Overcharging Protection Chips Inside EVO’s Batteries.
Posted January 13, 2011 at 12:00 am by egzthunder1
Lately, there has been quite a bit of activity coming out of the EVO 4G fora. One of the biggest flaws of this device is the very poor battery performance, which unless a good kernel/rom combination is used, dies in less than a day, depending on the usage. Several members have been trying to get the batteries to reach their maximum capacity as there was supposed to be something in the kernels preventing it from fully charging. This fact could be easily noticed as the battery would drop anywhere between 4 to 8 percent right after being unplugged from the charger. As it turns out, and thanks to XDA member willy900wonka, the batteries are indeed equipped with over-current protection chips. The dev decided to take a battery apart and much to his surprise (or lack thereof), there was a small chip that has the following description from its manufacturer:
S-8205A/B Series Applications-Optimized-Battery-Protection Circuits.
All contained voltage detectors are of high precision between 15mV and 100mV depending on the function. Overcharge detection voltage is 3.55V..4.4V with 25mV accuracy. Overdischarge detection voltage is 2.0V..3.2V with 80mV accuracy. Discharge overcurrent detection voltage is 0.05V..0.3V with 15mV accuracy and charge overcurrent detection voltage is -0.05V..-0.3V with 30mV accuracy. The detection voltage in short circuit case is 0.5V..1.0V with 100mV accuracy.
So, to all of you who assumed that the SBC kernels could indeed override this, as there is a hardware protection in place, the device cannot be overcharged or rather charged past its safety limits.
You can find more information in the discussion thread.
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