its round and flat
No, you can not charge a 3V battery with 12V charger.
2032 3V Lithium Battery
at the store
CR1616 - 3v battery
CR 2032, 3V lithium battery
3V 2 Triple AAA battery's
Cr2016 3v
3v battery is used direct current
The difference between the two is the 2032 3v battery is just one battery per package. The 2016 3v are sold in packages of two. Therefore, the 2016 would mean you would have 2 batteries to use. One to replace the battery that has died and one to save as a back up or to put in a second remote for your garage door opener.
V=IR R=V/I V=3V I=0.075A R=3/0.075 = 40 ohms
You can find out how to replace the battery on a rotary men's watch online through websites such as eHow, Rotary Watches, and Fixya. However generally it is just the replacing of the 3V batteries that look like coins available in the electronics section of most retail stores.
No set answer to that, it depends on the size/capacity of the battery and what it's powering.