to determine the amperage draw run the 12 volts in series thru an
ammeter while you drill a 3/8" hole in a 2"x4" piece of wood to load
its motor. size the fuse accordingly to be in series with the cigar
lighter male plug which is already protected to 10 to 30 amps by your
vehicle. there is probably a cigar male plug with fuse at radio shack
or pep boys. or read the technical information on the label. or simply
shop for less expensive replacement batteries but do the homework on
the battery type to match the charger type. we prefer the 12 volt
makita cordless drills and found a replacement battery with a built-in
led light on it that illuminates the drilling area. watch the weights
as the drill voltages go up you may find some 18 volt construction duty
cordless drills are excessive weight for minor occasional household
uses or at the top of an extension ladder playing with the gutters. use
a regular 110 v drill for major wood drilling jobs reduces wear and
tear on your battery drills.