I like choice, but I do not like having to choose between a bunch of different chargers – especially for the same brand of cordless tool. But until recently, that's how it was if you owned subcompact (12v) and full-size (18v) tools. It didn't matter if they were the same brand, you still needed two chargers.
But as of a couple of weeks ago, that's no longer the case – provided your tools are DeWalt or Milwaukee.
DeWalt's new charger (DCB103) takes post-style batteries (7.2, 9.6, 14.4, and 18 volts) on the left and slide-mount batteries (12 and 20 Volt MAX) on the right. It will be sold as an accessory ($99) and will be available this April.
The Milwaukee charger (48-59-1812) will accept M12 and M18 batteries. Available in March, it will be included in selected cordless kits and transitioned into more kits throughout the year. It will also be sold as an accessory ($59).
I would like to see a charger that not only charges both platforms but more at once. I have 3 M12 chargers and 4 M18 chargers that are daily in my truck. I need way too many plugs and arms to carry it all onto a job. Make a large charger that can do 4 18's two on each side and three 12's on the end and I'll preorder that on quick.