Fiddler, it depends on brand and model number. For instance the most recent Flir thermal rifle scopes are the Flir PTS series. They have an option for CR123 batteries which is fairly standard. However, I hunt very cold temps in ND and I don't want to be messing with changing batteries multiple times per night, so you can either buy a
Battery Pack System from a company like night goggles, or you can buy cables, and a battery pack and try to make your own. With a pack like this, you are looking at probably 2 full nights of hunting and you just charge it when you are done hunting.
Some thermals such as the Pulsar Trail, Helion, and Thermion series have their own rechargeable battery packs that come with the scope. They are integrated right into the device vs having to secure the battery elsewhere. You can charge the packs connected or disconnected from the thermal. Integrated battery packs are very nice, however, some people worry about the potential issue if they are no longer made. This doesn't concern me but it is a concern for some.
To answer your questions, many thermals take CR123 batteries, and they would be useable in any thermal that takes CR123s. If you are using a battery pack (just like used to charge a smartphone), as long as the scope allows a 5V power input, it will probably work with many scopes but may require a different USB connector. If the scope has a proprietary battery, it would only work with that Brand and potentially that model. The answer is not cut and dry and depends on many factors. I hope this helped.
