Yes—storing a battery in an unplugged charger is generally safe, but it may slowly drain the battery depending on the charger’s circuitry. Some chargers draw a small amount from the battery even when unplugged, so charge loss over time is possible.

If you only want to use the charger as a holder, avoid contact between the battery and charger terminals. Simple ways to do that are inserting the battery reversed if the design allows, or placing a small piece of paper between the contacts.

For longer storage, keep an eye on charge level. Lithium-ion batteries shouldn’t be left fully depleted for extended periods; avoid letting them get too low. If you have multiple batteries, rotating their use is a good idea.