Sennheiser XSW-D - Replacing the battery

The Sennheiser XSW-D wireless transmitter unit (part of their XSW-D pedalboard set offering), has excellent range and clarity paired with the small form factor and has been my choice for years. I've used it for my guitar on rehersals and gigs since the base unit sits on the pedalboard and contains a D.I. out and tuner function (most likely a buffer too). A very sturdy solution!
https://www.sennheiser.com/en-us/cata...
However, the battery has been draining faster and faster so I need to replace it with a new battery. It used to be easy 5-6 hours of usage, but it's nowadays down to 2h tops.

Watch this video to learn how that can be done.

00:00 introduction and background
02:41 starting to pry on the chassie.
08:00 opening the unit.
10:20 removing the old battery.
11:03 comparing the old battery with the new.
12:00 difference between the old and new. more hacking needed.
13:46 removing the old safety circuit from the old battery.
16:16 remove casing of the new battery to fit the old safety circuit and connection wires.
21:07 checking out the circuit in detail.
22:04 removing the circuit on the new battery, making way for the "transplant".
24:59 start soldering the old circuit to the new battery.
28:40 wrap electrical tape to fixate and protect the battery and the connections.
31:08 reassembling the unit.