Streamlight now offers 18650 batteries for their products that accept them. Charge your batteries - one or two at a time - in the dual input charging cradle. It uses either USB or "traditional" AC/DC power sources for a wide variety of battery charging options.

Specifications and Features:
Streamlight 18650 Charger Kit
Capable of charging a single 18650 battery or two simultaneously
Dual input: accepts either 5V micro-USB or Streamlight “traditional” AC or 12V DC power sources
Micro-USB input with custom locking feature charges from Streamlight AC/USB adapters or most other USB sources
Impact-resistant polymer construction
18650 button-top lithium ion battery on-board safety control circuit; rechargeable up to 500 times
Single bay charge time: 3.5 hours (either bay)
Both bays charge time: 3.5 hours left bay (priority) and 6.5 hours right bay
Individual bay LEDs for battery charge status
Charger: 4.5 in and 2.4 oz
Battery: 2.75 in and 1.7 oz
Use with Streamlight products that accept 18650 batteries, including the ProTac HL USB and ProTac HL 4
Includes 2x 18650 Lithium Batteries