load without causing damage.
The C12 monitors the electrical power to the motor to ensure that the motor operates within safe parameters. However, make no mistake; the C12 was designed properly in the first place, so it won't overheat under normal use. The drills mentioned above were
Power Control
Virtually all drills on the market (including AC and DC motors) use a similar design for controlling the power to the motor. The trigger switch contains all of the electronic controls.
A small electronic circuit creates a pulsating signal for controlling the speed of the motor, and a mechanical switch controls the motor's direction (refer to How Variable Speed Controllers Work on page 5). All of the power to the motor passes through this small circuit, and what's more, passes through the mechanical contacts of the forward/reverse switch.
The C12 uses six high power amplifiers to control the power to the three phases of the motor. These are located on the main control board where there is ample room for a heatsink. The only control circuit inside the power trigger is a small, solidstate resistor that is part of the frequency generator circuit.
Even the forward/reverse control of the C12 is solidstate. There are no moving parts or contacts
1This is not a new concept. U.S. tool manufacturers frequently overstate their claims for marketing purposes. Festool does not play these marketing games.
to fail. It is a sensor that detects the position of a rare earth magnet located on the push button. More importantly, the electrical power of the motor is not flowing through a set of switch contacts like it does with other drills.
Battery Sizes
Whether you're an occasional picture hanger, or a professional contractor, the C12 is flexible enough
to meet everyone's needs. The C12 is available with three sizes of batteries to choose from: 1.3 Ah NiCd, 2.4 Ah NiCd,
and 3.0 Ah NiMH.
The higher the
Battery Protection
There are two common ways that battery life gets shortened;
battery charger to prevent over charging. The microprocessor controlled charger rapidly charges the battery, and when full
charge is detected, the charger switches over to
maintenance mode.2
A common misconception with tool batteries is that they should be fully discharged before recharging. While there is some truth to this, fully draining a battery to the point of stalling the motor can actually cause permanent damage to the battery. The cells inside the battery pack can actually change polarity, called cell reversal, under deep cycling. The C12 monitors the battery to determine if it is capable of providing the power required. If the battery cannot supply the power
2With daily use, the batteries can be left in the charger until needed. However, the charger should not be used for long- term storage of infrequently used batteries.
2
