JBL Charge 2+ speaker with no sound

Hi there, does anyone have any idea about what problem my JBL speaker might have? The speaker was fine at the beginning to play music. After two months it suddenly stopped producing sound when switched on. (the warranty for the product expired!). After that, it always gives low battery signal every time switched on; even tried with pressing call plus volume + combination buttons, pressing volume up button, checking the battery voltage of 3.8v between two red wires against the black wires. I guess the battery is not dead. Why the battery can't be charged to 4.2V, I have no idea. Bluetooth seems working when paired to iphone or android phone which provides the source of music.Even tried with audio in port with no success. After removed the battery pack with 5 wires (2 red, 2 black and 1 white in the middle), check the voltage from 5 male pins on the motherboard with original charger plugged in AC: 2.56V between 3rd pin (+) and one of other pins and 1.1mA current between 3rd pin (+) and any one of the other 4 pins.

My question is 1)that whether the battery pack should be charged to 4.0~4.2V in order to provides adequate power to the speaker or not; 2) how the 2P 3.7V 6000mah 22.2wh batter pack is wired up to have 5 wires (2 red, 2 black, 1 white); 3) how the battery is charged up with which wire through the motherboard via JBL original charger and at what voltage. Thanks in advance for your instructions, KM