Gigaset batteries charging problem

[Giga_set]

I have a GIGASET 3000 Comfort handset connected to a GIGASET 2011 base
station. My handset behaves in a strange way regarding rechargeable
batteries. A couple of weeks ago the charging status indicator on the
handset's display modified from batteries full -> batteries 2/3
charged -> batteries 1/3 charged -> =
batteries flat regardless of the fact that the handset was in the
GIGASET 3000 charging unit and the charging indicator flashed
suggesting that the batteries were in the charging status. The problem
is that the batteries never charged but one morning I found the
handset off although it was placed in the charging unit!
I replaced the batteries with a couple of brand new ones, placed the
handset in the charging unit an prepared myself to patiently wait for
the 16 hours first charge. The batteries 1/3 charged indicator began
to flash signaling the charging process but after a few hours I found
again the handset off in the charging unit! Each time I tried to
charge the new batteries happened like this.
I took the batteries and charged them in the base station for 16
hours, placed them in the handset, the charging status indicator
displayed batteries full and used the handset without recharging a few
days until the batteries were flat again and the handset went off. I
placed the handset again in the charging unit but again after a few
hours I found the handset off!
If I use the base station to charge the batteries, insert them in the
handset and place the handset in the charging unit the charging status
display that indicate batteries full will begin to flash signaling
charging in progress. But instead of charging the batteries the
process is weird, after a few hours the batteries 2/3 charged will
flash, and after another 5-6 hours the batteries 1/3 charged will
flash and tomorrow morning I will find the handset off in the charging
unit.
I look forward to hearing from you,

John