Battery went from 100% to 0% on reboot

[Tim98TA]

I charge my phone, S9, every night and reboot it every morning.
This morning when I rebooted it, it shut down. When I tried to restart it, it would come up part way, then shut off. I plugged it into the charger and it showed 0% battery.
Why would it go from 100% to 0% on a reboot?

 

[Mooncatt]

If it just happened this one time, it could have been a dendrite growing inside that finally shorted out the battery. This would be further suspected if the phone got hot (not just warm, but too hot to touch). During the short circuit, they tend to blow like a fuse and things return to normal again.

If this is an ongoing issue, then the battery could simply be worn out. As batteries age, internal resistance builds up and it causes increased voltage sag when under load. The bootup process is pretty demanding on resources, which could cause this to happen. Other symptoms of this would be random immediate shutdowns at an otherwise normal battery level without going through the regular shutdown process.

But either way, sounds like a battery issue.

 

[Tim98TA]

Hasn't happened but this one time.
Phone wasn't any warmer than it normally is when I take it off of the charger in the morning.

 

[Mooncatt]

Hasn't happened but this one time.
Phone wasn't any warmer than it normally is when I take it off of the charger in the morning.

Gotcha. This one instance isn't much to go on and, for me, falls under the category of "sometimes stuff happens." It's certainly something to keep an eye on because it shouldn't be happening. If it continues doing this, then it would be something to dive into deeper.

I'm still leaning towards a dendrite unless someone else has a better explanation. Those do happen at random and there isn't much you can do about it. Thirty are rare, but continuing to have them would indicate a battery defect and recommended replacement.

 

[missy8787]

Sounds to me like you may need a new battery. Does your battery drain fast during the day? When I had the s9 plus my battery would only last 3 hours and that was with just phone calls and txts.

 

[Tim98TA]

Sounds to me like you may need a new battery. Does your battery drain fast during the day? When I had the s9 plus my battery would only last 3 hours and that was with just phone calls and txts.

Yeah, it's kinda getting to that point. New it was good for almost 2 days. Now maybe 1/2 a day.