For the purpose of the Detect Magic and Identify spells, is a magic item that is currently out of power still treated as a magic item?

Question

If a magic item runs on "Magic Batteries", when the item is out of power, would it be treated as a magic item for the purpose of the identify and detect magic spells?

For example, I have a mirror that shows through illusions. It has crystals around it that are destroyed as you used it; you can replace the crystals for more uses when it has no crystals. Would it still be treated as a magic item that is detectable by the identify/detect magic spells?

Would the same be true for items with charges that recharge at dawn? If the item has 0 charges and is not dawn yet, would it be still be treated as a magic item?

Answer 1

Yes, it is still magical

On the basis that things do only what they say, a magical item remains magical unless there is a rule stating otherwise.

The rules call out several cases where magic items do lose their magic. Here's a sampling (all citations from Dungeon Master's Guide):

Once used, a consumable item loses its magic. (pg. 141)

Once it hits a target, the ammunition is no longer magical. (pg. 150)

Once an arrow of slaying deals its extra damage to a creature, it becomes a nonmagical arrow. (pg. 152)

Doing so ends that pellet's magic. (pg. 166)

If a magic bead is removed from the necklace, that bead loses its magic. (pg. 182)

On a 1, the staff becomes a nonmagical quarterstaff. (pg. 201)

However, many items that can regain their abilities do not include this wording:

The bowl can't be used this way again until the next dawn. (p.g 156)

The cube starts with 36 charges, and it regains 1d20 expended charges daily at dawn. [...] If the cube has insufficient charges remaining, nothing happens. (pg. 156–160)

On a 1, the staff retains its +2 bonus to attack and damage roll but loses all other properties. On a 20, the staff regains 1d8 + 2 charges. (pg. 202)

Many items also call out circumstances under which they are destroyed, in which case there is no longer an item to be magical.

It sounds like your mirror is a homebrew item, in which case the DM is welcome to add a rule stating that the item is nonmagical when without crystals, but this would be a specific exception, not a general rule.