This must have been discussed in the past, but it is so general and there are always new members so it is worth raising. I gather from the internet that Li ion batteries are best stored at about 40% charge, where they degrade about 3x more slowly than fully charged, and should not be allowed to drain. It's not very convenient to have half-charged batteries when you have to grab extra ones for a shoot. So do people actually store them half-charged?

What prompted this is that I just checked the LP-E6 left half charged and very rarely used in my 7D. It read in the menu 46% charged but the previous two green bars for Recharge Performance had dropped to a single red.

So, is it bad practice to leave the battery in a camera for long periods unused? Does the red bar mean that it is now shot (I'll find out later myself this weekend)?