6.6.5　Temperature

In general，during charging the battery temperature increases to some extent，however，extra increase in temperature is a sign of overcharge.Using temperature sensors highly adds to the cost of the system.Nevertheless，for some chemistries such as Ni-MH，methods such as voltage drop is not recommended，since the voltage drop after full charge state is not significant to be relied on.In this case，temperature increase is a good indication of overcharge and can be used.

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.The other one is to avoid overcharging which is very dangerous especially in the case of high energy density Lithium-based battery packs.二是避免过充电，特别是在高能量密度的锂基电池的情况下，这是非常危险的。

★2.In addition，this technique is usually used with constant current techniques to avoid overheating damage to the battery.此外，该技术通常与恒流技术一起使用，这样可以避免电池过热。

Exercises（练习）

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

（1）However，extra increase in temperature is a sign of overcharge.

（2）In the last stages of charging，if constant voltage method is used，the current begins to decrease as the battery reaches fully charge state.

（3）open-circuit voltage

（4）regular charging

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

（1）充电的终止方式

（2）完全充电

（3）设置电池的充电时间可以作为其中的一种最简单的方法。

◆3.Directions:Answer the following questions briefly according to the text.

Why do we say it is very important to decide when to terminate the charging when the charging is in procedure？

Reading material（阅读材料）

Charging Algorithm

As mentioned before，lead-acid batteries have mature technology and infrastructure that already exist，but they still have poor life cycles in the order of 300-400 cycles.A lot of efforts have been put into research for increasing the life cycle of lead-acid batteries because of their advantages such as low cost and availability.This chemistry has a common charging algorithm which includes four different stages or three based on the application，as indicated in Figure 6.10.

Figure 6.10　Charging algorithm of a typical Lead-acid battery

In the first stage a predefined constant current is applied to the battery pack which charges the cells rapidly.In this stage the cell voltages increase gradually because of SOC increase.This stage is called“Bulk Charge”stage.The process is continued until a predefined maximum voltage is reached.These values are all recommended by the manufacturer in the datasheet.In the next stage called“Absorption Charge”stage，a constant voltage is applied to the battery pack.At this stage the current decreases gradually until it reaches a predefined C rate value and the cells are approximately charged but not equalized because of cell imbalance.At this stage a relatively higher voltage than constant voltage in absorption charge stage can be applied to the pack for some time to balance all the cells inside the pack.This stage is called“Equalization Charge”stage.The equalization can also be achieved with other techniques as mentioned before.After some prescribed time，the charger applies a lower constant voltage in order to keep the battery in a ready-to-use state.This is called“Float Charge”stage and depending on the application it can be considered or omitted.