ASOL 403040 Lithium Polymer Battery — Ultra-compact Lithium Polymer soft pack engineered for miniaturized consumer electronics. At just 4.1mm thin with a 43×30.5mm footprint, this battery integrates seamlessly into sleek wearable and IoT devices. It delivers a reliable 400mAh capacity with 500+ cycle life, making it an ideal long-lasting power solution for TWS earbuds, smartwatches, fitness trackers, BLE beacons, and other space-constrained electronics.
Why Lithium Polymer vs Cylindrical Cells?
Unlike traditional cylindrical batteries (e.g. 18650), lithium polymer soft-pack cells offer decisive advantages for compact consumer devices:
- Thinner Profile — As low as 3mm thickness vs minimum 18mm for 18650
- Flexible Shape — Adapts to custom enclosures, curved designs, and irregular cavities
- Lighter Weight — Up to 30% lighter than equivalent-capacity cylindrical cells
- No Pressure Vents — Safer for ultra-compact devices with limited or no venting
- Higher Energy Density — Maximizes capacity in minimal physical space
- OEM-Friendly Customization — Tabs, wires, connectors, and form factor tailored to your product
Key Features
Tiny soft-pack, market-ready power
4.1×30.5×43mm fits ultra-compact device enclosures.
1.48Wh energy in a tiny soft-pack form factor.
Enables sleek, lightweight product industrial design.
Aluminum-laminated polymer construction, lightweight and flexible.
Extended service life with minimal capacity fade.
UN38.3 certified – market-ready worldwide.
Charge 0~45°C · Discharge -20~60°C.
Tabs, wires, connectors, or fully custom form available.
Safe for air transport; full documentation available.
Specifications
| Parameter | Value |
|---|---|
| Model | 403040 |
| Cell Type | Lithium Polymer (Lithium Polymer) Soft Pack |
| Nominal Voltage | 3.7V |
| Nominal Capacity | 400mAh |
| Energy | 1.48Wh |
| Thickness (T) | 4.1mm (Max) |
| Width (W) | 30.5mm (Max) |
| Length (H) | 43mm (Max) |
| Configuration | 1S1P |
| Impedance | ≥50mΩ |
| Charge Voltage | 4.2V |
| Standard Charge Current | 80mA (0.2C) |
| Max Charge Current | 400mA (1C) |
| Standard Discharge Current | 80mA (0.2C) |
| Max Discharge Current | 400mA (1C, continuous) |
| Discharge Cut-off | 2.5V |
| Charge Temp | 0~45°C |
| Discharge Temp | -20~60°C |
| Storage Temperature | -10~35°C |
| Cycle Life | 500+ cycles (100% DOD, 1C, 25°C) |
| Weight | Approx. 9g |
| Certifications | UN38.3 |
Applications
Where the 403040 is used
TWS earbuds, charging cases & bone-conduction headsets.
Smart watchbands, fitness trackers and sports rings.
BLE beacons, sensors, door/window and key trackers.
Smart styluses, digital notepads, label makers & signature pads.
Pulse oximeters, thermometers and Bluetooth glucometers.
Why ASOL
Factory-direct, fully customizable
Connector, wire gauge, heat-shrink color, custom brand label, BMS & housing.
Integrated PCB against overcharge, over-discharge, overcurrent & short circuit.
Grade-A cells, voltage-matched ±10mV for stable, reliable performance.
Sample evaluation may be available for selected cylindrical and lithium polymer battery projects, subject to specification review and product availability. Sample freight is paid by the customer.
Inspection requirements and acceptance criteria are confirmed for each project before order release.
UN38.3 Class 9 air & sea · DHL/FedEx/UPS · EXW/FOB/CIF/DDP.
Wholesale Pricing
| Quantity | Unit Price | Savings |
|---|---|---|
| 100-499 pcs | Contact us | - |
| 500-999 pcs | Contact us | 8% off |
| 1,000-4,999 pcs | Contact us | 15% off |
| 5,000+ pcs | Contact us | 20%+ off |
Custom specifications are welcome. Sample evaluation may be available for selected cylindrical and lithium polymer battery projects, subject to specification review and product availability. Sample freight is paid by the customer. Full certification documentation provided.
Frequently Asked Questions
What are the key specifications of the ASOL 403040 3.7V 400mAh Lithium Polymer Battery Cell?
The ASOL 403040 3.7V 400mAh Lithium Polymer Battery Cell is a 3.7V 400mAh lithium battery, built in a 1S1P configuration, weighing ~9g.
What is the maximum discharge current of the ASOL 403040 3.7V 400mAh Lithium Polymer Battery Cell?
The ASOL 403040 3.7V 400mAh Lithium Polymer Battery Cell supports a maximum continuous discharge current of 400mA.
What safety certifications does the ASOL 403040 3.7V 400mAh Lithium Polymer Battery Cell have?
It is certified to UN38.3, and full test reports can be provided on request.
Does ASOL offer OEM/ODM customization for the ASOL 403040 3.7V 400mAh Lithium Polymer Battery Cell?
Yes. As a lithium battery manufacturer, ASOL provides full OEM/ODM customization — capacity, voltage, cell configuration, connector type, wire length, and label printing can all be tailored to your application and order volume.
Can I get a sample or a quote for the ASOL 403040 3.7V 400mAh Lithium Polymer Battery Cell?
Yes. Sample evaluation may be available for selected cylindrical and lithium polymer battery projects, subject to specification review and product availability. Sample freight is paid by the customer. Email info@asolbattery.com or message +86 15779858703 on WhatsApp for a quote — ASOL typically responds within 24 hours on working days.
Contact Us
| Channel | Information |
|---|---|
| info@asolbattery.com | |
| +86 157 7985 8703 | |
| Website | www.asolbattery.com |
| Response Time | Within 24 hours on working days |
Need a different size or capacity? Explore ASOL’s full lithium polymer battery range →
