Gianni,
The 2.8" NanoVNA usually is delivered with a 400-450 mAh LiON battery which yields about 2 - 3 hours of portable operation. If you have an unused cell phone you can take the battery out of it. The battery input for some NanoVNA's is connectorized, on others it is soldered. The newer NanoVNA-H v3.4 even has a 650 mAH battery so you can go bigger if you want for longer portable operation.
- Herb
