4.2.4　Charge Management

Text（课文）

Proper charge and discharge of batteries can maintain healthy condition of the battery system.Consequently，improper charge and discharge can impact the battery life and capacity.

Batteries in the EV，HEV，and PHEV are charged in three scenarios:during plugin charge，during regenerative braking，and opportunity charge using engine power.The plugin charge is usually over an extended period of time at a lower charge rate.But the regenerative braking can happen at a much higher current level over very short time duration.

Plugin charge usually goes through five phases:

Diagnosis phase.When the car is plugged in，the BMS and charger will perform a series of testing to make sure the battery is capable of receiving charge.A small current，typically C/20 is injected to the battery.This phase can last a few minutes with the charging current gradually ramped up to the second phase.

Constant current charging phase.Once the battery passes the diagnosis，the battery is charged with constant current，usually at C/5 for regular charging，and C/2～2C for fast charging.

Constant voltage or reduced current charging phase.During the constant current charging phase，once one of the cells reaches the maximum voltage，the charging current is reduced.At this point，the battery can either be charged at a reduced current，or enter the constant voltage charging phase.

Balancing phase.However，depending on the imbalance of the battery cells，the constant voltage phase can take a long time.During this phase，the balancing circuit is activated for the cells that have reached the threshold.Once all battery cells reach the preset voltage threshold，the charge is stopped and the charger can be turned off.

Maintenance phase.Some batteries need a maintenance phase in which a very small amount of current is being injected to the battery to make up the leakage loss.Some battery packs have been designed to use this small current to keep the battery warm in cold weather（Figure 4.8）.

While the management of plugin charge is relatively straight forward，management of the charging of battery during regenerative braking can be very difficult.This is due to the fact that a large current is being injected to the battery to generate the desired braking torque，as well as the heat generated inside the battery due to battery internal resistance.

Figure 4.8　Plugin charge management

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 plugin charge is usually over an extended period of time at a lower charge rate.But the regenerative braking can happen at a much higher current level over very short time duration.插电式充电通常是在较长的时间内以较低的充电速率进行的。但可再生制动会在很短的时间内以很高的电流进行。

★2.At this point，the battery can either be charged at a reduced current，or enter the constant voltage charging phase.在这个点，电池组或者以减小的电流充电，或者进入恒电压充电阶段。

Exercises（练习）

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

（1）This is due to the fact that a large current is being injected to the battery to generate the desired braking torque，as well as the heat generated inside the battery due to battery internal resistance.

（2）constant current

（3）regenerative braking

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

（1）恒电压

（2）制动转矩

（3）由于单体组中单体之间的不平衡，恒电压阶段将持续很长时间。

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

Can you analyze five phases about plugin charge？