Any one able to use 3rd party batteries? If so, which brand?
I use the
Patona Platinum for EN-EL15c in my Z8 and I am happy with them. According to the spec and label they have a slighlty different chracteristics:
EN-EL15C: 7,0 V, 2280 mAh, 16 Wh
Patona: 7,2 V, 2400 mAh, 17,3 Wh
I dont't have them long enough to be able to make a statement regarding durability for this particular model, but so far I've had no problems with them what so ever.
I use Patona batteries already quite for quite a while already since DSLR times (can't recall exactly, but it must be almost 10 years) and never had problems with them, neither with EN-EL15 replacements nor with EN-EL18 replacements. The latter I used quite a lot with my D4s and my gripped D850, before i switched to mirrorless and for the Z8 had to go back to EN-EL15.
The only "problems" I can recall were incompatibilities of older models with newer comera generations, but this is more due to the fact that Nikon changes their chip coding for the batteries with new camera models being introduced than a consequence of something being wroing with the "analogue" part of the battery. But this is something that can happen even with Nikon batteries. I don't have a Z9 and thus don't use EN-EL18 anymore, but my friend told ma about incompatibility issues with older types of original Nikon EN-EL18 batteries. He simply couldn't charge the older EN-EL18 batteries with the latest MH-26 supplied with the Z9.
Using the Patona EN-EL15 for shooting, I can't see any difference in behaviour, everythings works fine. Neither early discharge, nor functional errors or error messages from the camera. The capacity difference IMHO lies within the tolerance in power consumption caused by different shooting behaviour (more or less display, switching camera off versus standby,...)
Charging is the same, no matter whether I use the Nikon charger, a USB travel charger or charge them in the camera via USB. They simply behave like a normal EN-EL15.