I have a refurbished Galaxy S3. Sometimes it charges to 100% while powered off, but reports 51% as soon as I start it up. Lately, it goes down to 50% or lower even right after charging.

I haven't installed many apps or used the phone extensively yet.

I find lots of links for determining battery drain, but nothing so far on how to tell if I need a new battery.

I'd like to be relatively sure it's a bad battery before replacing it.


I have eliminated the problem, but have no idea why what I did worked ;(

1) I bought an inexpensive charging-only cable. Using this, the phone charges very nicely.

2) I turned on Power Saving.

3) I bought a more expensive version of the battery.

Now the phone charges fully, lasts a long time, and keeps the charge when turned off.

None of this makes sense - especially the fact that it used to drain when turned off (not suspended). Changing the cable shouldn't have done much either because the old cable did charge the phone - or at least - the phone said it did.

  • I had a similar galaxy phone. I noticed that the battery had bulged out a little. And a few days later it grew enormous and I got a replacement. Is there a bulge on yours?
    – NVZ
    May 1, 2016 at 20:22
  • No. It looks fine. I ordered a couple of spare batteries anyway (and an external charger.)
    – Joe
    May 3, 2016 at 6:48
  • Just one, and maybe two, tops, is all you need.
    – NVZ
    May 3, 2016 at 7:23

2 Answers 2


Li Ion or Li Po batteries don't die suddenly - their performance degrades in terms of :

a) Short Term: Ability to hold charge and deliver expected performance

b) Long Term:: Deliver upto 80% capacity upon being charged / discharged over a period of time (in other words life of battery). The battery is considered to be technically dead if it delivers less

There is no sure way of determining and saying this battery has gone bad, but there are a couple of things you could try:

  • Spin Test: Since your phone has user removable battery try this. For details, see this nice answer with embedded video.

  • Vbatt: This app should give a fairly good indication, since it simulates discharging under screen on condition . When you charge your battery to 100% (irrespective of the reading it shows on disconnecting ), activate this app widget and it will tell you the voltage level and how long it should last under screen on condition. Let it ruin till the battery nearly runs out and compare the predicted Vs actual. Simple. From app description

  • Vbatt is a simple battery widget for Android smartphones and tablets. It displays the current battery voltage (Vbatt) and the remaining battery capacity (percentage) and optionally logs these values to a CSV-file.

  • The main reason for developing Vbatt was the differing behaviour of replacement batteries while discharging them in daily use ... For a better estimation of the remaining phone runtime the Vbatt widget displays in addition to the remaining capacity (percentage) the battery voltage

While battery voltage is arguably not the best indicator of health of battery, running this app can help you in a couple of ways

a) Giving you the current performance which you can compare with earlier performance as you recall or from Screen On Time (SoT) which you can gather from internet or forums

b) If you can lay your hands on a new or properly performing battery from your friends, running this app on both batteries, you can easily judge for yourself. You can even ask your friend having the same phone to install this app, run it and compare.

Since your phone is refurbished, there could be another factor at play for deterioration in performance- date of manufacture of battery. Li Ion batteries (for that matter all batteries) suffer from Self Discharge At the rate of 4% every month, which means if your battery, even if it is original, but kept on the store shelf for say an year before being sold, it had already affected the longevity of battery and it shows up in performance

IMO, looking at the battery figures shared, I would recommend battery replacement (assuming no other reason like hardware issues). It would help you to decide by running tests mentioned

  • After I use the provided info, I expect to accept this answer. Followup: How long might it take for vbatt to get it to 5%. I'm not sure I want to let it go to zero. Wouldn't that hurt the battery? I know you can't answer precisely. I just want to plan how long I have to babysit the process. I just ordered 2 spare batteries and a charger anyway. That video of the spinning battery was funny. That's a new diagnostic method<g>.
    – Joe
    May 3, 2016 at 7:12
  • You are right on not letting the battery go below 5%, I would even say 10% but didn't stress that since your battery seemed to be a goner anyway. I am guessing it should take less than 4 hours but you can surely make a reasonable estimate if you can't stay that long. Yes, the battery sounds because of the bulge. It isn't new. You will find you tube videos Did yours spin? Mind you, this is a good indicator most of the times. I had a spinning battery that lasted me a few months. Vbatt app methods is hardly mentioned .it hit play store in ' 14. All the best
    – beeshyams
    May 3, 2016 at 8:09
  • wondering if you did the test?
    – beeshyams
    May 19, 2016 at 14:24
  • I tried the Vbatt app and watched it drain the battery. I did not know how to use the information it gave me any further than that. See forthcoming update to my question for more details.
    – Joe
    Jan 4, 2017 at 20:28
  • You now have performance of your bad battery with the time taken to drain From a certain level. Now this test needs to be repeated with a good or new battery to compare. If you the read app description, it stresses the replacement battery performs as mentioned in second bullet point in the answer
    – beeshyams
    Jan 5, 2017 at 3:17

It could be a bad calibration of the battery.

Charge your phone to 100% and then use it as normal, without charging. Eventually you'll hit 0% and your phone will turn itself off. Then without turning it back on, charge it until 100%. That can often reset the calibration.

Also take note of how long your battery is lasting. If you're not a heavy user you should easily get a day out of a good battery. If your getting to 0% before the end of the day your battery might be on it's way out. My samsung battery was going from 100% to 30% in an hour and then draining quickly. A couple days after getting those symptoms it just died.

  • 2
    Note: Running down to 0% is poison for LiIo (and also LiPo) batteries, it shortens their life times. I'd take 5% as lowest limit. But as usually the battery doesN#t last as long as the day with smartphones, just a full, uninterrupted charge at that point would do for calibration – so most users calibrate daily without knowing it :)
    – Izzy
    May 1, 2016 at 11:19
  • @Izzy I've read similar conclusions, but I'm having trouble finding credible references to verify it. Do you have any good references for those conclusions? May 1, 2016 at 11:46
  • @RockPaperLizard Have you checked with our charging tag wiki yet? :)
    – Izzy
    May 1, 2016 at 14:02
  • 1
    @Izzy Even though I sometimes write the wikis, I often forget to check them. Thanks Izzy. May 1, 2016 at 19:54

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