Lithium ion cell voltage not going up after 3.8V

[tmho]

I got a chromebook with battery problem. It was charging when plugged in. But the indicator just showed that the battery was below 10% no matter how long it was plugged in. I took the battery pack out. There are two cells in series. Each cell had a voltage of about 3.7V. I charged one of them with a lithium cell charger. I can see current going into the cell at about 500mA. After several hours, the voltage was just about 3.8V. I charged it again manually by connecting 4.2V to it from a power supply and set the maximum current to 500mA. I can see about 100mA going into the cell. But the voltage was still 3.8V after several hours. I have never come across such situation. Can somebody tell me what is wrong with the cells?

Some more information. I do not have the original power adaptor or charger. The markings on the chromebook show that it needs input of 19.5V. The markings on the battery pack show that it is 7.7V which I think is the nominal voltage. Therefore, I think the maximum voltage of each cell should be 4.2V.

 

[harrisonpatm]

This is what old cells do. They're self-discharging; you're giving it 100ma, and it's bleeding out 100ma as you're doing it. It's a dead cell, recycle it.