help/clarity on battery upgrade, battery calibration, and need for a custom rom

[taco.tuesday]

Hi! So the original battery in my AT&T Galaxy S6 Edge Plus has been showing some erratic behavior lately like massive drops in battery % out of nowhere. For example, one of my alarms went off and battery was at 98%. Around 5 minutes later I press the home button to check the time and the battery was at 15%. I rebooted the phone, battery was at 4%. I don't notice any bulging or separation when inspecting the back glass but I'm certain the battery has reached it's final days. I've been reading about replacing it myself, and found out you can actually upgrade the battery. I've read several posts from people who have successful replace their S6* battery with a higher capacity S7* battery. Unfortunately some specific details have been lacking or conflicting so hopefully the wealth of knowledge in this forum can provide some clarity on a number of questions I have..

- I've read the S7 Edge 3600 mAh battery fits perfectly in place of the S6 Edge Plus 3000 mAh battery, so there's no gap issues with the back glass when the phone is reassembled. Is this true?

- I've read that the S6 Edge Plus firmware has a hardcoded battery size of 3000 mAh which interferes with the `battery calibration`. Is this true? If yes, what does that actually mean? It won't fully use/charge the battery? It won't report the correct % of battery left?

- I've read about a "KIBOI Kernel" made for the S6 with an S7 Edge battery installed that properly calibrates and reports battery %. Would this kernel work for the S6 Edge Plus as well, or would I need a kernel/firmware specifically for the S6 Edge Plus?

- I've read you can modify the stock S6 Edge Plus firmware 3000 mAh value to the S7 Edge 3600 mAh, flash the slightly modified stock firmware, and calibration/battery % will be correct. Is that true? If yes, can I also remove/uninstall the crapware AT&T pre-installs and other apps I don't want pre-installed like Facebook, Twitter, Google Hangouts, Amazon Kindle, etc etc etc etc.?

- Is wireless and/or wired charging affected at all by using the S7 Edge battery in the S6 Edge Plus?

- I've seen there are S7 Edge battery upgrades to higher capacities, for example 4000 mAh while maintaining the same physical size. Any advice on going with on of those rather than the stock 3600 mAh S7 Edge battery capacity?

Specifically, my phone is an unlocked AT&T Samsung Galaxy S6 Edge Plus (G928A), not rooted, running Android 7.0, security patch level Aug. 1 2018, baseband version G928AUCS6ERH1. I switched from AT&T to Straight Talk for my provider a couple years ago, if that matters at all. I got the phone, new, locked & under contract with AT&T when it first came out.

Thanks for any and all help!

 

[taco.tuesday]

Unfortunately I'm the first one to reply in this thread so I guess nobody was able to offer any clarity on anything I asked.. I wound up moving forward and here's what I learned...

I wound up buying a 3800 mAh battery that was supposed to be the same size as the stock S7 Edge battery. It turned out to be slightly thicker, which caused a slight gap on the battery side of the back glass. I use an Otterbox case which fits really snug around the phone so I just press the back glass on as best I could and shoved it back into the case.

People aren't kidding when t hey say the sticky tape that holds the S6 Edge Plus is super-mega-ultra adhesive. I couldn't get the back glass to budget heating it with a hair dryer so I wound up using a 300W heatgun moving back & forth on the volume buttons side. Once I got the side up a little and a tool wedged in there I heated around all the edges for about 20 seconds. Getting the back glass to lift up was a piece of cake at that point, UNTIL I got to about the last 1/2", which happened to be a corner. I should have applied more heat to make sure the glue stayed workable but I thought since I was so close to having it off, I had it in the bag. Nope! I wound up cracking it and needing to buy replacement back glass. The lessons here are 1) it takes a lot of heat to get that tape to loosen up 2) It takes a little muscle to get the back to first lift up, 3) I'd recommend not pushing your luck trying to get the back off in one go if you're new to this. Instead I'd say get it about half off, then re-heat the remaining half.

Android 7.0 reports my new battery at 3000 mAh so that's just a hardcoded value. I've tried to calibrate as best I could while still using the stock os. The closest I've gotten the battery display is showing 97% when it's actually 100%. I have no clue how accurate the battery % display is across the full range. I expect not hugely off but maybe in the ball park enough to have at least a rough idea. That's purely speculation though. After 8 hours of idling + about 5 text messages, the battery went from 97% to 84%. Again, I'm not sure if that's reliable at all.

It cost me about $25, which is roughly half of what my local repair shops wanted to replace the battery with another 3000 mAh one.