蓄電池作為能量的轉存裝(zhuang)置(zhi)或(huo)備(bei)用電源被廣泛地(di)應用于各種(zhong)自動化設備(bei)中。使用普通的充電器對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機所使用(yong)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(chi)的(de)發展(zhan)及特點
    
       1899年，Waldmar Jungner首(shou)先在開口型鎳鎘蓄電弛(chi)中使用了鎳極板，同(tong)時，Thomos Edison發明了用于電(dian)動車的鎳鐵電(dian)池。但是．由(you)于當時(shi)這些堿性蓄電池的(de)極板(ban)材料比其他(ta)蓄電池的(de)材料貴得多，其實(shi)際應(ying)用(yong)受(shou)到了極大的(de)限制。直到1932年(nian)，鎳鎘電池經歷了最重(zhong)要的(de)改進(jin)：科(ke)學家在鎳電池中(zhong)開始使(shi)用活性物質。1947年(nian)，密封型(xing)鐮鎘電

池研制(zhi)成功(gong)。

　　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(ge)電池的(de)充(chong)電方式及充(chong)電特性曲線
   
       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以分為連續電(dian)(dian)流充電(dian)(dian)和脈(mo)沖電(dian)(dian)流充電(dian)(dian)兩大類(lei)。

　　連(lian)續(xu)電(dian)(dian)(dian)(dian)(dian)流(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)因放(fang)電(dian)(dian)(dian)(dian)(dian)容量(liang)受到電(dian)(dian)(dian)(dian)(dian)池接受能(neng)力的限制和受到在充(chong)電(dian)(dian)(dian)(dian)(dian)過(guo)程(cheng)中(zhong)電(dian)(dian)(dian)(dian)(dian)池極(ji)化所產生(sheng)氣體的阻力，使得在大電(dian)(dian)(dian)(dian)(dian)流(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)的情況下，電(dian)(dian)(dian)(dian)(dian)池放(fang)電(dian)(dian)(dian)(dian)(dian)容量(liang)下降和電(dian)(dian)(dian)(dian)(dian)池發熱；若(ruo)用(yong)小電(dian)(dian)(dian)(dian)(dian)流(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)，雖可(ke)克服這個(ge)缺點，但充(chong)電(dian)(dian)(dian)(dian)(dian)時間(jian)過(guo)長。

　　脈沖電(dian)(dian)(dian)(dian)流充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)在充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)過程(cheng)中是斷斷續續的(de)(de)。采(cai)用這種充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)方式可(ke)以(yi)提(ti)高電(dian)(dian)(dian)(dian)池的(de)(de)接(jie)受(shou)能力(li)、消除電(dian)(dian)(dian)(dian)極(ji)化作用、縮短充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時間(jian)(jian)(jian)、增大放電(dian)(dian)(dian)(dian)容量、減少電(dian)(dian)(dian)(dian)池發熱和提(ti)高充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)效率。但(dan)是目前的(de)(de)脈沖充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器的(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)脈沖寬度和間(jian)(jian)(jian)歇(xie)時間(jian)(jian)(jian)都是固定的(de)(de)，不能根據充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)狀態改變充(chong)(chong)(chong)、放電(dian)(dian)(dian)(dian)的(de)(de)時間(jian)(jian)(jian)參(can)數以(yi)及適應快速(su)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)的(de)(de)要求(qiu)，因此充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)效果受(shou)到(dao)了限制。

　　結合以上兩(liang)點，本設計采用了一種更好、更優化的充電方式(shi)，即恒流(liu)限壓與實(shi)時監測的智能控(kong)制充電方式(shi)。該充電方式(shi)對主回路開關電源(yuan)進行數字(zi)控(kong)制輸出電壓(ya)和(he)電流。

