for the Vim ?
VIM doesn’t support battery management, what you mean that suitable battery holder?
Maybe he speaks of an RTC battery.
If so, maybe an RTC battery with leads and connector will do. Just cover the cell in heat-shrink tubing should be adequate. No mount required.
If I don’t have a battery, when is the clock synced in Android/Ubuntu/LibreELEC? Every time I connect to the network?
Indeed it’s first time your connect to the network, the time will keep running by RTC chip built-in VIM until you plug-out the USB-C power supply.
And the RTC battery slot is designed for the power supply dropping off in some cases. And we designed this for products like Digital Signage which need always keep the time updated, and in the power dropping off case, the time can also keep running.
Check VIM Schematic for further information.