed together.
The linked specification includes low-temperature charge derating, high-temperature charge voltage limitation, discharge temperature behavior, rate capability data, storage criteria, and cycle-life criteria. These controls matter because the JP40 is intended for very high-power operation.
7. Charge Profile Reference
Standard charge is 2A CC/CV to 4.2V; rated charge is 8A CC/CV to 4.2V at the primary temperature range.
8. Temperature-Based Charge Limits
Charge method changes with cell-surface temperature.
| -10°C to <0°C | 0.4A CC to 4.2V, CV to 200mA |
|---|---|
| 0°C to <10°C | 2A CC to 4.2V, CV to 200mA |
| 10°C to <45°C | 8A CC to 4.2V, CV to 200mA |
| 45°C to 60°C | 8A CC to 4.1V |
| System takeaway | Fast charging requires temperature-aware control; high-temperature charging reduces the voltage limit. |
9. Thermal Operating Envelope
Published charge and discharge surface-temperature ranges.
10. Temperature Discharge Capacity
Relative capacity at 40A discharge after rated charge, normalized to 25°C.
11. Discharge Rate Capability
Relative capacity by current after rated charge, as published in the specification.
12. Cycle-Life Visualization
Published cycle criteria: ≥2400mAh after 400 cycles at 30A, and ≥2400mAh after 300 cycles at 40A under stated test conditions.
21700 dimensional envelope for holders, spot-weld fixtures, and pack CAD.
The mechanical dimensions are specified with tube. Use the maximum envelope for holder fit, battery pack CAD, weld fixture clearance, and insulating ring checks.
13. Cell Dimension Diagram
Mechanical envelope based on the linked specification drawing.
14. Pack Scaling Formulas
Quick math for series/parallel planning. Validate current limits thermally and electrically.
Pack Voltage ≈ Series Count × 3.7V
Pack Capacity ≈ Parallel Count × 4.0Ah
Pack Energy ≈ S × P × 14.8Wh
Datasheet Continuous Current ≈ P × 45A
15. Example Parallel Scaling
Approximate scaling using 45A datasheet continuous current reference, not a finished pack guarantee.
| 1P | 4.0Ah, 14.8Wh, 45A datasheet continuous reference |
|---|---|
| 2P | 8.0Ah, 29.6Wh, 90A datasheet continuous reference |
| 3P | 12.0Ah, 44.4Wh, 135A datasheet continuous reference |
| 4P | 16.0Ah, 59.2Wh, 180A datasheet continuous reference |
| 5P | 20.0Ah, 74.0Wh, 225A datasheet continuous reference |
16. Common Series Voltage Examples
Nominal voltage examples only. Full-charge and cut-off pack voltages scale separately.
| 1S | 3.7V nominal / 4.2V full / 2.5V cut-off |
|---|---|
| 3S | 11.1V nominal / 12.6V full / 7.5V cut-off |
| 4S | 14.8V nominal / 16.8V full / 10.0V cut-off |
| 5S | 18.5V nominal / 21.0V full / 12.5V cut-off |
| 10S | 37.0V nominal / 42.0V full / 25.0V cut-off |
| 13S | 48.1V nominal / 54.6V full / 32.5V cut-off |
Use the JP40 inside a temperature-monitored, current-limited electrical system.
The JP40 is a high-power, unprotected bare cell. Professional implementation requires a charger/BMS strategy that respects voltage, current, temperature, and interconnect limits.
17. Suggested Control Threshold Map
System-level control guidance derived from the linked specification.
| Charge upper limit | 4.20V per cell; 4.10V limit in the high-temperature charge band |
|---|---|
| Discharge floor | 2.50V per cell |
| Charge temperature gate | -10°C to 60°C, with current and voltage derating by temperature |
| Discharge temperature gate | -30°C to 75°C surface temperature range |
| Re-discharge release | Allow the cell to cool below 60°C before re-discharge after overheating |
| Continuous current | Use 45A datasheet continuous reference unless the final system is separately validated for a higher rating condition |
18. Risk-Control Checklist
Recommended pack-building and use practices.
- Use only in devices or packs designed for lithium-ion 21700 cylindrical cells.
- Use a BMS or controller that monitors voltage, current, and temperature.
- Do not charge above 4.20V or discharge below 2.50V per cell.
- Derate charging at low and high temperatures according to the temperature table.
- Never carry loose cells with conductive objects such as keys, coins, tools, or metal cases.
- Spot weld for pack assembly; do not solder directly to the cell body.
- Inspect wraps and top insulator rings before use.
- Validate pack busbar, nickel, tab, wiring, fuse, and BMS sizing under real load.
Best suited for high-power systems where current density matters.
Power Tools
- Strong option for compact tool packs where current output is the primary requirement.
- Useful for applications that need high burst current and reduced voltage sag.
