1. Identify application scenarios
The purpose of lithium batteries directly affects parameter selection:

• Portable devices (mobile phones, drones, cameras): give priority to high energy density (such as ternary lithium batteries) and lightweight.
• Electric vehicles/power tools: require high discharge rate (C-rate) and long cycle life (such as lithium iron phosphate batteries).
• Energy storage systems (solar energy, home backup power): focus on high capacity, long life and safety (lithium iron phosphate is more suitable).
• DIY projects/special equipment: need to take into account size, voltage compatibility and customization requirements.

2. Analysis of key parameters
Voltage (V)

• The nominal voltage of a single lithium battery is usually 3.7V (ternary lithium) or 3.2V (lithium iron phosphate).
• Select the number of series cells according to device requirements (such as 48V and 72V are commonly used in electric vehicles).

Capacity (Ah) and energy (Wh)

• Capacity (Ah): determines the battery life. For example, a 10Ah battery can be used for 2 hours at 5A discharge.
• Energy (Wh) = Voltage × Capacity: directly reflects the total energy storage capacity. When comparing different batteries, Wh is more accurate.

Discharge rate (C-rate)

• Indicates the discharge capacity of the battery. For example, 1C means that the battery is fully discharged in 1 hour, and 10C means that the battery is fully discharged in 6 minutes.
• High-power equipment (such as electric drills and drones) requires high-discharge rate batteries (such as 20C or above).

Cycle life

• Ternary lithium battery: about 500-1000 cycles (capacity drops to 80%).
• Lithium iron phosphate battery: 2000-5000 cycles, suitable for long-term use scenarios.

3. Battery type selection

• Ternary lithium battery (NMC/NCA)

o Advantages: high energy density (200-300Wh/kg), good low temperature performance (-20℃).
o Disadvantages: low safety (circuit protection required), short life.
o Applicable: consumer electronics, electric vehicles, drones.

• Lithium iron phosphate battery (LiFePO₄)

o Advantages: high safety (high temperature resistance, non-flammable), long life, and gradually decreasing cost.

o Disadvantages: low energy density (90-160Wh/kg), poor low temperature performance.

o Application: energy storage system, electric bus, low-speed electric vehicle.

• Other types: lithium titanate (ultra-long life), lithium cobalt oxide (high energy, used in mobile phones), etc., selected according to special needs.

4. Safety considerations

Protection circuit: Ensure that the battery has overcharge, over-discharge, and short-circuit protection.

Thermal management: Large-capacity battery packs need to be equipped with heat dissipation design (such as electric vehicle battery packs).

Certification standards: Choose products certified by UL, CE, UN38.3, etc. to avoid inferior batteries.

5. Balance between brand and budget

• Well-known brands: such as CATL, BYD, Panasonic, LG Chem, etc., with guaranteed quality.
• Cost-effectiveness:

o Low-priced batteries may use second-hand cells or inferior BMS (battery management system).
o Lithium iron phosphate has a high initial cost, but is more cost-effective in the long run (long cycle life).

6. Physical and environmental factors

• Size and weight: Make sure the battery can be installed in the device (e.g. drones are sensitive to weight).
• Temperature range:

o High temperature environment: Choose high temperature resistant cells (e.g. LiFePO₄).
o Low temperature environment: Ternary lithium batteries perform better, or add a heating system.

7. Regulations and environmental protection

• Transportation restrictions: Large-capacity batteries may be subject to air transportation restrictions (e.g. more than 100Wh need to be declared).
• Recycling: Choose a brand that supports recycling to avoid environmental pollution.

Summary of steps
1. Clear purpose: Determine the device type and core requirements (e.g. endurance, power, life).
2. Calculate requirements: Estimate the required voltage and capacity (Wh) based on the device power and operating time.
3. Choose type: Ternary lithium (high energy density) vs. lithium iron phosphate (high safety).
4. Verify safety: Check protection functions, certifications, and user reviews.
5. Budget matching: Select the best model within the acceptable range of brand and quality.
6. Installation adaptation: Confirm size, weight, and environmental adaptability.

Example scenarios:

• Electric vehicle modification: Select 72V 20Ah lithium iron phosphate battery (long cycle life and high safety).
• Outdoor power supply: Select 12V 100Ah LiFePO₄ battery (supports 2000 cycles, suitable for long-term energy storage).
• Drone: Select high-rate ternary lithium battery (such as 4S 1500mAh 75C).

Through the above steps, you can systematically screen out the lithium battery solution that best suits your needs.