A collection of the four seemingly most compatible methods from this page. The first one's really quite genius. Tested from XP up. Confusing though that there is no standard command available to check for admin rights. I guess they're simply focusing on PowerShell now, which is really useless for most of my own work.
I called the batch 'exit-if-not-admin.cmd' which can be called from other batches to make sure they don't continue execution if the required admin rights are not given.
rem Sun May 03, 2020
rem Methods for XP+ used herein based on:
rem https://stackoverflow.com/questions/4051883/batch-script-how-to-check-for-admin-rights
goto method1
:method1
setlocal enabledelayedexpansion
set "dv==::"
if defined !dv! goto notadmin
goto admin
:method2
call fsutil dirty query %SystemDrive% >nul
if %ERRORLEVEL%==0 goto admin
goto notadmin
:method3
net session >nul 2>&1
if %ERRORLEVEL%==0 goto admin
goto notadmin
:method4
fltmc >nul 2>&1 && goto admin
goto notadmin
:admin
echo Administrator rights detected
goto end
:notadmin
echo ERROR: This batch must be run with Administrator privileges
pause
exit /b
goto end
:end```