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锂电池充电模式及转换

电池充电知识很难找,本文是根据Android源码理解及对两款充电芯片资料摘要整理得到,方便理解充电电池的充电过程。锂电池充电过程跟镍氢电池充电过程不同(参考文末维基说明),镍氢电池只使用恒流充电,然后检测检测充满,而锂电池充电模式要复杂点,大概分为五种模式:预充电、全速充电、恒压充电、加满充电、充电完成,实际流程可能随芯片不同有所不同,尤其是一些Threshold阈值确定往往会有差别。

天缘非电池电源专业人士,如理解有误,欢迎指出为谢!本博客关于电池类总结还有:纽扣电池常见型号常见电池型号用途充电电池如何选购

一、充电模式理解

充电模式详细如下:

  • Pre-charge 预充电模式,也叫Pre-qualification Mode——一般电压低于2.8V左右时,会先进行预充电
  • CC-charge 恒流充电,也叫全速充电模式——此时电池电压迅速提高
  • CV-charge 恒压充电——转入恒压充电后,电池电压提高导致充电电流自然会逐渐减小
  • TOP-OFF 加满充电——当充电电流达到电池电量(mA)的5%或10%时,就会转入TOP-OFF充电模式,故也叫加满充电
  • Bat-Full 充电完成——当电池电压达到4.1V,4.2V,4.38V时,就会编程停止充电,但是当电池电压低于某个设定值时,又会返回全速充电模式继续充电,如此反复
  • Bat-Error 电池充电错误——这个是出错处理流程

二、充电模式英文

下面英文介绍为保证准确性,未做翻译,详细内容参考文末链接(英文介绍及下文插入摘自TI LP3910SQ-AN Datasheet 第40页/第41页)。

Pre-Qualification Mode

Lithium batteries cannot be subjected to a high current when the battery voltage is under a certain threshold, otherwise the longevity of the battery would be compromised. Below this threshold of VFULLRATE, which typically measures 2.85V, the charger circuit supplies a pre-qualification charge current. If the wall adapter is charging the battery, the charger circuit supplies a constant current of 10% of the programmed charge current. If the USB is charging the battery, the charger circuit supplies a constant 50 ma charge current. When the battery voltage reaches VFULL_RATE, the charger transitions from pre-qualification to full-rate charging. In Pre-qualification mode, the STAT2, STAT1, and STAT0 bits in the charger supervisory register are respectively low, low, high.

Full-Rate Charging Mode

The full-rate charge cycle is initiated following the successful completion of the pre-qualification mode. During Full-Rate charging, the battery voltage steadily increases while charged with a constant current (CC). The three charger status bits STAT2, STAT1 and STAT0 are respectively low, high, and low. The full-rate charge current is selected using the Charge Control Register, which defaults to 100 mA. It is recommended to charge Li-Ion batteries at a rate of 1C, where “C” is the capacity of the battery. As an example, it is recommended to charge a battery with a capacity of 800 mAh at 800 mA, or 1C. Charging at a higher rate may compromise the quality and lifetime of the battery.

Constant-Voltage (CV) Charging Mode

The battery voltage increases rapidly as a result of full-rate charging and once it reaches the programmable termination voltage of either 4.1V, 4.2V or 4.38V, the charger will move to constant-voltage charge mode. During this mode, the charge current gradually decreases while the battery remains at the termination voltage. The termination voltage can be selected to be either 4.1V, 4.2V or 4.38V by programming bits D6 and D7 in the Charger Control register to accommodate different battery chemistries. In CV charging mode, the Charge Control Status bits STAT2, STAT1 and STAT0 are respectively logic 0, logic 1 and logic 1.

TOP-OFF Charging Mode

When the charge current reduces to the EOC threshold (programmable to 5% or 10% of programmed full rate charge current), constant voltage charging will continue for an additional 21 minute TOP-OFF time period. In TOP-OFF charging mode, the Charge Control Status bits STAT2, STAT1 and STAT0 are respectively logic 1, logic 1 and logic 1. At the end of the TOP-OFF period, the charger transitions to Charge Cycle Complete.

Charge Cycle Complete

During Charge Cycle Complete, the charger is automatically disabled, regardless of the state of the Charge Enable Bit. In Charge Cycle Complete, the STAT2, STAT1 and STAT0 bits are respectively logic 1, logic 0 and logic 1. When the Battery Voltage drops below the VRESTART threshold, charging will resume in Full-Rate Charging Mode.

三、充电模式转换图

锂电池充电模式转换图如下,同样流程也可参考Max8671x 第29页插图。

镍镉(NiCd) 和镍氢 (NiMH)电池典型充电图如下,该摘自Fran Hoffart《快速、高效、獨立型 NiMH/NiCd 電池充電》一文P2:

 

 

参考资料地址:

http://www.ti.com/lit/ds/symlink/lp3910.pdf

http://datasheets.maximintegrated.com/en/ds/MAX8671X.pdf   

http://zh.wikipedia.org/wiki/镍氢电池

http://zh.wikipedia.org/wiki/锂离子电池

镍氢电池充电和放电曲线:

http://www.battery-china.com/html-new/xileng-b-cn.htm

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