for filart -
There are a VERY few computers that use a rechargeable CMOS battery system and have a trickle charger circuit built in. The vast majority uses a non-rechargeable battery and as such do not incorporate a recharging circuit - no connection to a source voltage.
To recharge the battery there must be a connection to a source voltage. In the case where a NONRECHARGABE battery is used why would you go to the expense of adding a charging circuit - not cost effective. There is also the safety aspect as nonrechargable “Watch” batteries have a tendency to overheat and explode. You can recharge them with limited success – but it is just not worth it.
Requirement for attempting to recharge a nonrecharable battery.
Basically you would need a regulate source, voltage regulated to approx 10 to 20 percent greater than the battery no load voltage that decreases as the battery reaches no load voltage. The current must also be limited, normally 1/10th of stated amp hours (in this case milliamps. You could also apply a greater voltage, when it gets hot remove voltage be for it explodes - Just kidding.http://wiki.answers.com/Q/Is_a_cr2032_cmos_battery_charging_when_computer_turned_on
The CMOS battery is a non-rechargeable Lithium cell which powers the chipset when the machine is off. This prevents your mainboard's system time and BIOs settings from resetting each time the power is switched off. In other words, leaving the PC switched on will not charge the CMOS battery, neither will it damage the cell.
A 2nd sourcehttp://wiki.answers.com/Q/Is_a_cr2032_cmos_battery_charging_when_computer_turned_on
PS I've seen "how to recharge "watch" batteries - But as I said It's just not worth it.