Don't give a legit answer, this is in the EoF.You have to provide more info on this. Does it show a charge light? Pop out the battery for a few minutes and let it sit. I forget if the 3DS can power up at all (even with the charger connected) if the battery is bad but I don't think it will. If the charge light comes on then it may just need a new battery. If the charge light constantly blinks then it is probably the charger that has gone bad. Report back to see if there is anything else you can try.
Weren't you originally going to leave for a long time?Was this originally in the normal 3DS section?