Have just sold my 1200GS and have bought a K1600GT... which is very nice. 
My Optimate 4 worked well via the aux socket on the GS but is not so happy with the K16. Tecmate advise switching on the ignition once a week which allows the Optimate to access and start charging the battery via the aux socket. Not sure how long it lasts before the socket is closed down again.
I know the other option is to charge direct to the battery.
Info from Tecmate here.
http://www.tecmate-int.com/ENG/k1600.php
Out of interest what are you K16 owners doing to keep your batteries up to scratch?
My Optimate 4 worked well via the aux socket on the GS but is not so happy with the K16. Tecmate advise switching on the ignition once a week which allows the Optimate to access and start charging the battery via the aux socket. Not sure how long it lasts before the socket is closed down again.

I know the other option is to charge direct to the battery.
Info from Tecmate here.
http://www.tecmate-int.com/ENG/k1600.php
Out of interest what are you K16 owners doing to keep your batteries up to scratch?
