If you accidentally let your iPhone die completely and store it at a 0% charge for a week will it permanently damage the battery?

So what’s the best way to store spare iPhones for long term? Just keeping them charged as if I was using them?

Apple recommends you charge the device to at least 50% before storing. Lithium batteries have a long shelf life. If the device is off, it will lose charge very slowly. You can leave your phone for weeks or even months.

Is that guaranteed to cause a problem? No. Is it very likely to cause a problem? I would say yes.

It is best to avoid completely discharging your iPhone's battery to ensure maximum life.

~Lyssa

There’s no point storing them long term. The lithium cell will degrade over time used or not. Lithium cells have a finite useable lifespan and a finite shelf (idle) lifespan. Lithium batteries should be used as soon after manufacturing as possible to get the most use from them.

They will last best if used regularly. The ideally should have partial discharge/charge cycles often.

Over the very long term, the worst thing you could do would be leave it sitting idle. In a year or so, it will be useless if left idle the whole time.

If you‘re only storing it for a week or so, ideally leave it approx. 40-60% charged.

And an associated question; can we leave it on the charger always?

When we had iPads for student use, we fully charged them, then powered them off before storing them for the 2-3 months that the students didn't need them. That seemed to do the job just fine.

~Lyssa