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.
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 |
These quick-reference visuals summarize the cell’s operating window, current layers, capacity-to-energy translation, and C-rate conversion.
Product-listing rating, datasheet continuous rating, rated discharge test condition, charge rates, and pulse reference.
Basic per-cell voltage limits used for charger, BMS, and pack configuration.
Nominal watt-hours are calculated from standard discharge capacity and nominal voltage.
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 |
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.
| 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. |
Voltage vs. capacity illustration for standard, rated, and high-current operation. Simplified for product-page visualization.
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.
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.
Standard charge is 2A CC/CV to 4.2V; rated charge is 8A CC/CV to 4.2V at the primary temperature range.
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. |
Published charge and discharge surface-temperature ranges.
Relative capacity at 40A discharge after rated charge, normalized to 25°C.
Relative capacity by current after rated charge, as published in the specification.
Published cycle criteria: ≥2400mAh after 400 cycles at 30A, and ≥2400mAh after 300 cycles at 40A under stated test conditions.
The mechanical dimensions are specified with tube. Use the maximum envelope for holder fit, battery pack CAD, weld fixture clearance, and insulating ring checks.
Mechanical envelope based on the linked specification drawing.
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
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 |
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 |
The JP40 is a high-power, unprotected bare cell. Professional implementation requires a charger/BMS strategy that respects voltage, current, temperature, and interconnect limits.
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 |
Recommended pack-building and use practices.
Product-page positioning for shoppers comparing high-power and high-energy cells.
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 |
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.
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.
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.
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.
The specification lists a maximum pulse discharge of 140A for 5 seconds at 25±2°C.
No. This is an unprotected bare 21700 cell and should only be used in systems with appropriate voltage, current, short-circuit, and temperature protection.
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.
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.
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.
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.
Direct soldering is not recommended. Spot welding is the preferred pack-assembly method because it reduces the risk of heat damage to the cell.
The maximum published dimensions are 21.31mm diameter and 70.42mm height, with tube included.
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.
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.
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.
No. Loose transport is unsafe because conductive objects can short the terminals. Always use a non-conductive battery case.
Overall rating: 4.9 / 5 from 24 reviews.
I used these AMPACE cells to rebuild a Kobalt Ultimate Output 24v battery. The cells all charged and tested above stated output and functioned perfectly. With these cells installed I believe the battery truly is an Ultimate Output battery. The package came well packed and the shipping was fast. I have been very satisfied with the 18650 Battery Store's service and communications and service. They answer any questions I have and are pleasant to deal with.
❤️
I love these cells. Built a few DeWalt flexvolt batteries with them and they really perform well. I just wish they were a little cheaper.
These cells have great capacity. Unfortunately I ruined 3 of them learning that their NO-GO area for spot welding on the negative end is larger than other cells. I was building an M18 pack and had to go outside the pre-made welding tabs on the negative side to avoid punctures and letting the "fizz" out. Be careful when you welding the negative on these and steer way clear of the center.
Just like in the photos, and fast delivery—thanks.
Great value great batteries
Thanks, fast shipped and good product
Great batteries! And shipping was fast !
Great batteries. Fast shipping. Great price
Received cells packaged and balanced well. Theses cells worked perfectly for my build.
Batteries arrived quick and as ordered.
Awesome product and Super Awesome company
N
Great quality
Great experience, shipped quick, batteries great condition
Both batteries that I ordered met their output claims. Very happy with how they work in my flashlights.
Easy purchase. Fast shipping.
These batteries are absolutely amazing! The 70amp output is no joke. With a 6S pack my 5", 7" and 10" quadcopters run just as if I were using lipos. No perceptible voltage sag even with aggressive freestyle flying with the 5" and 7" quads. The 10" quad pulls 80amps per motor so I've only cruised and flown cinematically with these batteries. It handles that just fine. The performance of these cells has been so incredible that I don't think I'll ever purchase a 6S lipo pack again!
Powerful Battery! But...It it reminds me of Lipo batteries. When you reach 3v the power falls off a cliff.
I'm impressed! These batteries hit hard and last a long while.
love it, i got exactly what i paid for. im always skeptical of ordering products from random online vendors but these ppl are legit.
Great batteries
Just now making a 6s1p battery pack. There are no reviews on this battery here but several Youtube reviewers rate this battery very high. I have been waiting for it to come back into inventory for many weeks and grabbed some. Supposed to be one of the best. We shall see.
