Created attachment 8364 icon size difference The vertex maia battery icons in tray differ in size greatly when laptop is plugged and unplugged from wall power. This only happens when it's added as an item in the panel, it works fine when it's set from the power manager settings (System tray icon) switch. I've tried changing the panel row size (currently at 30), moving around the 16 and 22px battery-charged.svg (and full.svg) icons in all sorts of combinations but couldn't get it to stay in one size. The system is Linux 4.19.30-1 Manjaro x86_64 with arc dark theme, Xfce 4.12
The systray is only there for legacy reasons and to support desktops other than Xfce (in the past also LXDE used to rely on xfce4-powermanager, not sure if that's still the case now that it's Qt-based). Please check if the panel plugin is an alternative for you, we'll probably not spend time investigating systray-related issues.
(Especially if it's a cosmetic and not a functional problem)
With the 4.14 panel you can define a global icon size value for all plugins, including xfce4-power-manager. The trayicon is a different story, you cannot enforce an icon size there properly.