Originally posted by DirkWitten Maybe there are some really good third party battery brands, i´ve tried Ansmann, Patona and VHBW (propably german brands too) and not one of this batteries are like the originals.
Like you, I've yet to find a third party battery with the same capacity as the OEM model. The OEMs are pricey, but worth it - although it's nice to have a few decent third party batteries for backup, which is how I tend to use them in any of my cameras.
I think the real answer to extended battery life with the KP is to use the grip. I don't own a KP, but I do have a Sony A7 MkII mirrorless which I suspect is even worse than the KP in terms of battery life (it certainly can't be much different), and I almost always have the battery grip fitted to it.