LG -V521 User Manual page 14

WARNING
Use only LG-approved chargers, batteries and cables. If you use unapproved
chargers, batteries or cables, it may cause a battery charging delay or display
a pop-up message regarding slow charging. This can also cause the battery
to explode or damage the device, which is not covered by the warranty.
NOTE:
Your device has an internal rechargeable battery. For your safety, do not remove
the embedded battery.
The battery must be fully charged initially to improve battery lifetime.
2. Connecting a USB device to your tablet
Getting to know your device