My lume pad 2 Charge too slow, how I fix?

Hello everyone, So I buy LumePAD 2 & receive it yesterday. I noticed when docked, it charge but battery level rise only when I not touch it & when screen off. If I use it or any app while it on dock, then it show bolt, but charge not go up. If I use 3d mode look at photo, in 15 minute it go 100% to 85%, if I look at video in 3D, it go 100% to 70% in 15 minute. Why 3d drain battery way it do & is there way so I able use it while it charge and it stay 100% as long I keep plug in?

I use charger come in box only, no other charger.

It doesn’t come with a charger in the box.

You need to use a charger that does at least 33W+ to charge faster than the battery drains, and you can use chargers that are 60W+ for supercharging.