a few months ago I bought the MX Master mouse from Logitech and I really enjoy it, especially for the smart scroll wheel that can change from a ratcheting mode to a freewheeling mode. This is really handy for when you want to scroll through long documents quickly, but don't want to bother pressing buttons first to switch modes (even though that's also an option).
My biggest issue with the mouse, however, is the horrible battery life. Logitech advertises around 40 days of battery life with a daily use of around 6 hours. My results have been different though. I work with the mouse around 12 hours a day and it only last about 10 days (more or less).
After reading a few posts on broken scroll wheels I discovered that the internal battery is tiny compared to the size of the housing. In fact, it's just 500 mAh (3.7V) and its dimensions are 3.50 x 34.50 x 52.00 mm (thickness x width x length).
After some browsing through ebay, I found various batteries that have a similar size (just thicker) that offer double the capacity. From what I can see on the picture, it seems to me that there should be enough space vertically to fit a battery like that.
Now I am not sure what type of connector I need for the battery and I was hoping that someone from the forum might know how the original connector is called. If someone has some experience in hacking the MX Master I would love to hear about that too. ;-)
Also, if someone has some information about what I need to keep in mind when swapping batteries, I would be glad to know. :)