There’s a wide voltage difference between “I’m dead, charge me” and “I’m so dead any half competent charging circuitry will refuse to charge me lest I combust”.

If it’s fuggered, you’ve got nothing to lose by opening it up and seeing how hard replacing the (probably 18650 Li-Ion) cell(s).

Good chance they’ve got solder tabs spot welded onto the cells, but that’s not a showstopper, you can buy em that way if you don’t know anyone with a spot welder.