>Lastly, based on my luddite eyes, the difference between makita, milwaukee, bosch, dewalt and ryobi batteries seem to me to only be a different keying in the plastic mating parts

The fact that you can buy adaptors to allow one brand's batteries to be used on another brand's tools would seem to back up your theory. However, with the adaptors costing around £20 each and being produced by no-brand 'warranty voiding' unofficial third parties you've never heard of, it would be an expensive business if you wanted to be brand agnostic in your power tool choices, as you'd need a heap of adaptors to cover all the various combinations of tool & battery. Added to which is the potential for a dodgy 3rd party adaptor to damage tool or battery.

I'd like to see the EU designate a common battery interface for all newly manufactured tools & batteries. That way we could buy the best tool for the job each time, instead of being locked into using whatever the Blue, Yellow, Red or Green team are fielding in that area.

The manufacturers would doubtless also produce their own adaptors to allow their existing tools & batteries to work with this new 'One Interface to Rule Them All'

+1 that the plastic is the main difference are the "everything to Ryobi"-plastic adadpters you can buy. I use Makita battery->Ryobi tool and it works great.

Of the tools you listed, none are made by the same company. At least for their primary products.

All of the large format packs have pins for each cell, so charging with a standard balance charger is pretty easy. You can find plenty of schematics for homemade controllers online. Where they differ however, are the other pins. Some use a communication protocol like SMBUS. Some have dedicated pins for specific things like overcurrent or temperature. It varies highly from manufacturer to manufacturer.

AFAIK, all tool brands are moving to communication protocols for the packs.

[EDIT] Someone mentioned adapters. I don't believe there are adapters that support newer communicating packs (e.g. the OEM chargers won't work with the adapter). Older packs are all analog, so conversion is just a simple matter of rerouting the pins.