I tried to replace old 500mAh NiMH batteries into my old siemens C35
by cutting off the 3 original batteries inside their plastic box
(there were 3 cells in series), and wiring in place 3 new AAA NiMH
batteries. I kept the small chip welded between the "-" contact
and the central contact, thus just replacing the cells.
Eventually a left the original battery pack in place, just removed
old cells and rewired the new AAA outside the cell to try if works.

But the phone does not work: it lights up for just seven seconds
the turns off, like with discarged batteries.
It however does charge the new AAA batteries such wired,
and i think it really recharges them fully at least (it needs 4 hours)

There is only one difference between new and old cells (alongside the
shape of course the new are 750mAh and not 500mAh.

What it's wrong?

bye!!!