Afaik, Watts and VA are figures of power that the device can produce.
You can obtain these figures from the other supply simply enough (volts x amps = VA) and they actually work out a lot higher.
However, these figures only show what the unit is capable of producing - NOT what it will put out continuously.
Hence, if you connect a drill that only needs 2.55VA to a charger thats capable of supplying much more the drill will simply take what it needs.

By this logic I should imagine it'll be fine.
I'm not sure on the affect of using a 12v supply as opposed to an 11.6v supply but I should imagine such a small difference wouldnt hurt.

Dont take my word for this though.