when Sony updated the firmware for the A6700 last year, apart from fixing some bugs, they 'discouraged' the user from making use of 3rd party batteries, with the rather alarming message above. (I gather the same message appeared in other recent Sony cameras after updates) with this message appearing with batteries that were behaving normally prior to the update. They can still be used, but with the battery life percentage display removed, and the message recurring each time the camera was switched on.

Although K & F Concept have not listed the A6700 as compatible, it certainly is, and it is "goodbye!" to the 'error' message above.

An immediate advantage over the OEM battery is the inclusion of a USB C port for charging (possibly to update the battery firmware in the future if needed?) and a cover plate to protect the battery contacts and USB socket when not in use.

In my own test, the battery life of the K & F Concept battery at least matched the original - I cannot comment on the longevity of the battery (it is new) but, having several other products from K & F Concept, suspect that the quality of their battery is going to be very similar to Sony's.

If the battery fails in what I consider to be 'early', I'll come back to the review and correct my opinions.

This K&F Concept battery has the same specs as the original: 7.2V, 2280 mAh, 16.4 Wh.
It can be charged on my Sony charger; I like the fact it can also be charged by just plugging in a USB-C cable and the mini-LED light signals the charge state with either green or red -- I don't get the exact level from that mini-LED though. When I connected the battery to my power bank it has drawn 10W power.
It performs subjectively very well, and I like the color feature of the battery also very much. I take several batteries with me on a shoot and being able to identify them by color helps me picking the empty or full ones easier. The cover protects the contacts and the USB-C port from dust and crumbs.

I love the new USB-C port that companies are putting on NP-FZ100 batteries. It makes it so much easier to charge up in the field with a larger battery pack, so I can alternate between two NP-FZ100s with a battery pack and be ready to go all day, rather than having pockets for charged and then discharged batteries.

Plus, I can forgo a specialized charger if I'm on a trip and want to just bring one big USB charger for all my electronics.

I just reviewed a non-name-brand 2-pack of these batteries, and they were too big for the camera's battery slot (even before any chance to heat up from use). That's scary, since it could ruin the camera trying to pry one of them out.

I didn't have that problem with this one, or with another popular trusted brand's version. They've worked fine in the field. I've been happy with products from K&F Concept, so I'm fairly confident recommending this one.

These are a decent bunch of batteries from K&F Concept. The USB Type C charging port is a feature I welcome very much.

It has similar battery life to the OEM Sony NP-FZ100 batteries. I definitely think this is a great hit for anyone that's looking for batteries on a budget but still wants to power up their camera with confidence. I'll be using this for work, and I think it's still a great option for that.

Game-changer for my Sony camera! This NP-FZ100 battery charges in a flash with the Type C port.

I’ve been using this battery for about two weeks in a Sony A6600. The original battery, NP-FZ100, is long lasting. I shot 50 photos with this battery at full charge with minimal discharge of less than 99%, which is normal with the original battery. After a week of non-use the K & F Concept battery was still at 99%, which is very good. Both batteries have the same 2,280 mAh. I’m giving 5 stars as the battery performs. The only advantage I see is the battery can charge without a charger outside of the camera. As it’s possible to charge any NP-FZ100 battery in camera. If you do need to change this battery on the go you only need a USB-C cable and a charger or car adapter to charge this battery. One less item to pack in the bag!

I tend to keep a lot of extra NP-FZ100 batteries on hand for long back-to-back shoots and this is a great replacement battery/battery to add to your collection. Functions as well as an OEM Sony battery with the benefit of being able to charge them while you're on the go without needing to bring a specific NP-FZ100 battery charger (e.g., via USB-C in the car, at your hotel, etc.). Currently use this as my primary battery/always leave it in my backpack in case my batteries die on me so I can at least charge up one battery while I'm away from my charging station in my office.

Excellent value for money and long-lasting charging, which also supports the original charger.

Used for a sony 7c works well. Equipped with a charging port, it is much more convenient to charge than the original.

Used with A1, no warning from the mirrorless of non-original battery... Practical is the possibility of charging it via the camera, with the Sony charger or with a USB C cable. As for duration I would say it is similar to the original...