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BMS and phone battery capacity

Hi all,

Context: I have some broken phones and some phones with a worn out battery. So instead of buying a new battery, I decide to scavenge the battery from those broken phones by doing some battery mods.

My question: If I transplant a "healthy" battery cell to a BMS from a very worn out battery, will the BMS record the new capacity after several charge and discharge cycles? or the BMS will keep only the "worst" battery capacity in its memory regardless the real capacity from a new battery cell?

thanks

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Well, you're covering a lot of territory by saying "Apple iPhone", but in general what you'll see is the health information from the old battery. There are tools available that can reprogram the battery information such as the QianLi iCopy or the JC V1SE. Those are the two most popular, but you'll spend a bit for them; there are other devices as cheap as $35 USD available as well.

Note that this only helps you up until the iPhone 11. That's the point at which they changed the way the battery health and cycle count is stored, and those programmers won't work directly on the battery any longer. You end up having to get something called a tag-on flex that plugs in between the phone and the battery and is permanently installed in the phone. That device allows you to access the health information the way you used to and lets the programming device work again, although I have noted that there are now tag-on flex cables available that come preprogrammed to 100% health and zero cycle counts.

You should also note that for every phone after the iPhone XS & XR, you have to keep the original BMS or you'll get the "genuine parts" warning regarding the battery and will lose the ability to view the battery health information. So if you're going into the business of replacing iPhone batteries, get used to swapping out the BMS for all of the newer models.

Oh, and finally, you may want to seriously consider getting a spot welder; heat is the mortal enemy of lithium batteries and the spot welder generates far less heat than a soldering iron.

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Hi Jerry,

Thanks for your helps. For myself, I don't care about the "battery health" in the Iphone. I use Imazing to find out the real capacity of the battery. The problem I have now is after the transplantation, the phone is still shutting down at 3.7 volt as if it still thinks it has an worn out battery. Normally, a new phone with a new battery shutdown only when the voltage is near 3.4V, So I'm asking myself is there a way to "tell" the BMS or the phone that there is new battery cell with much higher capacity, so they can now shutdown with lower voltage.

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