2010 prius didn't start. Gradually lost all electrical over 1 1/2 hours with charger attached.

I bought a 2010 prius this past summer. I left it at the airport for 16 days and had to use a jump starter to get it started. I drove it home, adout 45 miles over an hour without a problem. The car sat for 3 1/2 days in 20 something temps.
I initially got a green light on the start button, but nothing seemed to happen. I tried again after around a minute. I went to get a charger. The door was chiming when I got out and it sounded like an electric motor was going for a few seconds. When I got back, the radio was on, but the car was not. I hooked the charger up and the battery looked to have juice left. The arrow was between the 10 and 15. charged it while I read this forum. I went back out. The light was amber, but eventually went to green after repeated break pushes. Still didnt start. The taillights and headlights didnt work. The horn didnt work and I couldnt open the hatch. The interior dome lights were dim. After letting it charge for another hour or so, I came back out and nothing was working. No start button light, no dome light, nothing on the dashboard. A blizzard kicked in so I took the charger off.
This morning I connected the charger directly to the 12 volt. The charger arrow didn't noticeably change from using the under the hood connections. Im currently trickle charging. I didn't notice any codes when the dashboard lights were working, but I wasnt specifically looking for one.
The only dealership is around 45 miles away in Anchorage. Im not mechanical, but I had assumed that I could get a prius started. I was wrong. Any idea what the proplem is. I don't understand whats happening.

 

The battery is charging now., and lights are back. Im guessing, I can start it in the morning. Sorry if i cluttered up the forum

 

Thanks for the responses. The car starts. its miserable day outside, so i havent driven it yet.

Im not sure how old the battery is. probably less than 5 years but more than 2. Ive been leaving the car for weeks at a time. Ive had to jump it once and use a charger 4 times.

I guess I don't understand how chargers work. I had assumed that the needle on the gauge indicated that it was charging, but that wasnt the case and the outlet was dead. I trickle charged all night and the needle barely moved, still between 10 and 15. I followed advice and bumped up the amp rate, but the charger indicated that it was fully charged. Im guessing that means that the battery needs replacing. I don't have a multi meter. I understand that some places do free checks though. I'll probably go to a store that does installation too. Shipping large batteries to alaska tends to be problematic as most places wont ship here.

If anyone is willing to suggest a replacement 12 volt carried by stores, or warn me off of one, id appreciate it. It will surely take a while to get an appointement at the anchorage dealership, but if thats the best choice, I can probably wait a bit.