How can I make the charger be on without the key?

Assuming that this is some form of motor vehicle and that you have the charger plugged into the 'cigar' lighter socket...
This is likely to be a re-wire job to pick up a positive 'always-on' feed. Probably not a good idea on such a recent model, for resale (and possibly, safety) reasons.
I mostly charge my mobile (cell) indoors and just top it up when I'm driving, which works out fine on the BMW, although the socket is 'always-on'.
If this is a permanent installation they may have wired it this way because some linked ICE displays, even in 'background' mode, will flatten the battery if left for more than a couple of days.

Robert Johnson
September 2004