I satisfied despite mounting problems

The mechanical opening of the e-toothbrush no problem. However, I had while desoldering the old batteries major problems:
The heat generation of the soldering iron (free addition) was not enough for desoldering.
I then cut by side cutter the contact lugs of the old batteries, installed the new battery and thereby shortened the new flags, slid under the remains of the old flags and fixed.
To my great delight it worked after several charges, so
UNFORTUNATELY: Now, after about nine months, the battery will discharge totally at each use. I'll have to dispose of the part.
Have disposed of and me a "Braun Oral-B Vitality Precision Clean Electric Toothbrush (with timer)" bought for 17.95 and am now satisfied. sa my local review