The InfiRay IBP-2 3.1Ah, 3.6V Lithium Ion battery is the OEM replacement rechargeable battery for the following:
InfiRay Cabin 19 (CBL19)
InfiRay Cabin 25 (CBL25)
Infiray RICO G-Series 640 (GH50)
Infiray RICO G-Series 640 (GH35)
Infiray RICO G-Series 384 (GL35)
Infiray Finder V2 FH35R
IBP-2 Li-ion Rechargeable Battery Pack 3.1Ah/3.6V
Every thermal scope runs on battery power, because the sensor, processor and display all need electricity. The RICO G-Series GH50, GH35 and GL35 use this IBP-2 rechargeable pack, and carrying a charged spare is the simplest way to stay out longer on a cold night.
It depends on the scope. Some take common cells like 18650s or CR123s, while others use a pack made for them. The InfiRay Cabin, RICO G-Series and Finder V2 FH35R listed here take the IBP-2, a 3.1Ah 3.6V lithium-ion pack.