When I charge new device with old charger, device is not charged properly.

First of all, if you hope to charge the new device, we recommend to use the main Samsung–approved charger
supplied with your new device package.
If you use the existing old charger according to situations, it may happen that the charger
may not provide enough power for your device to charge. So, your device may not charge
or take longer to fully charge the battery than usual.
( *Reference : The charger that has the same output current value with current value which
your device need is the best available.
ex: Galaxy S2 : 0.7A, Galaxy S3 : 1A, Galaxy S4 : 2A, Note 2 : 2A, Tab2 10.1 : 2.5A)

At that time(If the device is not charging properly), please take the device and the charger
to an authorized Samsung Service Center in the near area.
Besides, use only Samsung-approved charger. Unapproved chargers or
cables can cause the battery to explode or damage the device.
Any damage caused by misuse is not covered by the warranty.