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Repair information and guides for the iPhone 8 that was released on September 22, 2017. Model: A1863, A1905

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Battery draining overnight when powered off

Hi,

I've bought an iPhone 8 with a dead battery and a slightly water-damaged home button. I've replaced the battery with an iFixit battery, and a home button off eBay. Everything on the phone is now working perfectly fine, apart from the fact that it drains its battery from 100% to 0% in a few hours when it's powered off.

I suspected a (partial) short or something similar, so I powered it down, took it back apart and let the logic board cool down. I then took a photo with my thermal camera and one of the display flex cables is staying noticeably warm even when the phone is turned off:

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This only goes away when I disconnect the battery. There is no corrosion anywhere on the logic board, I've re-seated the FPC connectors, and checked that all pins on the connector are clean and straight. I also don't see any knocked-off capacitors or something like this.

Could that heat be the current draw that is draining my battery, and what could be the root cause of this?

Thanks in advance

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From what I've seen hanging around here on iFixit for some time now, it seems that the two things that get affected the worst by water damage are the screen and the battery. Given that you're seeing weird behavior associated with the screen plus the fact that you know there's been previous water damage, I would suggest that replacing the screen might be the next step. If it was me, I'd probably take the opportunity to swap out the battery at the same time.

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@oldturkey03 You're absolutely right; I spaced out on that. No, at this point I wouldn't bother doing anything with the battery until I had confirmed whether a replacement screen fixed the problem or not. If the old battery is still around, it might be worth taking a couple of minutes to swap it back in and see if that affects the problem in any way.

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@dadibrokeit happens a lot to me :-) deleted :-)

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Thanks, but I have already replaced the battery with a new one from iFixit, because the old one was swollen. However, a new screen would cost me more than the phone did, so I don't think that's worth it for me

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@twometer Really? Of course it depends where you get it from, but to me a $14 replacement screen from Amazon would be worth a try.

https://www.amazon.com/Replacement-Digit...

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Oh, that would definitely be worth a try. I was looking at the $70 screen from the iFixit store 😅

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While this doesn't really address the root of the issue, you can try completely shutting down the phone (hold the power button, slide the slider). I had an iPhone 5 a while back that would drain to 0% while I was in school, but once I started shutting it down in the morning, it would only drain to ~80%.

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The problem actually occurs when it is shut down completely, so that's not it. I did the shutdown procedure, but it still uses up power as if it was turned on.

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@twometer Ok, now *that* is weird. Maybe the battery is discharging for some reason?

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@shingle it seems like it is. I thought maybe it comes from the screen flex cable which stays warm after shutdown.

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Twometer will be eternally grateful.
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