JJ you need to clean your PM box! Ambient temp will affect your battery life. Last night it was under ten degrees and I ran a battery down fast shooting the eclipse. The 100-400 isn't the best low light lens so extra AF hunting added to the consumption. Two batteries are a must. I've learned to keep one charger at home and one in my bag. Good choice on the TC. It's a quality piece of gear. If you need more batteries I highly suggest you google Sterlingtek. They are a fraction of the price and last even longer.
