The X6100 works best with al voltage around 10 Volt. Higher voltages just mean more waste heat development inside the rig.
I
f you are considering to use an external battery IMHO best is to build or buy a LiFePo4 batterypack in 3S (not 4S) configuration. Such a pack will deliver 10 V nominal, which is excellent for the X6100. Hopes this helps.
--
Robert
