Just catching up on this thread! Curious about one thing: are you filming long continuous takes or just short bursts? 4K on the ZV-1 makes it get super hot, which basically drains the juice way faster. I'm still kinda new to this but i'm realy cautious about generic brands cuz I've heard wierd stories about them swelling up in the heat... Since Wasabi was already mentioned, here is a quick look at two others: • SmallRig NP-BX1 Camera Battery and Charger Kit (2-Pack): These have better build quality than the super budget ones. They seem to handle the heat a bit better without feeling flimsy.
• Duracell NP-BX1 Replacement Battery: If you're paranoid like me, this is a solid middle ground. It's a reputable brand name with better safety circuits than no-name stuff. Definately watch those temps tho... it makes a huge difference. gl!

For your situation, i feel u... 4K is a battery killer. Basically: - Sony NP-BX1 Rechargeable Lithium-Ion Battery Pack ($45): Official tho pricey.
- Wasabi Power Battery (2-Pack) and Dual Charger for Sony NP-BX1 ($25): Great value, includes charger.
- BM Premium 2-Pack of NP-BX1 Batteries ($20): Super budget. I use the Wasabi kit and it works great. Honestly the best choice for all-day filming cuz i dont like overpaying. gl!

Lol I was literally about to post the same thing. Glad someone else brought it up.

TIL! Thanks for sharing