磷酸鐵鋰電池的直流內阻是評價電池性能的重要指標之一。內阻的測試包括交流內阻與直流內阻。對于磷酸鐵鋰電池單體，一般以交流內阻來進行評價，即通常稱為歐姆內阻。但對于大型磷酸鐵鋰電池組應用，如電動車用電源系統來說，由于測試設備等方面的限制，不能或不方便來直接進行交流內阻的測試，一般通過直流內阻來評價電池組的特性。在實際應用中，也多用直流內阻來評價電池的健康度，進行壽命預測，以及進行系統SOC、輸出輸入能力等(deng)(deng)的(de)估計(ji)。在生產中，可(ke)以用來(lai)檢測故障電池(chi)如微短路等(deng)(deng)現象。

磷酸鐵(tie)鋰電(dian)(dian)(dian)(dian)池(chi)直(zhi)(zhi)流(liu)(liu)(liu)內(nei)阻的(de)(de)(de)(de)測試(shi)原理是通(tong)過對(dui)電(dian)(dian)(dian)(dian)池(chi)或(huo)電(dian)(dian)(dian)(dian)池(chi)組施加(jia)較(jiao)(jiao)大的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)（充(chong)電(dian)(dian)(dian)(dian)或(huo)放電(dian)(dian)(dian)(dian)），持續較(jiao)(jiao)短時(shi)間，在電(dian)(dian)(dian)(dian)池(chi)內(nei)部還(huan)沒有達到完全(quan)極(ji)化的(de)(de)(de)(de)情況下，根據施加(jia)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)前后電(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)壓變化和(he)施加(jia)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，計算電(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)(de)直(zhi)(zhi)流(liu)(liu)(liu)內(nei)阻。測試(shi)直(zhi)(zhi)流(liu)(liu)(liu)內(nei)阻必須選擇(ze)好四個參數：電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)（或(huo)采用的(de)(de)(de)(de)倍率）、脈(mo)沖(chong)時(shi)間、荷電(dian)(dian)(dian)(dian)狀態（SOC）、測試(shi)環(huan)境溫度(du)。這些參數的(de)(de)(de)(de)變化對(dui)直(zhi)(zhi)流(liu)(liu)(liu)內(nei)阻有較(jiao)(jiao)大的(de)(de)(de)(de)影響。

直流內(nei)阻(zu)不僅包(bao)括了電(dian)池(chi)組(zu)的(de)歐(ou)姆(mu)內(nei)阻(zu)部分，還部分包(bao)括了電(dian)池(chi)組(zu)的(de)一些(xie)極化電(dian)阻(zu)。

而(er)電(dian)(dian)(dian)池的(de)(de)極化受電(dian)(dian)(dian)流(liu)、時間等影響比較大。目前常用的(de)(de)磷酸鐵鋰電(dian)(dian)(dian)池直流(liu)內阻(zu)測試(shi)方法(fa)有以下三個：（1）美國《FreedomCAR電(dian)(dian)(dian)池測試(shi)手(shou)冊》中的(de)(de)HPPC測試(shi)方法(fa)：測試(shi)持續(xu)時間為10s，施加的(de)(de)放電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)為5C或更高，充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)為放電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)的(de)(de)0.75。具體電(dian)(dian)(dian)流(liu)的(de)(de)選擇(ze)根據電(dian)(dian)(dian)池的(de)(de)特(te)性來制定(ding)。

（2）日本JEVSD7132003的測試方法，原來主要針對Ni/MI電池，后也應用于鋰離子電池，首(shou)先建立0~100%SOC下電(dian)(dian)(dian)(dian)池的電(dian)(dian)(dian)(dian)流一電(dian)(dian)(dian)(dian)壓特性(xing)(xing)曲線，分別以1C、2C、5C、10C的電(dian)(dian)(dian)(dian)流對設(she)定SOC下的電(dian)(dian)(dian)(dian)池進行(xing)交替充電(dian)(dian)(dian)(dian)或放電(dian)(dian)(dian)(dian)，充電(dian)(dian)(dian)(dian)或放電(dian)(dian)(dian)(dian)時間(jian)分別為(wei)(wei)(wei)10s，計算電(dian)(dian)(dian)(dian)池的直流內阻。（3）我國“863”計劃(hua)電(dian)(dian)(dian)(dian)動(dong)汽車重大專項《HEV用高功率鋰離子動(dong)力蓄電(dian)(dian)(dian)(dian)池性(xing)(xing)能測(ce)試規范》中提出(chu)的測(ce)試方法(fa)，測(ce)試持(chi)續時間(jian)為(wei)(wei)(wei)5s，充電(dian)(dian)(dian)(dian)測(ce)試電(dian)(dian)(dian)(dian)流為(wei)(wei)(wei)3C，放電(dian)(dian)(dian)(dian)測(ce)試電(dian)(dian)(dian)(dian)流為(wei)(wei)(wei)9C。

