18650 電池保護板測試（單顆、2串連、3串連、4串連保護板測試）18650 battery protection board test. 

1）僅DIY實驗用，非教學，實作請詢問專業人員，避免危險。
Only for DIY experiment, not for teaching, please ask professionals to avoid danger.
2）本影片主題：單顆18650、2串18650、3串18650、4串18650保護板測試。
防止18650電池過充、過放造成電池損壞。
The theme of this video: single 18650, 2 series 18650, 3 series 18650, 4 series 18650 protection board test.
Prevent 18650 battery from overcharging and over-discharging from causing battery damage.