I would like to use the Sunsdr2 Pro as a portable device. The optimal supply voltage is stated to be 15 V ... it would be advisable to power the device with a four-cell Li-pol battery, etc., but their voltage without load can be up to 16.8 V, which is 0.8 V above the 12-16 V limit. Is there a risk of damage to the device? How do you power this portable device?

Hello,
16.8V voltage is too high and NOT recommended, it can burn the SS2PRO supply chain.
You can try removing one cell to get 12.6V, this way you'll be able to work in RX mode and with lower output power in TX mode.