When the fullRepresentation is used directly in a very wide panel,especially if other widgets are also present, Plasma may freeze as itgets stuck on switching between the representations - thecompactRepresentation is large enough that it wants to switch, but thefullRepresentation ends up too small and switches back, forever.
Unsetting Layout minimum sizes (and preferredHeight) in those casesprevents the issue from happening. This yields a square size which isn'tnecessarily optimal for battery monitor with possibly lots of entries,but better than a total freeze and is a reasonable and predictabledefault size for in-panel use.
See also kdeplasma-addons!851 and a bunch of other recent MRs