iPhone 7 horrible battery life (logic board issue)

hello The Tech…

this is a misinterpretation, although I admit the observation is impressive (you are predisposed to be a really good apple technician). the effect of the loss of potential while the phone is turned off can only be a short circuit in the electric line. To prove this, you need to connect your motherboard to the workshop power supply, directly through the battery port. Then you will see from the power supply indications whether and how large the short circuit is. If you see only 0.000 it may mean that the short circuit is not in the motherboard but in connected accessories (tape DOCK, cameras etc). I suppose, based on my experience, that one of the comparison resistors has burned out and now has a very low resistance, which would confirm the symptom.

finding the damage, i.e. the entire electronic diagnostics, is the largest part of the repair fee. If you can find it yourself, you will save a lot. All that's left is workshop experience and some equipment. Such a service (desoldering the indicated component and replacing it with a functional one) should not cost more than $ 15-20. If you have these skills yourself, you won't pay anything (the item can cost less than $ 0.5)