如果識electronics嘅話就望吓上面幅圖,唔識就唔好理佢
鋰電叉電有2個phase,constant current(CC)同constant voltage(CV)
首先要知道鋰電嘅voltage係4.2V,呢個化學上嘅限制(啲用graphene上到4.35V嘅唔好理住先)
所以叉電嘅時係鋰電最多淨係可以駁4.2V,唔係嘅話overvoltage會爆炸
當你粒電得返3.2V,呢個時候你駁4.2V,ΔV = 4.2 - 3.2 = 1.0V,咁粒電draw緊,比如話10A嘅current先算啦
然後你發現粒鋰電開始出煙同着火
原來叉電係會發熱嘅,發熱量同current嘅二次方成正比
為咗唔好令到粒電着火,唯有限住current,比如話2A咁樣,呢個就係constant current嘅phase
因為voltage同current成正比(即係V=IR),你比得2A佢,ΔV就無1.0V咁多,可能係0.2V咁先算,即係而家駁住粒電嘅得3.2 + 0.2 = 3.4V啦,無4.2V咁多
但係隨住你粒電越叉越滿,比如話叉到4.01V咁,呢個時候因為上面咁講,最多淨係可以畀4.2V俾粒電,咁而家ΔV = 4.2 - 4.01 = 0.99V,用返V=IR,即係你出嘅current就無2A咁多
粒電越滿越接近4.2V,ΔV就越細,current跟住細,所以叉電就越慢
呢個phase因為你keep畀4.2V俾粒電,所以叫constant voltage
P.S. 簡化咗,事實上R同埋ΔV會變,但係唔影響理解個原理
利申:玩過遙控模型嘅鋰電