Actually, a good replacement for the stock battery. Maybe more. For G7, GH2 &c. possibly the new G85

I use a lot of the BLC12 Batteries. I buy the Panasonic ones; they aren't cheap but they last the longest and don't turn the camera off with no warning.
However, I do buy aftermarket batteries for testing from time to time. They often have very high ratings, and they never work very well.
A few years ago, I bought the DSTE "1600mah" battery. It had about 70 percent of the stock battery's power, and the stock battery is 1200 mah. So that's 840mah, or about half the advertised capacity.
A few weeks ago, I purchased the 1700 mah version at this link:
https://www.amazon.com/dp/B00MEAMBQU
It weighs 55 gm as opposed to the stock 50gm. Previous clones weighed 46 and 48 gm.
Now before you get excited, the extra weight is probably ballast, since you can't squeeze more cells into a battery, as a general rule.
However, after extensive testing, this battery is equal to--not better--but equal to stock. The only difference is that the shutdown curve is a bit steeper.
So it isn't "1700" mah, but it is basically a stock battery.
This was quite a shock, but I repeated the tests several times. In one test, I simply turn on the camera and record video until the battery croaks, and measure the time. Both the stock battery and the DSTE run the G7 for two hours of video, sometimes a few minutes more, sometimes a few minutes less. So, finally, an inexpensive option. At least for this batch. Also, see my post on the cheap external battery that will run your camera all day.