I've gone through a bunch of these over the years and found these two reliable:

• Patona Protect DMW-BLK22 2250mAh
• Has heat sensors and fire-resistant casing. These are great if youre shooting long clips and worry about temps.
• Powerextra DMW-BLK22 2250mAh 2-Pack
• Dirt cheap and reliable enough for secondary use. They usually work fine, but some older batches dont always report the battery life percentage perfectly on the S5II.

Regarding what #1 said, im actually super satisfied with Neewer DMW-BLK22 Replacement Battery 2250mAh over SmallRigs. They outlast my Watson DMW-BLK22 Li-Ion Battery and havent glitched once tho, totally recommend them.

To add to the point above: I have been really satisfied with the performance of the Hahnel Extreme HLX-B22 Li-Ion Battery 2200mAh. If you are worried about reliability during a wedding, these things are legit. They use high-capacity cells that dont sag as much as the generic ones when youre pulling a lot of current for high-res video. Heres why they work well for my workflow:

• Silicone injected casing makes them super shock resistant and durable
• Zero communication errors or lockups even during 4:2:2 10-bit recording sessions
• The voltage stays very stable throughout the entire discharge curve I also have no complaints about the K&F Concept DMW-BLK22 2250mAh Battery. The USB-C port is handy for charging in the car between locations, but the Hahnel is definitely the one i trust when the pressure is on. Its a bit more expensive than the bargain bin stuff but still saves you a ton compared to OEM.

Oh man, congrats on the Seattle gig! That city is gorgeous for photos. I totally feel you on the battery drain though, the S5II is a total beast but it's thirsty as heck. Forget those 80 bucks official ones, they're highway robbery lol. Testing out the SmallRig DMW-BLK22 USB-C Rechargeable Camera Battery 2250mAh was a game changer for me and they are freaking life savers. The best part is the USB-C port right on the battery itself. You can literally charge them in your gear bag with a power bank while you're shooting! Haven't had a single error message on my S5II or my old S5 yet. If you want something even cheaper that still rocks, the Wasabi Power DMW-BLK22 Replacement Battery 2250mAh 2-pack is usually super reliable, but seriously, get the SmallRig ones for the USB charging. It makes wedding days way less stressful when you aren't hunting for a wall outlet!