18V 3Ah Li-ion Battery Pack for Cordless Electric Screwdriver
In May 2025, a precision assembly tool manufacturer approached CMB with a challenging battery pack requirement. They needed a lightweight, high C-rate battery pack capable of handling the extreme current spikes generated during screwdriver stall events without triggering unnecessary BMS shutdowns.
The new battery also had to fit the customer’s existing proprietary connector housing supplied by their previous vendor, allowing a true drop-in replacement with no changes to the tool design.
Within just 35 days, CMB designed, validated, and delivered a custom 5S3P 18V 3Ah lithium-ion battery pack that met all performance, mechanical, and production requirements.
Customer Overview
The customer is an electronics manufacturing OEM based in Southeast Asia, producing cordless electric screwdrivers used in furniture manufacturing and SMT (Surface Mount Technology) assembly lines.
Their production operates 24/7 in three shifts, with each operator driving more than 200 screws per shift, making battery reliability a critical factor in overall production efficiency.
18V 3Ah 18650 Electric Screwdriver Battery Pack Design
Product Highlights
- Cell configuration: 5S3P (INR18650 15 cells)
- Max continuous discharge: 20 C
- Peak / stall current: 60A — 80 ms delay window before BMS trips
- Stall detection delay: 80 ms (prevents nuisance trips)
- Short-circuit response: <200 µs cut-off
- Cell balancing: Passive, ±20 mV tolerance
- Temperature protection: 45°C charge / 60°C discharge cutoff
- 25% Weight reduction vs previous 4Ah pack
- Cycle life: ≥500 cycles @ 80% DoD
| No. | Item | Specification | Note |
|---|---|---|---|
| 1 | Nominal Voltage | 18V | 3.6V/Cell |
| 2 | Nominal Capacity | 3Ah | @0.2C |
| 3 | Minimum Capacity | ≥2.9Ah | / |
| 4 | Initial Internal Impedance | ≤60mΩ | AC 1KHZ |
| 5 | Standard Charge Voltage | 21V | 4.2V/Cell |
| 6 | Standard Charge Current | 2A | @0.2C |
| 7 | Max Charge Current | 4A | BMS Limit |
| 8 | Standard Discharge Current | 15A | @0.2C |
| 9 | Max. Discharge Current | 60A | / |
| 10 | Discharge Cut-off Voltage | 13.75V | 2.5V/Cell |
| 11 | Cycle Life | ≥500 cycles | Retention: ≥80% |
| 12 | Charge Temperature | 0°C~45°C | Standard Charge |
| 13 | Discharge Temperature | -20°C~60°C | Standard Discharge |
| 14 | Storage Temperature | -20°C~ 45°C | ≤3 Months |
| 0°C ~ 25°C | ≤1 Year | ||
| 15 | Weight | About 420g | / |
FAQs-18V 3Ah Li-ion 18650 Battery Pack for Cordless Screwdriver
My screwdriver BMS trips when the fastener binds. Can this be fixed at the battery level?
Yes. The stall current spike is a well-understood failure mode in screwdriver applications. The fix is a BMS with a configurable over-current delay window (typically 50–100 ms) that holds the output live during the spike rather than treating it as a fault. CMB tunes this window to match your motor’s stall profile during sample validation.
We already use a 4Ah pack from another supplier. Why would we switch to 3Ah?
If your operators rotate packs every 1.5–2 hours anyway, the extra 1Ah of the 4Ah pack is unused capacity that just adds ~140g of carry weight all day. For precision screwdriving tasks, that weight difference accumulates into measurable wrist fatigue. The 3Ah is purpose-built for high-cycle, lower-duration sessions.
What is the minimum order quantity for a custom housing and connector?
We support low-volume as well as large-scale production projects. MOQ requirements for custom housings and connectors vary depending on the design and tooling requirements. Please contact us with your project details, and our engineers will provide the most suitable solution and quotation.
What discharge rate does a cordless screwdriver actually require?
Continuous run load is typically 8–12C for professional screwdrivers. The 15–20C rating of this pack provides a comfortable headroom buffer for stall events without the cells entering stress territory. Using an oversized C-rate also lowers cell operating temperature at normal load, which directly extends cycle life.
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