Reply To: How I extended the battery life of the Cube i7 Book and Fixed Palm Rejection

[Ben]

maus wrote:

The bad news: I noticed that the battery discarging rate that the tablet provides is not accurate at all, it seems to be only about 82% of the real discharging rate! For example, during the video test with brightness set at 25%, BatteryBar told that the battery was discharging at about -4.600 mW, but the real discharging rate was -5.600 mW. In fact, if you divide the battery capacity (about 41 Wh) for 5.600, you get about 7, that is the number of hours you can squeeze from the battery in that scenario. And it also seems that Windows 10 calculates its estimation of the battery runtime by using the average discharging rate, so if your battery is going to last 7 hours, it will tell you that you have about 10 hours left! That’s pretty annoying, I don’t know if it can be fixed by software (maybe with a BIOS update) or if it is an hardware issue.

 

Good observation but wrong conclusion.  Actually the capacity of the battery is nowhere near 41 Wh (reality: 4200 mAh * 7.6V = 32 Wh).  Use the correct capacity in the equation, and now you see that the discharge rate of 4600 mW matches closely with your observed runtime of about 7 hours.

It would be very surprising if the discharge rate were incorrect, since that is actually *measured*.  BatteryBar should eventually recalibrate the capacity based on actual power released and replace that ridiculous 41 Wh estimate by the real value.

(For those who care — a Li-ion cell ranges from about 4.3V at full charge to 3.6V at about 2% charge remaining, with two batteries in series the voltage is twice that.  The voltage also doesn’t decrease linearly with energy remaining, which results in the “average” voltage being a somewhat below the midpoint between 3.6 and 4.3V.)