蓄電池作為能量(liang)的轉存裝置或備用(yong)電(dian)源(yuan)被廣(guang)泛地應用于各種(zhong)自動化設備中。使用普通的充電器對(dui)蓄電池充電容易發生過充電或充電不足的現象。過充電，可使蓄電池發熱，電解液失水；充電不足，可使蓄電池內化學反應不充分，并且長期充電不足會導致蓄電池容量下降。以上兩種情況都會降低蓄電池的使用壽命。由此可見，充電器性能的好壞直接影響到蓄電池的使用效果和使用壽命。本文采用恒流限壓、實時監測的智能控制充電方法設計了一種對講(jiang)機所使用的8．41V3Ah的鎳鎘智能充電器一原理完全可設計出用于其他不同類型、不同容量的蓄電池的充電器。

　　1 鎳鎘電池的發展及特(te)點
    
       1899年，Waldmar Jungner首(shou)先在開口型鎳(nie)鎘蓄電弛中使(shi)用了鎳(nie)極板，同(tong)時，Thomos Edison發明(ming)了(le)用于電動(dong)車的(de)鎳鐵電池。但是．由于(yu)當(dang)時這些(xie)堿性蓄電池(chi)的極(ji)板材料比其(qi)他蓄電池(chi)的材料貴得(de)多，其(qi)實際應用受到(dao)了極(ji)大的限(xian)制。直到(dao)1932年，鎳(nie)鎘電(dian)池(chi)(chi)經歷了最重要的改(gai)進：科(ke)學家在鎳(nie)電(dian)池(chi)(chi)中開始使用活性物(wu)質(zhi)。1947年，密封型鐮(lian)鎘電

池研制(zhi)成功。

　　鎳鎘電池的特點是效率高、循環壽命長、能量密度大、體積小、重量輕、結構緊湊、不需要維護，因此在工業和消費產品中得到了廣泛應用。

　　2 鎳鎘電池的充電方(fang)式及充電特(te)性(xing)曲(qu)線
   
       充電器能否達到最佳充電效果由所選擇的充電方式和充電特性曲線共同決定。近年來，蓄電池充電器大致可(ke)以分為(wei)連續電流(liu)充電和脈沖電流(liu)充電兩大類。

　　連續電(dian)(dian)流(liu)充(chong)(chong)電(dian)(dian)因放(fang)電(dian)(dian)容(rong)量受到(dao)(dao)電(dian)(dian)池(chi)接受能力的(de)(de)限制(zhi)和受到(dao)(dao)在充(chong)(chong)電(dian)(dian)過(guo)程中電(dian)(dian)池(chi)極(ji)化所產生氣體(ti)的(de)(de)阻力，使得在大電(dian)(dian)流(liu)充(chong)(chong)電(dian)(dian)的(de)(de)情況下，電(dian)(dian)池(chi)放(fang)電(dian)(dian)容(rong)量下降(jiang)和電(dian)(dian)池(chi)發熱(re)；若用小電(dian)(dian)流(liu)充(chong)(chong)電(dian)(dian)，雖(sui)可(ke)克服這個缺點，但充(chong)(chong)電(dian)(dian)時間過(guo)長。

　　脈沖電(dian)(dian)(dian)(dian)(dian)流充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)在充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)過程(cheng)中(zhong)是斷(duan)斷(duan)續(xu)續(xu)的(de)(de)(de)。采用(yong)這(zhe)種充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)方(fang)式(shi)可以(yi)提(ti)高電(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)接受能力、消除電(dian)(dian)(dian)(dian)(dian)極化作用(yong)、縮短充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)間(jian)、增大放電(dian)(dian)(dian)(dian)(dian)容量、減少電(dian)(dian)(dian)(dian)(dian)池發熱和提(ti)高充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)效率。但是目前的(de)(de)(de)脈沖充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)的(de)(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)脈沖寬度和間(jian)歇時(shi)間(jian)都是固定的(de)(de)(de)，不(bu)能根據充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)狀態改變充(chong)(chong)、放電(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)時(shi)間(jian)參數以(yi)及適應(ying)快速充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)要求(qiu)，因此充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)效果受到了限制。

　　結(jie)合以上兩點，本設計采用了一種(zhong)更(geng)好(hao)、更(geng)優化的充電方式，即(ji)恒流(liu)限壓與(yu)實時監測的智能控制充電方式。該(gai)充電方式對主回路開(kai)關電(dian)源(yuan)進行數字控制輸出(chu)電(dian)壓和(he)電(dian)流。

