I recently upgraded from a pair of YS-27's to YS-D2's. I always used the 27's in manual mode (no TTL available). Now I can use both TTL & manual. With the 27's I knew about how many shots i could take on a set of batteries. Now I'm having trouble trying to figure out the number of shots that I should be able to get in TTL mode. I'm using PowerEx 2700's. Since TTL is new to me I'm using it most of the time. I never know when the strobes will fire their last shot. For a given exposure, will battery consumption be different with TTL vs manual? Any recommedations or suggestions greatly appreciated.