A battery charger is almost a must-have in my opinion if you own a GoPro. If you don't have a separate battery charger, your GoPro is stuck connected to a plug and you may be missing out on some special footage you could've otherwise captured. Having said that, the obvious precondition to owning a battery charger would be an extra battery.
Personally, I love capturing videos of my pup, Coco. Owning a battery charger made a world of difference in terms of how readily I can take videos. My GoPro is always ready to go and I almost certainly have at least one battery charged and ready to quick action.
There are quite a few different options for battery chargers, but personally I ended up getting the TELESIN Allin Box Battery Charger. I landed on this one because I like to explore a lot with my pup. I use the battery charger as a casing as well when I'm out exploring and the fact that it's waterproof won a lot of points for me.
Also I'm not exactly sure what material that used it, but the outer material feels like rubber and it has a bit of cushion to it. So I feel safer knowing that it can absorb a bit of shock. I haven't tested it on a hot sunny day so I'm not sure how the material will hold up then, but I most likely will just keep it hidden from direct sun by putting inside the bag so it might not be such a big deal.
TELESIN Allin Box Battery Charger is also very versatile. It can charge up to 3 GoPro batteries at the same time. And it can also hold 3 MicroSD cards which is perfect for carrying extra batteries and SD cards if you are going for a long shooting day.
When you are charging your batteries, there's an indicator light for each battery so you know the charge status for each. Also one the MicroSD card slots can actually be used as a flash drive if you connect the battery charger to your computer via a USB C cable.
Only complaint I have with the product is that the plug cover for the USB C plug is a bit loose, and comes off easily. So even though it's waterproof I plan to still take of it rainy conditions and ensure that plug area doesn't get submerged into water.