Battery plummets at 20%

[lontano]

Has anyone else observed a sudden drop-off in the battery indicator as you near 20% charge or so? I usually don't let my charge get that low, but twice now I've watched as it depletes rapidly to zero. I just watched the numbers tick down before my eyes over maybe 10 minutes until it powered itself down. Once plugged in, it showed zero charge. I don't think it can be explained by unusual app activity. I'd appreciate any insight you can offer.

 

[Mooncatt]

Electronics require a certain amount of wattage to run, which is voltage X amperage. As the voltage in your battery drops during use, the current has to increase to offset it. That sets up an almost vicious cycle that drains the battery quicker as voltage continues to drop. It's not like the tank in your car that runs normally until it flat runs out of gas.

 

[lontano]

That makes perfect sense! Thanks!

But do other manufacturers scale or calibrate their battery indicators to compensate for this effect? I was receiving estimates of over an hour of remaining charge right before shutdown. Is this typical behavior that I just haven't noticed until now?

 

[Mooncatt]

I'm not sure if any manufacturers do that or not (and I'm not going to test my phone due to the damage it can cause by going under 20-25%. Battery meters in phones are based on voltage, so I'm not sure if that's even possible. It may, but would require extra testing to work out the calculations, and even then it would just be a generalization. Every battery is going to handle that sort of discharge differently. I personally don't think it's worth it.

 

[Rukbat]

Once plugged in, it showed zero charge.

To me, that says "dendrite" (see Lithium Battery Dendrite links if you're interested). Since it happens at 20%, and you shouldn't let the battery go below 40%, you can get away with keeping the battery. Or you can have it replaced. (But dropping it to 20% or lower too often will kill [as in "can no longer hold a charge"] the battery quickly.)

 

[lontano]

Thanks for your replies!

 

[lontano]

I'm following up on this with Samsung support. I'll let you know how it resolves.

 

[lontano]

Hello again.

As promised I'll report how this problem was resolved in case anyone experiences something similar with their S9.

Samsung support asked me to take it to a local affiliate repair shop for assessment. They just plug the phone into their diagnostic device and report back pass/fail on a series of test. My battery passed so there was nothing more for them to do.

Samsung did not dismiss my concerns. They sent me a shipping label and I sent the phone to their repair facility in Texas. They repaired some cosmetic issues that I hadn't asked them to repair - a cracked corner of my front glass and a scraped frame. They were going to charge me for it but I asked them not to do the work since it wasn't necessary from my perspective. I was told that they don't want to send out a phone to a customer looking like that. I'll just say that the issue was resolved to my satisfaction and now the phone looks as good as new.

Regarding the battery, no repairs were listed to address it. I tested the phone at a low charge and there was no longer a problem with apparent rapid discharge. I use the app AccuBattery, which I've used since Day 1 to preserve the battery's capacity. Before the repair, it showed 103% capacity. Now it's showing 92%. Granted, that will probably change since that's based on only seven charging sessions.

Did they replace the battery? If so, did they install a new one? Or did they recalibrate it in some way? I can't say, but they did something.

Thanks for the commenters above for their advice and input.

 

[NWJA]

I had the exact same issue as you and since I kept my phone between 30 to 80% I didn't realize this issue was happening.. I tried several different charging methods with no avail until it happened again and I charged the phone from the usb 2.0 port on my computer, so it got a low 0.5A charge, all the way to full.

Ever since I've done this I have not had any issues and I've charged it many times with the supplied charger, with fast charge turned off and on.

Hope this helps anyone else having this issue.

 

[lontano]

Wow, very strange. Good info, thanks!