Originally posted by aslyfox having a common battery to use among your cameras may seem to be a small thing to think about
until you find yourself " in the field " with the wrong back up battery
Minor, yes, but I had three batteries for my K20 (= two backups) that all were useless when I bought a K5, for which I purchased two backup batteries, and those also serve the K3 and K1. If you get a camera that uses the same battery as one you have, you automatically get a backup. It's a small thing, but I was annoyed when the K2o batteries could not be used in a K5. I think in the current Pentax lineup, the K1, K1 II and K70 use the same battery, but the KP uses a different, smaller battery.