3.1　Electrochemical Batteries

Text（课文）

Electrochemical batteries，more commonly referred to as“batteries，”are electrochemical devices that convert electrical energy into potential chemical energy during charging，and convert chemical energy into electric energy during discharging.A battery is composed of several cells stacked together.A cell is an independent and complete unit that possesses all the electrochemical properties.Basically，a battery cell consists of three primary elements:two electrodes（positive and negative），immersed into electrolyte as shown in Figure 3.1.

Battery manufacturers usually specify the battery with coulometric capacity（ampere-hours），which is defined as the number of ampere-hours gained when discharging the battery from a fully charged state until the terminal voltage drops to its cut-off voltage，as shown in Figure 3.2.It should be noted that the same battery usually has a different number of ampere-hours at different discharging current rates.Generally，the capacity will become smaller with a large discharge current rate，as shown in Figure 3.3.Battery manufacturers usually specify a battery with a number of amperehours along with a current rate.For example，a battery labeled as 100（A·h）at C/5 rate has a 100（A·h）capacity at a 5h discharge rate（discharging current＝100/5＝20 A）.

Figure 3.1　A typical electrochemical battery cell

Figure 3.2　Cut-off voltage of a typical battery

Figure 3.3　Discharge characteristics of a lead-acid battery

New words and expressions（单词和短语）

1.New words（单词）

2.Expressions（短语）

Notes to the text（难点解析）

★1.Generally，the capacity will become smaller with a large discharge current rate.一般，在高电流放电率的情况下，容量将变得较小。

★2.It should be noted that the same battery usually has a different number of ampere-hours at different discharging current rates.应该注意，同样的蓄电池在不同的电流放电率下，通常具有不同的安时数。

Exercises（练习）

◆1.Translate the following passages（expressions）into Chinese（英译汉）

（1）A cell is an independent and complete unit that possesses all the electrochemical properties.

（2）electrical energy

（3）chemical energy

◆2.Translate the following passages（expressions）into English（汉译英）

（1）终止电压

（2）电流放电率

（3）在充电时，它将电能变换为潜在的化学能。