[T-Mobile LG V10 Q&A, Help & Troubleshooting] AnonVendetta:
OK, so I'm going to be upfront about this. I'm using the Zerolemon extended battery, not the stock battery. The phone isn't dead, it does boot up and I can get into recovery, fastboot, download mode, etc. But when I boot up the phone, I sometimes get an "Invalid battery, shutting down" message after about 20 to 30 seconds. I'm currently running stock rooted MM 20J. I've gotten this error multiple times before when I was running Lollipop, much less so on MM. It didn't start getting bad until about a week or so ago. And seems to be getting worse. But that's not the biggest issue.

Now, for the 2nd time in a few days (and never encountered before this), where it is supposed to show a normal charging icon on the charging screen (when the phone is turned off and plugged in), instead it shows something that definitely isn't normal. I've gotten the invalid battery numerous times, but never this. I tried taking a pic with another device, but the pics came out blurry, static-filled, and smudged with fingerprints. So I'll just describe it:

It is a pic of 2 batteries side by side, the one on the left has a ? in the middle and a red flashing slash going through the middle of it. The one on the right looks normal, says LG in the middle. Both sides also say to refer to user's guide. Either way, it's not good.

Sometimes the percent of battery left will change wildly, more than a few times Android has said it is at X percent, then suddenly it's a lot lower in the span of a few seconds to a few minutes. I'm talking drops in the double digits. Ocassionally the value displayed will be higher than before. The "invalid battery" seems to happenly frequently thereafter, until I plug in for a few hours to get to 100%, then I don't see it again for most of the day.

I've had (this) phone for only a few months. When I bought the first v10 about 6 months ago, it initially came with Lollipop. I had to exchange that device a short while later in a T-Mo store, in exchange for another v10 also running LP. Well, that one had issues too, so a short time later I brought it back into the store again and exchanged for the v10 I currently have now, which already had MM. 3 identical phones in 6 months is just ridiculous. And I was able to do all this without using insurance (even though I do have insurance if I ever need to use it).

I do still have the stock battery, I suppose I can use it for now. I've had the Zerolemon itself since I bought the first v10, almost 6 months. I do believe it has a 6 month warranty if I'm not mistaken, which is almost over, maybe I can get it replaced. But I tried contacting their support a few months ago to see about an exchange, they never contacted me. I tried again after that. Still no response. I cant afford to replace it just yet, either via exchange or buying a new one, but will do so (the latter) if it comes down to it. I read somewhere that the "invalid battery" comes from the battery not being seated properly, or the gold/copper contacts being dirty, I've tried reseating as well as cleaning them, no luck. I have no idea what might be causing the error message on the charging screen, my best guess is that the battery is defective or worn out.

I also have 2 original LG fast charger cables/bricks, I've been having trouble using either cable to copy files to/from my PC, it sometimes will just disconnect for no reason (never while flashing, but I don't trust it). I'm beginning to think that the cables/bricks might be bad, or worse, that the phone's charging port is bad. I'm hoping not because I might as well throw it in the trash if the latter is the case.

Not sure what to do at this point, but this is getting to be a big headache.

Edit: Forgot to say but I've never gotten any of these issues with the stock battery.