Yup. Those fast chargers are pretty sophisticated. I have been wearing out cordless tools for many years now, in the construction biz, and the recent improvements in the technology are impressive. Sure makes my work easier!
I learned several years ago that DeWalt chargers use what is known as "Delta V" charge sensing, which does not use any additional contacts. I found this out while researching bicycle headlights, and I have converted a charger for use on nicad packs for bike lights. You can use one to charge any battery pack made up of "sc" or the standard industrial nicad (ni-mh too) cells up to about 18 volts. One word of caution though! When you solder in some wires to carry the current to your battery pack, you have to be very careful not to touch either conductor, because there is 120vac on one conductor (to ground). I don't understand how that works, but apparently you can get a bad--even lethal--jolt from it. You can use an isolation transformer to make a safe system out of it. I bought a transformer a long time ago, but never got around to wiring it up. Anyway, the charger works great. You just use the positive and negative terminals in the charger, add wires and connectors, and hook up to the pack. The charger measures the pack's voltage every second as the pwm pulses go on and off, and when the voltage peaks and then drops slightly, it switches into slow trickle mode. Later model DeWalt chargers, like the one I converted, do have the third contact for the later battery packs, but the chargers are made to be backward compatible and will charge the old DeWalt two-contact batteries just fine. Or your RC car pack, or your 6 volt bike light pack, or other brand drill pack. Be very careful to get the polarity right, especially if you are going to charge low ah packs. The charger will beat the smaller packs to death if you get it wrong. Don't ask me how I know, just be careful. 
People who know a bit about the differences in nicad and ni-mh cells will note that delta v charge sensing is pretty tricky with ni-mh chemistry. I don't know of any DeWalt two-terminal battery packs that used ni-mh cells, probably for that reason. In the bike light realm, however, the chargers are still pretty dismal, even now, and in my experience, my hacked (and dangerous) charger works just fine with the ni-mh packs I have used it with. Many times more reliable and easier on the cells than the cheesy factory set ups.
