It could also be that you're not used to the dual coil. The bf has one of those and when we switched him from BDC to BVC, he had a hard time adjusting to the fact it empties juice a lot faster.
Also, from our experience, the BVC coils are kinda hit or miss. We've had two bad ones from the current box of five, and we're only on number three. Don't know why, but they were just flooding juice out the 510, which is really bad on a LVT. (It's not a sealed 510 connection, dumps right into the case.) If he left it in his backpack during the work day, it would empty 90% if a tank worth.