I just hope this does not cause a shortage of batteries and accessories for the 18V line. The main reason for DeWalt to release the "20V Max" series is to fully integrate the LiIon technology into the tools themselves. The 18V LiIon line was thankfully made backwards compatible, but that left the entire line as a bit of a kludge. Since the NiCd days, the tools themselves are rather "dumb" in that there was no overload protection, cell protection or any sort of battery management built into the tools in the beginning. To retrofit LiIon technology into the old tools, the battery management and protection circuitry had to be built into the battery packs themselves. If you compare the NiCD and LiIon packs, the "stem" of the NiCd contains one of the cells that make up the pack, where the LiIon packs housed a complicated battery management module in the little space. There is no communication between the tool and the pack like there is in fully integrated LiIon-only tools, like Makita, Bosch, Milwaukee or even DeWalt's 12V Max and 36V lines. In order to make the best use of the battery technology and build in a bit more future-proofing, the power control in the tool and the cell protection in the pack have to communicate with each other. This is why most true LiIon systems have several connector pins on the battery and the tool. The 18V line uses only the two battery connection and that is it. The third terminal is a temp sensor in the pack used by the charger in the NiCD line, and a more sophisticated monitoring pin used by the LiIon charging system, which is why the NiCd chargers are not "forward compatible". The new yellow LiIon chargers work with the NiCDs though.
DeWalt has a chance to unify and future-proof the new tool lineup by changing the pack formats as well as the tools themselves. It's reported that the 20V Max chargers will support the current 12V Max and upcoming "14.4" LiIon tools. By doing so, they will have to completely abandon the current pod-and-stem battery pack design that is about 20 years old now, and a throwback to the earlier B&D Professional 7.2-13.2V NiCd setups. The tools themselves can be lighter, the packs smaller and more useful energy can be gotten from the packs. By more closely monitoring the charge levels, much like laptops do, the charge can be metered and excessive discharge and overcharge avoided.
I just hope DeWalt does not pull support for the older lines too soon, I have close to two dozen 18V tools, a few 14.4 and 36V tools, and the early B&D Pro stuff, and they have been awesome performers all. The B&D "Univolt" line appears to have been finally abandoned in the last couple years, and the tools are sitting idle now as a result.
