How much current should a car draw from a battery when it is off?
That’s far too much current and will possibly kill the battery after extended unused periods and a voltage drops below 11.5V when sulphating accelerates.

a fresh 50Ah battery may be dead after 100h @ 0.5h rate.

Reduce that to &lt;50mA or add a trickle charger and plug in it if you cannot locate or eliminate the TDB load.