Why are my old iPhones completely dead?

When the iPhone (or any other phone) is stored then the battery runs down to zero. This condition can reduce the Battery Health very fast. A rule of thumb is to never let your battery's charge drop below 20%. FYI - Batteries Health continues to drop with time and it doesn't matter whether the battery is in use or not. I suspect that the battery inside your old iPhone is completely dead. It may or may not salvageable. You can get the devices examined at the Apple Store and determine the cause.

Axel F.

Deadiphones Said:

"Why are my old iPhones completely dead?: I cannot charge anymore or turn them on."

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Humidity and Corrosion:

If your iPhones have batteries and have been sitting there for years on end, then humidity may have gotten to them. That would have made the batteries become corroded.