The reason your playbook doesn't charge, is because the battery is required to operate the CPU so that the CPU can control the charger that charges the battery. If the battery voltage is below 3.53V (0%) then charging behaviour will depend on the software version your tablet is running. The charging code will limit the charging current to under 400 milliamps, during which time, it may take an hour to reach 3,53 Volts. Once the battery rises above this, the high-rate charging will begin.
The charger provided should be used to charge the device. The optional 12V rapid charger (purchased separately) may reduce charging times to approximately 3 to 4 hours. Standard Blackberry smart phone chargers, other AC adapter USB chargers, or computer USB ports are not recommended for the sole purpose of charging the Playbook as with these methods it may take more than 12 hours to charge your device.
If, after charging the tablet for 4 to 6 hours still does not result in LED activity, attempt to force power on the Blackberry Playbook using the Stack charging method. Here’s how:
1. Press and hold the power button for 30 seconds, then wait 15 seconds and press the power button for 3 seconds. This is similar to removing the battery for 60 seconds on the BlackBerry smartphone.
2. You can also charge the BlackBerry PlayBook for 12 hours, then try to power on by power and Vol + at the same time for about 15 seconds you should see the red LED. If it powers on connect it to the charger.
3. If the BlackBerry PlayBook does not power on at that time, then plug in the wall charger for 2 minutes, then unplug for 2 minutes. Repeat these steps 6 to 7 times. After plugging for the last 2 minutes, instead of unplugging the tablet press the power button. If at that time it powers on leave it charging for 6-10 hours. If the BlackBerry PlayBook still will not power on at that time you may need to reinstall the software.
You can find more help and support from the Blackberry PlayBook Support site.