Drones / RC
- Good fit for high-load motor systems where power density and compact pack geometry matter.
- Thermal validation is essential at elevated discharge currents.
E-Bike / Mobility
- Suitable for performance packs when paired with proper BMS, fusing, and thermal design.
- Parallel count should be chosen from measured pack current and cooling conditions.
Robotics
- Supports high motor current in compact autonomous or remote-controlled platforms.
- Useful where response, peak power, and high discharge rate are important.
High-Output Lighting
- Appropriate for demanding lighting systems that pull high current from each cell.
- Lower impedance helps reduce voltage drop at high output levels.
Custom Battery Packs
- Designed for experienced builders and integrators who can manage current sharing and heat.
- Requires matched cells, correct welding, insulation, protection, and pack-level qualification.
19. Selection Bias: Power vs. Runtime
Product-page positioning for shoppers comparing high-power and high-energy cells.
20. Application Suitability Matrix
Simple product-page fit guidance.
| Power tools | Strong fit |
|---|---|
| Drones / RC | Strong fit |
| Robotics | Strong fit |
| Performance mobility packs | Validate thermally |
| Maximum runtime per cell | Consider higher-capacity cells |
| Unmanaged consumer devices | Not recommended |
Safety, Handling & Compatibility Notice
This product is an unprotected lithium-ion cell. It should only be used by customers who understand cell-level lithium-ion safety and who are using the battery in compatible hardware, managed packs, or professionally designed assemblies. Improper use can lead to overheating, venting, fire, or explosion.
- Charge only with lithium-ion chargers or managed battery systems designed for the correct chemistry and cell count.
- Never short circuit, crush, puncture, incinerate, or expose the cell to water.
- Do not use cells with damaged wraps, dented cans, or missing top insulator rings.
- Do not mix with cells of different age, capacity, model, or state of charge in the same pack.
- For assembly, use spot welding rather than direct soldering to reduce heat damage risk.
- Store and transport in non-conductive cases; never carry loose cells in pockets or bags.
- Keep away from children and from applications for which the product is not specified.
- Not for e-cigarette, vape, or similar use.
This page is formatted as a technical, chart-oriented Shopify description and is intended to improve customer understanding. Final device compatibility and safety remain the responsibility of the integrator or end user.
Common technical questions about the Ampace JP40.
What is the capacity of the Ampace JP40?
The linked specification lists a mean standard discharge capacity of 4000mAh and a mean rated discharge capacity of 3900mAh at 40A discharge to 2.5V.
Is this a 70A battery?
The product listing identifies the cell as 70A-class. The linked specification defines 45A maximum continuous discharge without triggering the 80°C temperature cut and 140A pulse discharge for 5 seconds. For engineering design, use the datasheet conditions and validate the complete pack under load.
What is the maximum pulse current?
The specification lists a maximum pulse discharge of 140A for 5 seconds at 25±2°C.
Is this a protected battery?
No. This is an unprotected bare 21700 cell and should only be used in systems with appropriate voltage, current, short-circuit, and temperature protection.
What charger should be used?
Use a lithium-ion charger or battery-management system that uses a CC/CV profile to 4.20V per cell. The standard charge is 2A, while the rated charge is 8A under the appropriate temperature range.
Can the JP40 fast charge?
Yes. The rated charge method is 8A CC/CV to 4.2V with 200mA termination. The charge current must be derated by temperature, especially below 10°C and above 45°C.
What is the correct discharge cut-off voltage?
The specification states a 2.50V discharge cut-off voltage per cell. Many pack designers choose a higher system cut-off to reduce stress and improve service life.
Can the JP40 be used in battery packs?
Yes. It is well suited to custom high-power packs when cell matching, spot welding, thermal monitoring, fusing, BMS sizing, and current sharing are properly engineered.
Can I solder wires directly to this cell?
Direct soldering is not recommended. Spot welding is the preferred pack-assembly method because it reduces the risk of heat damage to the cell.
What are the cell dimensions?
The maximum published dimensions are 21.31mm diameter and 70.42mm height, with tube included.
What temperature range is allowed?
The specification lists -10°C to 60°C for charging and -30°C to 75°C for discharging. Charging current and voltage are temperature dependent, so a managed system should enforce the appropriate derating profile.
What does ≤4mΩ internal impedance mean?
It indicates a very low-impedance high-power cell, which helps reduce voltage sag under load. Real pack resistance also includes welds, nickel, busbars, wiring, holders, and BMS components.
How many cycles should I expect?
The linked specification gives two high-load cycle criteria: capacity of at least 2400mAh after 400 cycles at 30A discharge, and at least 2400mAh after 300 cycles at 40A discharge under the stated test conditions. Actual service life depends on current, temperature, depth of discharge, and charge limits.
Can I carry this battery loose?
No. Loose transport is unsafe because conductive objects can short the terminals. Always use a non-conductive battery case.