Lithium-ion batteries have largely replaced Ni-Cad and NiMH batteries in rechargeable dive lights. They store substantial energy in a compact, lightweight pack and have low, but not zero, self-discharge. Actual burn time depends on battery capacity and the light output selected.
For US passenger air travel, check the watt-hour (Wh) rating of each battery pack:
- Up to and including 100 Wh: within the normal lithium-ion battery size limit.
- Over 100 Wh through 160 Wh: larger spare batteries require airline approval, with a maximum of two per passenger. This allowance is not blanket approval for a dive light with its battery installed.
- Over 160 Wh: dive-light batteries cannot travel as passenger baggage.
Carry removed and spare lithium-ion batteries in your cabin baggage, protect the terminals against short circuits, and protect the packs from damage. Remove them if your carry-on bag is checked at the gate. Check your airline for stricter limits. See FAA lithium battery guidance.
Dive lights capable of generating intense heat have additional requirements: FAA guidance calls for airline approval, electrical isolation to prevent activation, and a maximum 100 Wh lithium-ion battery. Completely removing the battery removes the light itself from this hazardous-material restriction; the removed battery still follows the spare-battery rules. See FAA guidance for diving lamps and other heat-producing devices.