　　鎳鎘電池充電特(te)性曲線(xian)如圖1所示。當恒定電(dian)(dian)流充(chong)入(ru)剛放完電(dian)(dian)的(de)電(dian)(dian)池時(shi)，由于(yu)電(dian)(dian)池內阻(zu)產(chan)生(sheng)壓降，電(dian)(dian)池電(dian)(dian)壓很快上升至A點。此后，電(dian)池開(kai)始接受電(dian)荷，電(dian)池電(dian)壓以較低的速率持續上(shang)升(sheng)。在(zai)AB之間，電化學反(fan)應以(yi)一定的速率產生氧(yang)(yang)氣(qi)(qi)，同(tong)(tong)時氧(yang)(yang)氣(qi)(qi)也以(yi)同(tong)(tong)樣的速率與氫氣(qi)(qi)化臺(tai)，使電池內部(bu)的溫度和氣(qi)(qi)體壓(ya)力都很低。經過(guo)一定時間至(zhi)C點，電(dian)(dian)解(jie)液中開(kai)始(shi)產生氣泡，這些氣泡聚集(ji)在極(ji)(ji)板表面，使極(ji)(ji)板的(de)有效面積減小，電(dian)(dian)池的(de)內阻抗(kang)增加。電(dian)(dian)池電(dian)(dian)壓開(kai)始(shi)較快上(shang)升。這是接近充足電(dian)(dian)的(de)信號。

　　充足(zu)電(dian)(dian)(dian)后，充入電(dian)(dian)(dian)池(chi)的(de)(de)(de)(de)電(dian)(dian)(dian)流不是(shi)轉換為電(dian)(dian)(dian)池(chi)的(de)(de)(de)(de)儲能，而是(shi)在正極板上產生(sheng)(sheng)氧(yang)(yang)氣超(chao)電(dian)(dian)(dian)位。氧(yang)(yang)氣是(shi)由氫(qing)氧(yang)(yang)化(hua)(hua)鉀(jia)和水組成的(de)(de)(de)(de)電(dian)(dian)(dian)解(jie)(jie)液(ye)電(dian)(dian)(dian)解(jie)(jie)而產生(sheng)(sheng)的(de)(de)(de)(de)，不是(shi)由氫(qing)氧(yang)(yang)化(hua)(hua)鎘(ge)還(huan)原為鎘(ge)而產生(sheng)(sheng)的(de)(de)(de)(de)。由于從大量(liang)的(de)(de)(de)(de)氫(qing)氧(yang)(yang)離子中比從很少的(de)(de)(de)(de)氫(qing)氧(yang)(yang)化(hua)(hua)鎘(ge)中更(geng)容易分解(jie)(jie)出氧(yang)(yang)氣，所以電(dian)(dian)(dian)池(chi)內的(de)(de)(de)(de)溫度(du)急劇上升，使得電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)下降。因(yin)此電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)曲線出現峰(feng)值D點。電(dian)解液中，氧氣的產(chan)生和復合是放熱反(fan)應(ying)，電(dian)池過充電(dian)即E點，不停地產生(sheng)氧氣，從而使電(dian)池內的(de)溫(wen)度和壓(ya)力升高。

　　
       3 硬件電路
   
       該智(zhi)能充電(dian)器(qi)采(cai)用單片機(ji)AT89C2051進行控制，使(shi)用了開關(guan)電源及A／D、D/A等(deng)技(ji)術。實現了鎳鎘電池(chi)的(de)智能充電。其硬件電路如圖2所示，整個電(dian)路分為開(kai)關電(dian)源部(bu)分和以單片機為主(zhu)的控制電(dian)路部(bu)分。

　　
       此開(kai)關(guan)電源屬于(yu)復合式開(kai)關(guan)電源，采用TL431的精(jing)密(mi)基準(zhun)和PC817組(zu)成反饋電路。整個工作過程：交流(liu)輸(shu)入經濾波、整流(liu)后成為(wei)直流(liu)高壓，再由功率開關管斬波、高(gao)頻變壓器降壓后(hou)(hou)得到(dao)高頻矩形波電(dian)壓，最后(hou)(hou)經過輸出(chu)整流濾(lv)波器，獲得所需要的直(zhi)流輸出電壓。此開關電源達(da)到了：交流輸入電壓范圍為90～270V，能同(tong)時輸(shu)出(chu)+5V(作為控(kong)制部分電源)及4.4~11.3V(主回路)的(de)電(dian)(dian)壓(ya)，輸出電(dian)(dian)流為1A。其電路如圖3所(suo)示。

