My phone died / ran out of battery.
'Scaricato' — sca-ri-CA-to. Stress on the third syllable. 'Mi si è' — the reflexive-passive construction: mee see EH.
Use to explain why you didn't reply to messages, missed calls, or couldn't communicate before the plans. A modern, universally understood explanation.
'Mi si è scaricato il telefono' uses the 'si' passive construction — literally 'the phone discharged itself to me'. This unintentional construction is grammatically elegant and implies the event happened to you rather than by choice.
Avevo il telefono spento.
My phone was off.
Simpler — just states the phone was off, no cause given
Non avevo campo.
I had no signal.
'Campo' (field) = signal — extremely common in Italian mountainous regions
Ho perso il telefono.
I lost my phone.
More dramatic — generates concern and sympathy but hard to sustain as an excuse
In Italy's WhatsApp-dominated communication culture, being unreachable even briefly generates genuine concern. Friends may call multiple times before assuming something is wrong rather than assuming you're simply busy.