No power to anything please help

[Stuttgart70]

I’ll start by saying I am not too technical. I have a 2003 Boxster S. Didn’t drive for about 3 weeks battery dead. Tried powering to red fuse no luck. Used a 12v, 6 amp battery charger in cigarette lighter. Charger indicated it was charging for about 6 hours now it says it is in “maintaining mode” meaning the trickle charge.

When I turn the key I get nothing. No alarm, do dash lights, no trunk opening. About 30 min into the initial charging I turned the key and the dash lights came on for about 5 seconds. Could I have blown a fuse?

Thanks in advance.