Before I bought the GMC drill I phoned GMC and asked if the charger is automatic, ie: goes into trickle charge when fully charged and was told definitely YES, but I doubt that it was. One day if I think about it I may do some tests on the chargers, I still have both. These days, for my two B & D drill batteries I use a count-down timer to be on the safe side.
Using mains timer is a great idea for the health of Ni-CAD or NINH batteries.
My Ryobi chargers switches to trickle charge too but their circuit will overcharge and damage NiMH batteries because we cannot detect when NIMH batteries are already fully charged using rate of Voltage change alone.
Ozito charger and my Cabac drill charger just use a 500ma power pack + a simple transistor circuit to stop charging when battery pack reach a certain voltage. No reliable at all.
The circuit of the Metabo IC25 is quite complex. It does not just detect temperature changes - I tried to open up and understand but could not as I do not have the circuit or service manual.
"The gift of God is eternal life thru Jesus Christ our Lord"
Reuel - means "God's friend" (Heb)