　　鎳鎘(ge)電池充電特性曲線(xian)如(ru)圖1所示。當恒定電(dian)流充入剛放完電(dian)的電(dian)池時，由于電(dian)池內阻產生壓降(jiang)，電(dian)池電(dian)壓很快上升至A點。此后，電池(chi)開始接受電荷，電池(chi)電壓以較(jiao)低的速率(lv)持續上升。在AB之間，電(dian)(dian)化學(xue)反應(ying)以一定(ding)的(de)速(su)率(lv)產生氧氣(qi)(qi)，同時氧氣(qi)(qi)也以同樣(yang)的(de)速(su)率(lv)與氫氣(qi)(qi)化臺，使電(dian)(dian)池內部(bu)的(de)溫(wen)度和氣(qi)(qi)體壓力都很低。經(jing)過一定(ding)時間至C點，電解液中(zhong)開始產生氣泡，這些氣泡聚集在極(ji)板(ban)表面(mian)，使極(ji)板(ban)的(de)有效面(mian)積減(jian)小，電池(chi)的(de)內阻抗增加(jia)。電池(chi)電壓開始較快上(shang)升(sheng)。這是(shi)接近充足電的(de)信(xin)號。

　　充(chong)足電(dian)(dian)(dian)(dian)后(hou)，充(chong)入電(dian)(dian)(dian)(dian)池的(de)(de)電(dian)(dian)(dian)(dian)流(liu)不是轉換為電(dian)(dian)(dian)(dian)池的(de)(de)儲(chu)能，而(er)是在正極板(ban)上產(chan)生氧(yang)(yang)氣(qi)超電(dian)(dian)(dian)(dian)位。氧(yang)(yang)氣(qi)是由氫(qing)氧(yang)(yang)化鉀和水組成的(de)(de)電(dian)(dian)(dian)(dian)解(jie)液電(dian)(dian)(dian)(dian)解(jie)而(er)產(chan)生的(de)(de)，不是由氫(qing)氧(yang)(yang)化鎘還原為鎘而(er)產(chan)生的(de)(de)。由于從大量的(de)(de)氫(qing)氧(yang)(yang)離子中比從很少的(de)(de)氫(qing)氧(yang)(yang)化鎘中更容易分解(jie)出(chu)氧(yang)(yang)氣(qi)，所以(yi)電(dian)(dian)(dian)(dian)池內的(de)(de)溫度急劇上升，使得(de)電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓(ya)下降(jiang)。因此(ci)電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓(ya)曲(qu)線出(chu)現(xian)峰(feng)值(zhi)D點。電解液(ye)中，氧氣的產生(sheng)和復合(he)是放熱(re)反應(ying)，電池過充電即E點，不停地產生(sheng)氧氣，從而使電(dian)池內的溫(wen)度和壓力(li)升高(gao)。

　　
       3 硬(ying)件電路
   
       該智能(neng)充(chong)電器采用(yong)單片機AT89C2051進行控制，使用了開關電源及A／D、D/A等技術。實現了(le)鎳鎘電(dian)(dian)(dian)池的智能充電(dian)(dian)(dian)。其(qi)硬件電(dian)(dian)(dian)路如圖2所示，整個電路(lu)分(fen)為開關電源部分(fen)和以單片機為主的控制電路(lu)部分(fen)。

　　
       此(ci)開關電(dian)源(yuan)屬于復合式開關電(dian)源(yuan)，采用TL431的精密(mi)基準和(he)PC817組成反饋電路(lu)。整(zheng)個工作過程：交流(liu)輸入經濾波(bo)、整(zheng)流(liu)后成為直流(liu)高壓，再由功(gong)率開(kai)關(guan)管(guan)斬(zhan)波、高頻變壓器降壓后得到高頻矩形波電(dian)壓，最后經過輸出整流(liu)濾波器，獲得所需要的(de)直流(liu)輸出電(dian)壓(ya)。此開關電(dian)源達到了：交流(liu)輸入電(dian)壓(ya)范圍為90～270V，能同(tong)時輸出+5V(作為控制部分電(dian)源)及4.4~11.3V(主回路(lu))的電壓，輸出電流為1A。其電路如圖3所示。

       
       控制電路部分主要由(you)AT89C2051、ADC TLC0832、運放LM358及數(shu)字電位器(qi)X9C102、分(fen)壓(ya)電阻、電流采樣電阻組(zu)成。單片機對正(zheng)在充電的電池進行(xing)實(shi)時電壓、電流取樣，經A／D轉換后(hou)輸入單(dan)片機。單(dan)片機根據電池不同的(de)充電狀態采取不同的(de)充電算法(fa)，通(tong)過數字電位器對開關電(dian)(dian)源的輸出電(dian)(dian)壓進行(xing)控制(zhi)，通過改變電池組(zu)端電壓來(lai)達到(dao)控制充(chong)電過程(cheng)的(de)目的(de)。

