Lithium-ion Battery Selection Guide for Power Tools

Cordless power tools such as drills, impact screwdrivers, angle grinders, and gardening equipment rely on high-performance lithium-ion battery packs for proper operation.

Selecting an unsuitable battery may result in reduced power output, excessive heat generation, shortened service life, or potential safety risks.

This guide provides a reference for selecting lithium-ion batteries for power tools. It is intended for product engineers, manufacturers, OEM/ODM buyers, and end users evaluating battery specifications.

1. Common Lithium Battery Voltage Platforms for Power Tools

Most power tool battery packs are built using 18650 or 21700 lithium-ion cells, connected in series and parallel to achieve the required voltage and capacity.

“20V Max” refers to the maximum charging voltage, not the nominal operating voltage. The actual working voltage of a 5S lithium-ion battery is approximately 18V.

The 18V (5S) platform remains the most widely adopted standard in professional power tools worldwide.

2. Capacity Selection by Tool Type

2.1 Electric drill and screwdriver

Typical Configurations

• Household / DIY tools: 12V 2.0Ah

• Professional drills: 18V 2.0–3.0Ah

2.2 Impact screwdrivers and wrenches

Technical Note:
Factory testing shows that torque loss is more often caused by insufficient discharge capability rather than insufficient capacity (Ah). A battery with adequate capacity but limited discharge performance may fail to deliver stable torque under load.

Design considerations for grinder battery packs typically include:

• Reinforced current paths

• Thermal dissipation optimization

• High-current BMS design

2.4 Garden and Industrial Power Tools

3. Key factors other than voltage and capacity

3.1 Discharge Capability vs. Capacity (Ah)

Capacity alone does not determine tool performance. Batteries with high capacity but low discharge rates may experience voltage sag under high load conditions.

Factory Test Example

• 18V 5.0Ah (low discharge rate): noticeable voltage drop

• 18V 4.0Ah (high discharge rate): stable output

This highlights the importance of cell discharge characteristics in high-power tools.

3.2 Battery Management System (BMS)

A standard power tool BMS typically includes:

• Overcharge protection

• Over-discharge protection

• Overcurrent protection

• Short-circuit protection

• Temperature monitoring

For OEM projects, BMS logic and communication protocols can be customized according to system requirements.

3.3 Cell Quality and Consistency

To ensure stable performance and cycle life, lithium battery packs typically undergo:

• Incoming material inspection

• Capacity grading

• Internal resistance matching

• Aging and reliability testing

These processes help improve:

• Cycle life consistency

• Operational safety

• Batch-to-batch stability

4. Typical Power Tool Battery Configurations

From a factory's perspective, professional buyers should always confirm the following:

1️⃣ Electrical Parameters

✔ Nominal voltage (S configuration)

✔ Rated capacity (Ah)

✔ Maximum continuous & peak current

✔ Charging voltage & current

2️⃣ Cell & Pack Design

✔ Cell brand & model

✔ Cell configuration (S × P)

✔ Cell fixing method (holders / adhesive / laser welding)

✔ Thermal management design

3️⃣ BMS & Safety

✔ BMS current rating

✔ Temperature protection points

✔ Communication protocol (if required)

✔ Balancing function

4️⃣ Certifications & Compliance

✔ UN38.3

✔ MSDS

✔ IEC / UL (if required by market)

✔ Factory quality system (ISO9001 / ISO14001)

5️⃣ Customization Capability (Very Important)

✔ Housing design

✔ Connector type

✔ Label & branding

✔ Firmware logic

✔ Charge compatibility

6️⃣ Manufacturing & Quality Control

✔ Incoming cell inspection

✔ Aging & capacity testing

✔ Load testing

✔ Traceability system

Selecting a lithium battery for power tools requires evaluation beyond nominal voltage and capacity. Discharge performance, cell quality, thermal design, BMS architecture, and manufacturing control all directly influence safety, lifespan, and output stability.

Battery reliability is determined by the combined effect of:

• Cell quality

• Discharge system design

• Battery management strategy

• Manufacturing consistency

About the Manufacturer

Shenzhen First Power Energy Co., Ltd. provides lithium battery solutions for global customers, focusing on power tool applications that require stable performance, safety compliance, and long-term reliability.