As an engineer I pulled some info from the datasheet for the chip the nook uses, it may help better understand charging issues.
full datasheet is on the TI site at:http://www.ti.com/lit/ds/symlink/bq24196.pdf
If you connect the nook to a low power pc port you will only be able to run the charging for 45 minutes before the charger IC stops. To start it again you have to unplug and re-plug the USB cable. The charge current for a 500ma usb port is about 440ma.
The device fast charges at 1.5A using the charger and charges at 4.208V to the battery. The bad battery setting is for 1.8V, so if your device battery falls to that level it will not charge because the chip assumes a failed battery. I see this a lot in tablets. Someone stops using the tablet when the charge is 10% or less and then 2 weeks later picks up the tablet and it appears dead. The battery cells have discharged below the limit and now will not charge. The device will consume power even if you power off the device because the charging controller is on 24/7 regardless of any mode except shipping mode which we do not have access to . Fix for dead battery is remove the battery from the tablet, charge on external charger , replace.
if you want the info on your own charge stats just type dmesg in a shell prompt.
data to look for is like this:
full datasheet is on the TI site at:http://www.ti.com/lit/ds/symlink/bq24196.pdf
USB Timer when Charging from USB100mA Source
The total charging time in default mode from USB100mA source is limited by a 45-min max timer.
If you connect the nook to a low power pc port you will only be able to run the charging for 45 minutes before the charger IC stops. To start it again you have to unplug and re-plug the USB cable. The charge current for a 500ma usb port is about 440ma.
The device initiates and completes a charging cycle without software control. It automatically detects the battery
voltage and charges the battery in three phases: pre-conditioning, constant current and constant voltage. At the
end of the charging cycle, the charger automatically terminates when the charge current is below a preset limit in
the constant voltage phase. When the full battery falls below the recharge threshold, the charger will
automatically start another charging cycle.
The device fast charges at 1.5A using the charger and charges at 4.208V to the battery. The bad battery setting is for 1.8V, so if your device battery falls to that level it will not charge because the chip assumes a failed battery. I see this a lot in tablets. Someone stops using the tablet when the charge is 10% or less and then 2 weeks later picks up the tablet and it appears dead. The battery cells have discharged below the limit and now will not charge. The device will consume power even if you power off the device because the charging controller is on 24/7 regardless of any mode except shipping mode which we do not have access to . Fix for dead battery is remove the battery from the tablet, charge on external charger , replace.
The USB ports on personal computers are convenient charging source for portable devices (PDs). If the portable
device is attached to a USB host, the USB specification requires the portable device to draw limited current
(100mA/500mA in USB 2.0, and 150mA/900mA in USB 3.0). If the portable device is attached to a charging port,
it is allowed to draw up to 1.5A
if you want the info on your own charge stats just type dmesg in a shell prompt.
data to look for is like this:
Code:
<7>[224884.880706] bq2419x_is_vbat_in_range: vbat = 4135000
<7>[224884.881378] bq24196 1-006b: bqSetSYSMIN: 3200
<7>[224884.882019] bq24196 1-006b: adj_fast_ichg_lim: 2036, 240, 2036
<6>[224904.594329] android_usb gadget: high speed config #1: android
<7>[224904.594818] bq24196 1-006b: USB_EVENT_ENUMERATED
<6>[224904.595306] android_work: sent uevent USB_STATE=CONFIGURED
<7>[224904.600708] bq24196 1-006b: INTERRUPT 08=6c, 09=0
<7>[224904.600952] bq24196 1-006b: S: Power Good
<7>[224904.601165] bq24196 1-006b: S: CHARGE STATE = 2 (FAST CHARGING)
<7>[224904.601531] bq24196 1-006b: S: VBUS STATE = 1 (USB host)
<7>[224904.601745] bq24196 1-006b: S: Dynamic Power Management enabled