I prefer units, such as the (tr)uSDX, which does not have a built-in battery. ?That allows me to plug in batteries of varying voltages to safely check the SWR of portable antennas (or operate QRPp at even lower power levels), by using 6 to 8 Volt battery packs (or recycling a 9V one that a smoke detector had discharged to 7V). ?Then I switch to a higher voltage battery pack only if the antenna shows a good SWR.
73, Ron, n6ywu
