I too have this battery drain issue on my SPro 3. Nevertheless, this is the perfect tablet/laptop I've ever had!
How they expect someone buy their products with all these problems with surface line of devices. I want to buy surface book but I have no confidence in using their products seamlessly.
In other words, the life of your battery is in the hands of money making minds.
How can a hardware problem be addressed by software, maybe it will show remaining battery in slow mode, ONE full charge, per one session of 3 hrs max