Starting problem. Hope someone can help.

2006 Prius. Replaced 12 V battery 3 years ago, after a red triangle, transmission error event.

So, I started getting the red triangle display again, a week ago, Tried denial, it would start after maybe the third try, And, of course the morning came when that wretched red triangle and scary prompt would not go away and the car wouldn't start.

Came onto chat and got the directions for battery diagnosis, ran the diagnostic, looked at the numbers, realized I had no clue what they meant, shut off the car and tried to start it . Bingo...worked, drove it for a couple of hours. The next day it ran like a top, and the next etc...until I needed to drive somewhere really important last night and, of course, the dreaded red triangle appears. Would not start period. A neighbor tried to jump it and I watched the diagnostics... Stupidly I didn't write the numbers down, but I remember looking at my reference sheet, and thinking the starting #, charging # and drop # were the low side of normal. But it wouldn't start.

I think the problem started last week, from my running the AC mode for 20 mins., not knowing at the time, how damaging that is to the battery. Presently, the car is @ 100 ft from a electric outlet. I don't have a charger, but I'm ready to go get one. I'd like confirmation that there is a good chance I can fix this if I get the right trickle charge on the front battery charge spot. And, I want to make sure I don't screw this up. Questions:

~~~ Is there a portable (non-corded) charger that would bring the 12V back up to a healthy level?
~~~ Specifics as to Brand, V, Amps, Trickle charge, etc, for what type of battery would really help.
Cost is also a serious criteria.
~~~ If I have to use a corded charger, would a charger still work on 100' of extension cord?
~~~~Any other suggestions?

I very much appreciate any help and or suggestions.

Thank You

Marie

 

Thank you Bisco

 

Thank you Patrick. Appreciate it