Charging problems

[SwoleCole]

I thought I had this sorted out but I guess not.
My bike needed a jump if it sat for any amount of time when I bought it, so I assumed I needed a new battery. Went ahead and bought an expensive battery and cheap battery tender. It ran fine like this for a couple weeks. Then I tried to leave work one day and it was dead, headlight wouldn't even come on, and for some reason push starting it didnt work. I jumped it from a car and this started it but when I disconnected the jumper cables it died immediately. I can't figure it out, is something drawing on the battery when it's sitting or is it just not charging when running?

Anyways any ideas where, and how, i should start to look?
Thanks in advance...