JEVS法(fa)、HPPC法(fa)兩(liang)(liang)種(zhong)測(ce)(ce)(ce)試(shi)(shi)方(fang)法(fa)各有特點，JEVS法(fa)采(cai)用(yong)0~10C“系列”電(dian)(dian)(dian)流(liu)(liu)可(ke)以避免采(cai)用(yong)單一電(dian)(dian)(dian)流(liu)(liu)產(chan)生的(de)(de)(de)(de)結(jie)果偏差，其假定(ding)(ding)電(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)(de)(de)內(nei)阻(zu)(zu)主要成(cheng)分(fen)是近似恒定(ding)(ding)的(de)(de)(de)(de)歐(ou)姆阻(zu)(zu)抗(kang)，因此在放(fang)電(dian)(dian)(dian)倍(bei)(bei)(bei)率(lv)較(jiao)(jiao)低(di)(di)情(qing)況下可(ke)靠性(xing)(xing)較(jiao)(jiao)高(gao)(gao)(gao)。實(shi)際上在電(dian)(dian)(dian)池(chi)(chi)(chi)高(gao)(gao)(gao)倍(bei)(bei)(bei)率(lv)充(chong)放(fang)電(dian)(dian)(dian)時(shi)(shi)，整個電(dian)(dian)(dian)池(chi)(chi)(chi)反(fan)應(ying)的(de)(de)(de)(de)速率(lv)控制(zhi)(zhi)步(bu)驟由小倍(bei)(bei)(bei)率(lv)下的(de)(de)(de)(de)電(dian)(dian)(dian)荷轉移過(guo)程控制(zhi)(zhi)變為傳質過(guo)程控制(zhi)(zhi)，電(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)(de)(de)阻(zu)(zu)抗(kang)構成(cheng)中(zhong)(zhong)不(bu)(bu)僅有電(dian)(dian)(dian)池(chi)(chi)(chi)本體歐(ou)姆阻(zu)(zu)抗(kang)，還有極(ji)化(hua)反(fan)應(ying)阻(zu)(zu)抗(kang)等(deng)，并且隨電(dian)(dian)(dian)流(liu)(liu)和(he)脈沖時(shi)(shi)間發生變化(hua)。HPPC法(fa)同時(shi)(shi)采(cai)用(yong)中(zhong)(zhong)低(di)(di)倍(bei)(bei)(bei)率(lv)及(ji)高(gao)(gao)(gao)倍(bei)(bei)(bei)率(lv)兩(liang)(liang)個電(dian)(dian)(dian)流(liu)(liu)段測(ce)(ce)(ce)試(shi)(shi)電(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)(de)(de)功率(lv)能(neng)力(li)，兼(jian)顧了(le)電(dian)(dian)(dian)池(chi)(chi)(chi)在中(zhong)(zhong)低(di)(di)兩(liang)(liang)種(zhong)倍(bei)(bei)(bei)率(lv)及(ji)高(gao)(gao)(gao)倍(bei)(bei)(bei)率(lv)充(chong)電(dian)(dian)(dian)或(huo)放(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)下不(bu)(bu)同的(de)(de)(de)(de)電(dian)(dian)(dian)壓響應(ying)特性(xing)(xing)，但(dan)采(cai)用(yong)某(mou)一電(dian)(dian)(dian)流(liu)(liu)（5C、15C）分(fen)別代(dai)表中(zhong)(zhong)低(di)(di)倍(bei)(bei)(bei)率(lv)或(huo)高(gao)(gao)(gao)倍(bei)(bei)(bei)率(lv)電(dian)(dian)(dian)池(chi)(chi)(chi)功率(lv)能(neng)力(li)的(de)(de)(de)(de)方(fang)法(fa)缺乏全(quan)面(mian)性(xing)(xing)，不(bu)(bu)同電(dian)(dian)(dian)池(chi)(chi)(chi)某(mou)一電(dian)(dian)(dian)流(liu)(liu)（5C、15C）下的(de)(de)(de)(de)電(dian)(dian)(dian)壓響應(ying)不(bu)(bu)同，造(zao)成(cheng)了(le)測(ce)(ce)(ce)試(shi)(shi)結(jie)果的(de)(de)(de)(de)片面(mian)和(he)偏差。“863“測(ce)(ce)(ce)試(shi)(shi)規(gui)范中(zhong)(zhong)采(cai)用(yong)一種(zhong)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)和(he)放(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)，并且兩(liang)(liang)者差距比(bi)較(jiao)(jiao)大(da)，具有一定(ding)(ding)的(de)(de)(de)(de)片面(mian)性(xing)(xing)。每種(zhong)測(ce)(ce)(ce)試(shi)(shi)方(fang)法(fa)均可(ke)以作為一個基準方(fang)法(fa)來測(ce)(ce)(ce)試(shi)(shi)，對(dui)不(bu)(bu)同的(de)(de)(de)(de)電(dian)(dian)(dian)源系統進(jin)行比(bi)較(jiao)(jiao)。但(dan)每種(zhong)電(dian)(dian)(dian)池(chi)(chi)(chi)均有一定(ding)(ding)的(de)(de)(de)(de)適應(ying)性(xing)(xing)，其受測(ce)(ce)(ce)試(shi)(shi)電(dian)(dian)(dian)流(liu)(liu)和(he)時(shi)(shi)間的(de)(de)(de)(de)不(bu)(bu)同，內(nei)阻(zu)(zu)的(de)(de)(de)(de)變化(hua)規(gui)律也會(hui)發生變化(hua)。