I do not have to take my battery else, BMW has a nice plug I can just connect to, so when I am ready to ride again, I just pull the plug and back out, no need to remove the seat or anything. It is pricier then the battery tenders you can get at Canadian tire, but the convince and ease of use is worth it for me.
Just run the bike to charge the batt, I ride S1000rr no issues so far since last year. Selling it after summer for 899 panigale though.