　　電(dian)(dian)路(lu)接(jie)上(shang)蓄電(dian)(dian)池(chi)(chi)后(hou)，充(chong)電(dian)(dian)過程開(kai)始，當檢測到電(dian)(dian)池(chi)(chi)電(dian)(dian)壓在(zai)正(zheng)常范圍(wei)內時(shi)，充(chong)電(dian)(dian)器軟啟動，充(chong)電(dian)(dian)電(dian)(dian)壓、電(dian)(dian)流(liu)逐漸(jian)增加(jia)到額定恒定充(chong)電(dian)(dian)電(dian)(dian)流(liu)值，進(jin)行(xing)恒流(liu)充(chong)電(dian)(dian)，“正充(chong)電(dian)”LED燈閃爍(shuo)，同時(shi)開始計時(shi)。此后不(bu)斷檢測(ce)電(dian)池電(dian)壓，當電(dian)池電(dian)壓大于或達到(dao)規定的最大值(該電(dian)池(chi)規定的最大值為10．5V)或充電時(shi)間(jian)等于5小(xiao)(xiao)(xiao)時后，單片(pian)機發出指令，減小(xiao)(xiao)(xiao)數控輸出值大小(xiao)(xiao)(xiao)，使充電電流(liu)(liu)減小(xiao)(xiao)(xiao)，轉為(wei)涓流(liu)(liu)充電(0．1A)，“已充滿”LED指示燈亮。這樣就避(bi)免了(le)因電(dian)(dian)池溫升過快(kuai)或嚴重極化，影響充電(dian)(dian)質(zhi)量、降低蓄電(dian)(dian)池的(de)使用壽命(ming)甚至產生(sheng)事(shi)故，從而快(kuai)速(su)、安全、高質(zhi)量地完成充電(dian)(dian)過程。

　　4 軟件智(zhi)能控制
   
       在程序的初(chu)始(shi)階(jie)段首(shou)先應對單片機進行初(chu)始(shi)化，然后判斷電池是否連接(jie)正確，根據電池電壓(ya)判斷應該(gai)進入哪(na)一個充電階(jie)段，即恒

流(liu)(liu)或(huo)者(zhe)涓流(liu)(liu)充(chong)電(dian)(dian)方式。恒(heng)流(liu)(liu)方式：不斷檢測流(liu)(liu)過電(dian)(dian)池的電(dian)(dian)流(liu)(liu)是否達到恒(heng)定(ding)電(dian)(dian)流(liu)(liu)(1A)，如果小于(yu)lA則抬高電池(chi)兩端(duan)的電壓使(shi)之(zhi)達到(dao)lA(在電(dian)池兩端電(dian)壓小于電(dian)池的最大充(chong)電(dian)電(dian)壓10．5V的前提下)。涓流方(fang)式：在電(dian)池兩端(duan)電(dian)壓(ya)達(da)到(dao)最大(da)值后進(jin)入涓流充電(dian)模式。程序結構圖如(ru)圖4所(suo)示。

      本文(wen)提(ti)出(chu)一種恒流限壓、智(zhi)能控(kong)制的充(chong)電(dian)方(fang)案，能很好地(di)解(jie)決鎳鎘(ge)蓄(xu)電(dian)池組在充(chong)電(dian)過程中存在的過充(chong)電(dian)、充(chong)電(dian)不(bu)足、發熱等問題。該充(chong)電(dian)器(qi)已批(pi)量生(sheng)產并投入使用，效果令(ling)人滿意(yi)。同時，在已有(you)的基(ji)礎上針對不(bu)同種類的電(dian)池，只要根據不(bu)同電(dian)池的最佳充(chong)電(dian)曲線(xian)對控(kong)制器(qi)中的程序進行相應(ying)的調整，就能對不(bu)同類型(xing)的電(dian)池進行充(chong)電(dian)。