Note 3 was one of the best Smartphone, However, it was from software side where several users complained to have issues including lag and battery drain.
Smartphones are very power hunger. Stock battery will last at most one day or less under normal usage. But this Note 3 user came up with an insane idea and modified his Smartphone's battery.
He used 3 3500mAh 18650 Rechargeable Lithium Li-on Batteries and modified the device's internal to enable external power supply. He also used a Lace-up Case to cover the hideous back. The Modder claims that the Mod can be removed easily and is 100% reversible.
Note that this Mod is not 100% safe and your battery may catch fire, melt or possibly explode.