WHAT?IS?THE?“MEMORY?EFFECT”??
Memory?Effect?affects?the?run?time?of?a?traditional?(NiCd)?Nickel?Cadmium?Rechargeable?Battery.?There?is?some?misconception?about?the?word?“memory”.?Memory?is?commonly?blamed?for?just?about?any?battery?failure?known?to?man.?The?word?”memory”?is?derived?from?“cyclic?memory”,?meaning?that?a?NiCd?battery?could?remember?how?much?discharge?was?required?on?previous?discharges?and?then?fail?to?regain?a?full?capacity?recharge.?Improvements?in?battery?technology?have?virtually?eliminated?this?phenomenon.?The?problem?with?the?modern?NiCd?battery?is?not?the?cyclic?memory?but?the?effects?of?large?crystalline?formation.?(When?we?refer?to?memory,?we?are?referring?to?the?formation?of?crystals.)?The?active?materials?(nickel?&?cadmium)?of?a?NiCd?battery?are?present?in?crystalline?form.?When?the?memory?Phenomenon?occurs,?these?crystals?grow,?forming?spike?or?tree-like?crystals?that?cause?the?NiCd?to?gradually?lose?performance?and?shut?off?early?.?In?advanced?stages,?these?crystals?may?puncture?the?separator,?causing?high?self-discharge?or?an?electrical?short.?Crystalline?formation?only?presents?a?problem?if?the?battery?is?repeatedly?recharged?without?a?periodic?full?discharge.?It?is?not?necessary?to?discharge?a?NiCd?before?each?charge.?A?full?discharge?to?one?volt?per?cell?once?a?month?is?sufficient?to?keep?the?crystal?formation?under?control.?Such?a?discharge/charge?cycle?is?commonly?referred?to?as?“exercise”.?
If?no?exercise?is?applied?for?several?months,?the?crystals?engrain?themselves,?making?it?more?difficult?to?dissolve.?In?such?a?case,?exercise?is?no?longer?effective?in?restoring?a?battery?and?“recondition”?is?required.?Recondition?is?a?slow,?deep?discharge?that?drains?the?cell?to?a?voltage?threshold?below?one?volt?must?be?discharged?to?at?least?0.6?volts?per?cell?to?dissolve?the?more?resistive?crystalline?build-up.?If?you?use?NiCd?batteries?you?should?purchase?a?charger?with?a?"conditioning"?function?to?neutralize?the?crystalline?build-up?problem.?
Not?all?NiCd?batteries?respond?well?to?recondition.?A?battery?that?has?been?in?service?for?over?a?year?and?had?not?been?exercised?regularly?may?have?a?capacity?reading?that?dropped?to?a?low?20%.?Even?with?repeated?recondition?cycles,?the?battery?may?not?improve?to?an?acceptable?capacity?
Nimh?Rechargeable?Batteries?have?almost?no?Memory?Effect.?Nimh?have?a?different?internal?chemistry?and?are?not?as?susceptible?to?the?same?“memory”?problems?as?NiCds.?In?fact?Nimh?batteries?can?and?should?be?charged?from?any?discharge?state.?This?is?a?major?advantage?of?Nimh?batteries?over?NiCd.
什么是“記憶效應(yīng)”？
記憶效應(yīng)影響了鎘鎳二次電池的放電時(shí)間。關(guān)于“記憶”一詞，存在一些誤解?！坝洃洝痹醋杂凇把h(huán)記憶”，它意味著鎘鎳電池能夠記住先前的放電量，不能再次充電到最大容量。電池技術(shù)的提高正逐漸消除這種現(xiàn)象。?現(xiàn)代鎘鎳電池的問題不在于循環(huán)記憶，而在于大量結(jié)晶結(jié)構(gòu)的影響。（當(dāng)我們提到記憶效應(yīng)的時(shí)候，我們將會提到結(jié)晶結(jié)構(gòu)。）鎘鎳電池里的活性物質(zhì)鎳和鎘都表現(xiàn)為晶體形式。當(dāng)記憶效應(yīng)發(fā)生時(shí)，晶體會增長，形成刺釘狀或樹狀結(jié)晶，這導(dǎo)致了鎳，鎘逐漸失去其原有功能。進(jìn)一步的反應(yīng)，這些晶體可能穿過分離器，導(dǎo)致高的自放電或者短路。如果電池在沒有完全周期性放電的情況下就被反復(fù)充電，就會導(dǎo)致結(jié)晶的形成。對于鎘鎳電池來講，每次充電前的放電是不必要的。每個(gè)月每個(gè)電芯完全放電到一伏足以保持水晶結(jié)構(gòu)在控制之下。像那樣的充放電循環(huán)通常被稱之為“exercise”。如果幾個(gè)月都不"exercise"，結(jié)晶將會再次集結(jié)，并且使之溶解將更加困難。?在那種情況下，"exercise"在重儲和恢復(fù)電池方面將不起作用。恢復(fù)是一種緩慢的，深度的放電過程，它放電使電芯達(dá)到一個(gè)電壓極限，一個(gè)電芯一定要由一伏的電壓至少放電至0.6伏以下，才能溶散更多的抗性晶體。?如果你使用鎘鎳電池，就應(yīng)該買一個(gè)帶有壓制形成結(jié)晶功能的充電器。?并非所有的鎘鎳電池都有一個(gè)好的恢復(fù)反應(yīng)。一個(gè)用了一年以上且不被經(jīng)常循環(huán)的電池，容量將下降到20%以下。這時(shí)即使多次重復(fù)恢復(fù)循環(huán)，電池也不會提高可接受的容量。鎳氫二次電池幾乎不受記憶效應(yīng)的影響。它的的內(nèi)部化學(xué)結(jié)構(gòu)使之不像鎘鎳電池一樣遭受記憶效應(yīng)的影響。事實(shí)上鎳氫電池在任何放電狀態(tài)下都可以進(jìn)行再充電。這是鎳氫電池優(yōu)于鎘鎳電池的一個(gè)主要的優(yōu)勢。