Without an alternator, a fully charged race car battery starts at 12 volts and discharges down to about 10.5 volts before it is completely exhausted. The Total Discharge Controller (TDC) 50 will draw up to 50 amps from the battery, boost and regulate it to any desired voltage between 14 and 17 volts (in 1/2 volt increments).
It is perfect for short races (1 hour or less) where there is enough charge in the battery to meet the energy needs of the race car, but not necessarily at a high enough voltage for modern ECU's. Note that the TDC50-12 will provide fully regulated voltage to run more devices than the TDC30-12, but will exhaust the battery 40% quicker.
For more on how the TDC 30 can make a difference in your car, take a look at this blog post from our race at PRI in Seattle.