My DSi flashes both screens for a split second, then shuts off

ok so (deep breath)

2 years ago, i bought a pre-owned blue dsi. it worked just fine, but last week i was on flipnote studio late in the night and i was very tired. so i made the ever-so-wise decision to just leave it on overnight, because as we all know leaving a dsi on overnight with its charger on is a good decision. anyway, next morning i wake up to find my dsi off. 'strange,' i thought. 'i don't remember ever turning it off.' so then i tried turning it on and it flashed for a split second, then shut down. i was like, 'ok, maybe my charger fell out overnight or something,' so i decided to charge it. it only charged for maybe a few minutes before stopping. 'that's strange,' i said. 'shouldn't it have stayed on for longer than that?' so i tried turning it on again. no such luck. i went online and read that it could be the power board causing this, but i'm not sure i have the right tools to go investigate, as i've only gotten the battery casing off at this point. i'm not sure what to do now, so if anyone could help, that'd be awesome.

(tl;dr left dsi on overnight, next morning flashed screens and didn't turn on)