6.3　Recharging Efficiency

Text（课文）

Like all physical transformations，charge and discharge do not have an efficiency of 100%because the chemical processes are not perfectly reversible and the battery has certain internal impedance which dissipates part of the energy in heat.We retain two efficiency coefficients:

The electric efficiency of the battery

The electric efficiency of the battery，which is given by the relationship between the energy actually provided by the battery during the discharge and the electric energy provided by the charger to reach the initial state of the battery.This energy，measured in Watt is given by the integral of the“voltage by current”multiplication at the battery terminals at the time of the charge and the discharge.This value is lower than the faradic battery efficiency，and can pass from 70% for certain lead-acid batteries to 95% for new-technology batteries used under optimal conditions.

The efficiency of the battery-plus-charger system

It is obtained by measuring the relationship between the total energy provided by the battery at the time of the recharging and the electric network energy provided to the charger to reach the initial charge state of the battery.This coefficient thus takes account of all off the losses of the“battery＋charger”system.The efficiency of the charger is very dependent on the employed technology and their charge operating process.It is thus a culmination of all the efficiencies.

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.Like all physical transformations，charge and discharge do not have an efficiency of 100%because the chemical processes are not perfectly reversible and the battery has certain internal impedance which dissipates part of the energy in heat.与所有的自然现象一样，充放电过程不能达到100%的效率。因为该化学过程不是完全可逆的，并且电池具有内部阻抗会耗散损失一部分的能量。

Exercises（练习）

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

（1）The efficiency of the charger is very dependent on the employed technology and their charge operating process.

（2）electric network energy

（3）initial state

Reading material（阅读材料）

The faradic efficiency，which is equal to the relationship between the number of coulombs（the integral of the current）provided by the battery during the discharge and the number of coulombs necessary at the time of the recharge to reach the initial charge state of the battery before the beginning of the discharge.It is the coefficient generally indicated by manufacturers.This is close to 1 for new batteries（nickel-metal hydrive，lithium ion）.It is a little lower for lead-acid batteries and open nickel-cadmium batteries，which require a longer overload phase.