       
       控制電(dian)路(lu)部分主要由AT89C2051、ADC TLC0832、運放LM358及數字(zi)電(dian)位器(qi)X9C102、分壓電阻、電流采樣電阻組成。單片(pian)機對(dui)正在(zai)充電(dian)的電(dian)池進行(xing)實時電(dian)壓、電(dian)流取樣，經A／D轉換(huan)后輸(shu)入單片機(ji)。單片機(ji)根(gen)據電(dian)(dian)池不(bu)同(tong)的充(chong)電(dian)(dian)狀(zhuang)態采取不(bu)同(tong)的充(chong)電(dian)(dian)算法，通過數字電位(wei)器(qi)對(dui)開關電(dian)源的輸出電(dian)壓進行控制，通過改變電池(chi)組(zu)端電壓來達到控制(zhi)充電過程(cheng)的目(mu)的。

　　電(dian)(dian)(dian)路(lu)接上蓄電(dian)(dian)(dian)池后(hou)，充(chong)電(dian)(dian)(dian)過程(cheng)開(kai)始，當(dang)檢(jian)測到(dao)電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)在正常(chang)范圍內時，充(chong)電(dian)(dian)(dian)器軟啟動，充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)、電(dian)(dian)(dian)流(liu)逐漸增加到(dao)額定恒(heng)定充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)值，進(jin)行(xing)恒(heng)流(liu)充(chong)電(dian)(dian)(dian)，“正(zheng)充(chong)電”LED燈閃爍，同(tong)時開始計時。此后不(bu)斷檢測電池電壓，當電池電壓大于或達到規定(ding)的最(zui)大值(該電池(chi)規定的最(zui)大(da)值為10．5V)或(huo)充電時間(jian)等于5小(xiao)(xiao)時后，單片機發出指令(ling)，減小(xiao)(xiao)數控(kong)輸出值大小(xiao)(xiao)，使充電電流(liu)減小(xiao)(xiao)，轉為涓流(liu)充電(0．1A)，“已充滿”LED指示(shi)燈亮(liang)。這(zhe)樣就(jiu)避免了因電池(chi)(chi)溫升過快或嚴重極化，影響充(chong)電質(zhi)量、降低蓄電池(chi)(chi)的(de)使用壽命甚至產生事(shi)故，從(cong)而快速、安(an)全、高質(zhi)量地完成(cheng)充(chong)電過程。

　　4 軟件(jian)智能(neng)控(kong)制
   
       在程序的(de)初(chu)始階(jie)段首先應對單片機進行(xing)初(chu)始化，然后判(pan)斷(duan)電(dian)池是否連接(jie)正確，根據電(dian)池電(dian)壓判(pan)斷(duan)應該進入哪一個充電(dian)階(jie)段，即恒(heng)

流(liu)或者涓流(liu)充電(dian)方式(shi)。恒流(liu)方式(shi)：不斷檢測(ce)流(liu)過電(dian)池的電(dian)流(liu)是否達到恒定電(dian)流(liu)(1A)，如果小于lA則抬高電池(chi)兩(liang)端的電壓使(shi)之(zhi)達到lA(在電池(chi)兩端電壓(ya)小于電池(chi)的(de)最大充電電壓(ya)10．5V的前提下)。涓流(liu)方式：在電(dian)池兩端電(dian)壓達到(dao)最大值(zhi)后(hou)進入涓流(liu)充電(dian)模式。程序結構圖如圖4所示。

      本文(wen)提出(chu)一種恒流限(xian)壓、智能控(kong)制的(de)(de)(de)充電(dian)(dian)(dian)(dian)方案，能很好地解決鎳鎘蓄電(dian)(dian)(dian)(dian)池組在(zai)充電(dian)(dian)(dian)(dian)過(guo)程中(zhong)(zhong)存(cun)在(zai)的(de)(de)(de)過(guo)充電(dian)(dian)(dian)(dian)、充電(dian)(dian)(dian)(dian)不(bu)(bu)(bu)足(zu)、發熱等問題(ti)。該充電(dian)(dian)(dian)(dian)器(qi)已批量生(sheng)產并投入使(shi)用(yong)，效果令人滿意。同時，在(zai)已有的(de)(de)(de)基(ji)礎上針對不(bu)(bu)(bu)同種類(lei)(lei)的(de)(de)(de)電(dian)(dian)(dian)(dian)池，只要根據不(bu)(bu)(bu)同電(dian)(dian)(dian)(dian)池的(de)(de)(de)最(zui)佳充電(dian)(dian)(dian)(dian)曲(qu)線對控(kong)制器(qi)中(zhong)(zhong)的(de)(de)(de)程序進(jin)行相應的(de)(de)(de)調(diao)整，就(jiu)能對不(bu)(bu)(bu)同類(lei)(lei)型的(de)(de)(de)電(dian)(dian)(dian)(dian)池進(jin)行充電(dian)(dian)(dian)(dian)。