I purchased the Greenworks 21 push mower a few months ago when grass just started growing. My wife continously was getting agitated about going through 2 AH batteries and not being completely finished with mowing and waiting another 30 mins for the used battery to charge to finish. After a month of listening to this I broke down and purchased a 4 AH battery and now she can finish the 1.5 hr cutting with 1 4 AH battery charge.
Mostly just a battery. I tried using the Bluetooth feature by downloading the appropriate app, however, it won't let me log in with my already established (and valid) credentials from the website. Anyway, I'm not really sure why I would need that feature, to begin with. As far as charge is concerned, it works pretty much just as well as the other 2Ah batteries I already own, I have not noticed any magical powers with it.
The battery provides enough power to let me complete bush trimming or chainsaw work without having to recharge. It is compatible with all my Greenworks tool. I only need one charger for my batteries.
I purchased this as well as a 2 pack of drill/drivers about a month ago. I need to replace the original battery that had come with my lawnmower. This holds a longer charge and is enough to cut my entire lawn. I absolutely love my Greenworks tools. I have a lawnmower, weed eater, pressure washer, and now 2 drill/drivers.