You have to trick the battery meter to show the correct reading in temperature protection mode according to this post on Vapor Shark's Facebook page.
Vapor Shark Hello Josh, The metering happens in real time only when the device is firing. If you are using a nickel coil and temperature control, you will notice that the meter will behave a bit erratically. Here is why, it is giving you a forecast of remaining battery life based on the last wattage level the device was outputting. Let's say you have a ni200 coil set to 420 degrees and 35 watts. At the beginning of the draw you will likely be close to 35 watts but as the coil comes to temperature the wattage level will be reduced to let's say 6 watts. When you let off the fire button the last wattage output was 6 watts and the battery meter is reflecting a remaining battery life forecast for 6 watts not the 35 watts. That is why, after 16 hours of use, you're still seeing a full battery. You can get an accurate reading if you just let the Wattage spike for the first second and then looking at the meter.