"Voltage/capacity/energy density: Understand the three most critical parameters of lithium batteries, you can really understand the battery performance!"
First:Voltage: the "blood pressure" of the battery, which determines the limit of energy output
【 Core Concepts 】
Voltage: The potential difference generated by the movement of unit charge inside the battery, which directly affects the power supply ability of the device
Nominal voltage: the voltage when the battery is working normally (such as 3.7V lithium)
Discharge cutoff voltage: The lowest voltage at which a battery can be safely discharged (usually 2.5-3.0V)
【 Fatal mistake 】
Higher voltage = higher energy?
→ Wrong! Voltage only reflects the intensity of a single discharge, actual energy = voltage x capacity (Wh)
→ Comparison: 5V/2000mAh=10Wh VS 3.7V/5000mAh=18.5Wh
[Real case] A brand of drone crash in 2019:
→ The nominal voltage of the battery is nominal to 4.2V (standard 3.7V), and continuous discharge causes the electrolyte to boil and explode
Second, capacity: the "meal" of the battery determines the nature of the battery life
【 Core formula 】
Capacity (mAh) = Discharge current (mA) × time (h)
【 In-depth analysis 】
Capacity test standard: 0.5C discharge: discharge at half of the rated capacity to the cut-off voltage (such as 500mA discharge for 1000mAh batteries)
Low temperature capacity attenuation: lithium iron phosphate capacity decreases by 40% at -20℃, while ternary lithium only decreases by 15%
"Dummy label" trap
A treasure burst charging treasure measured:
→ Nominal 20000mAh, actual 0.5C discharge only 6300mAh (nominal rate 63%)
→ Key metrics: See if marked "mAh@2A" or "20W output"
Capacity and life game
Deep charge and deep discharge vs Shallow charge and shallow discharge:
→ Comparison of capacity retention rate after 100 full charge and discharge cycles:
Depth charge and discharge: 65%
20%-80% range charge and discharge: 92%
Third, energy density: the "weight loss champion" of the battery, which determines the portability of the device
【 Core formula 】
Energy density (Wh/kg) = Voltage (V) × capacity (Ah)/mass (kg)
Fourth, consumers must see the parameter selection guide
Mobile phone/tablet: 4000mAh +3.8V + voltage is preferred
Be vigilant below 20000mAh +3.2V (mostly low-end cells)
Electric bicycle: pay attention to the energy density above 60Wh/kg (the new national standard requirements ≥50Wh/kg)
Select 18650 cells
Power bank: Calculate the actual energy: capacity (mAh)× voltage (V)/1000 → 20000mAh/3.7V=74Wh
2023 civil aviation restrictions: ≤100Wh can be directly boarded, 100-160Wh requires the approval of the airline
Voltage is the "vital sign" of lithium batteries, capacity is the "meal amount", and energy density is the "body type". By understanding these three parameters, you can see through the hype and make smarter choices. When solid-state batteries break through the energy density bottleneck, perhaps we will witness a real energy revolution - after all, who can master the balance of these three parameters, who will hold the lifeblood of the technology industry in the next decade.
