Neuxs 6P的意外掉电故障

去年12月起,大量Nexus6P用户遇到了在电池仍有足够电量(60%-15%)时掉电并关机的情况。从上周开始,我的手机也毫无预兆地出现了同样的问题,而且比网上大多遇到同样问题的用户更严重,意外掉电发生时的电量为50%-80%不等。

原因

在问题最初爆发时,在Reddit上就有大量用户在讨论,分析如下:

Reading through the battery issue threads, I’ve seen a few arguments about whether the early shutdown problem is due to a hardware or a software problem, so I figured it might be useful to add a bit of information about how the battery system works.
In short, the phones are probably shutting down early because the performance of the battery doesn’t match the calibration of the fuel gauge software.
The idle (no-load) voltage of a li-ion cell ranges between about 4.2V when fully charged and about 3.3V when discharged. These values vary a bit from one phone model to another, but not by much. If that was all there is to it, it would be very easy to have a reliable battery gauge, but there’s another factor:
All batteries have a certain internal resistance, and the internal resistance dictates how the battery responds when you draw power from it. When you draw current from a battery, the output voltage will sag, and it’ll recover when you stop drawing current. So the phone may show a 75% charge level and the battery may be sitting at 4.0V. You start the camera app and because the camera is relatively power-hungry, the voltage drops to 3.8V. You close the camera app and the voltage recovers to 4.0V. The higher the internal resistance, the larger the voltage drop.
The internal resistance and the resulting voltage drop is a potential problem because these phones need a certain minimum voltage to function. Even if there’s still plenty of juice inside the battery, if the momentary voltage drop is too severe, the voltage will drop below the minimum threshold and the phone will shut off.
There are several factors that have an influence on the internal resistance:
State of charge. The internal resistance goes up when the cell is discharged.
Health of the battery. Old cells have a higher internal resistance than new ones.
Temperature. The colder it is, the higher the internal resistance.
This is also why some Samsung phones won’t let you use the camera when the battery is at 5% or lower. There’s still juice in the battery, but power-hungry loads like the camera would cause an excessive voltage drop at this state of charge, and the phone would shut off prematurely.
When calculating the percentage, the fuel gauge system makes certain assumptions about the internal resistance and how the battery will perform under load, and if the predictions don’t match the reality, the phone will shut down even though the fuel gauge may still be showing 25%. It expects a small voltage drop, but the battery can’t cope with the current draw, the output voltage dips below the minimum operating voltage of the device and it shuts off.
If you’re out of warranty, a new battery would probably cure the problem since it’s going to have a lower resistance. If you want to mitigate the problem a bit, keep the phone warm and turn down the brightness of the screen.

读过关于电池问题的讨论后,我发现了一些关于意外掉电问题是由软件还是硬件问题引起的的争论,所以我想讲一下关于电池系统是如何运作的。
简而言之,手机提前关机是由于电池的性能和电量统计软件的校准不符。
锂离子电池的空载电压大约介于4.2V(满电)和3.3V(没电)之间,这个数据在不同的设备上有所不同,但不会差距太大。如果仅仅是这样,那么可靠地测量电池电量是很容易的,但是我们需要考虑另一个因素:
所有的电池都有一个特定的内阻,内阻会影响电池的放电性能。当电池放出电流时,输出电压将会下降,当停止放电后电压会恢复。所以,当电池放电电压为4.0V时,手机可能会显示75%的电量。当你这时打开相机App,由于相机是耗电大户,电压可能下降到3.8V,当你关掉相机,电压会恢复到4.0V。内阻越大,电压下降越多。
由于手机需要一定的最低电压才能正常工作,内阻和内阻导致的放电电压下降会使即使电池内还有足够的电量时,手机也会由于电池电压低于所能支持其工作的最低电压而关机。
影响电池内阻的有下面几个因素:
1. 充电状态:电池放电时内阻升高。
2. 电池健康程度:旧电池有比新电池更高的内阻。
3. 温度:温度越低,内阻越高。
这就是为什么一些三星手机会在电量低于5%时禁止使用相机。因为即使电池内仍有电,但是相机带来的较大负载会导致较大幅度的电压下降,手机就会关机。
当计算电池的电量百分比时,电量计算系统已经为内阻和电池在较大负载下的性能做了相应的预设。如果预设不符合实际,则手机会在可能显示剩余25%电量时关机。因为预计的电压下降较小,而电池无法承受当前的放电电流,电压下降到设备的最低工作电压之下,因此手机就关机了。
如果你已经过保,一块新电池可以解决这个问题,因为新电池的内阻较低。如果你想要减轻问题,保持设备温暖并调低屏幕亮度。

解决方案

如上文所述,更换电池是最简单粗暴也最有效的方式。直接淘宝一块电池回来换上,就可以满血复活了。电池花费大约60软妹币。
iFixit给Nexus6P的评分是2分,分数越低越难拆解。动手之前可以先看一下iFixit的拆解过程,对什么位置有什么部件心里有数。
首先移除背面的玻璃和塑料片,这两块都是用胶粘在后盖上的,并且和周围紧紧贴合,如果强拆的话很容易弄坏玻璃片。我的建议是先用电吹风加热,然后用美工刀撬开一个角之后把撬片伸进去把胶划开。
移除玻璃和塑料片之后,一共有6颗螺丝,其中有两个是被白色胶纸盖住的,不要忘记。

在拆卸后盖时,iFixit上是这么拆的,不过不要相信这种方法。因为后盖的周围有一圈暗扣,强行拆是肯定拆不开的。建议用锐器从USB口附近插入,然后把机身从后盖里面撬出来一部分,然后用翘片把侧面的暗扣划开。

打开机身之后就可以开始拆电池了。这个电池的安装方式很反人类,是被红框位置的两片强力胶粘在后面的屏幕总成上的。同时,电池下方有屏幕排线,因此不要试图加热或使用任何锐器。建议用翘片从蓝色框位置的豁口插到电池下面将电池翘起一点,同时用卡片一类的东西把电池下面的胶划开。电池拆下来的时候已经有一些变形了,我都有些担心它会不会boom。

拆下电池之后就好办了,把新电池装上之后,把所有部件依次装回去即可。不过我的新电池和旧电池的尺寸有一些微小的差别,导致电池排线不能完全伸展开,不过应该不影响正常使用。

新旧电池对比:

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