Odd battery issue 4S

[roanmy]

So I bought a used 4S and I never expected the battery to be great, but it's acting really weird. It shuts itself down sometimes when it's under 41%, mostly while trying to open snapchat or something smilier, but also while watching Netflix. Then it says it's out of battery, but when I plug it in and it turns on, it has the same percentage as when it shut down.
Also, at one point it had 25%, then I plugged the AC in and it said 31% right away. After I unplugged it again, it went down to 21%.

My main question is, does this sound like the battery would be replaced, a software issue or something else entirely?

 

[Technarchy]

First things first, have you done a factory restore?

 

[Broadus]

It sounds like the battery needs replacing to me. I bought my 4S in October 2011, and I just replaced the battery for the second time.

 

[roanmy]

Yes, it has been through a factory reset. It's not a huge problem that the battery is bad, I just want consistency and be able to trust the percentage.

 

[Gav2k]

You battery has started to fail. Keep an eye on it as chances are it'll expand next.

 

[roanmy]

So... Get the battery replaced? The reason why I'm asking is that getting it replaced really isn't expensive, but I don't want to unless it'll actually help.

 

[jaypr]

Sounds to me like the battery has been replaced, but with a non genuine Apple battery.

I did something similar with my sister-in-laws iPhone 4s battery a few weeks ago. After I'd replaced the battery the percentage is all over the place. The battery lasts much longer now. But it'll stay on 98% for 18 hours without moving or it'll die at 15% without warning.

She's happy as it lasts days now instead of hours, but I have know idea why it is like this after the battery was replaced.

 

[roanmy]

Hmm, there's a repair shop here offering a new OEM battery relatively cheap. Think it'll solve my issue?

 

[Broadus]

Hmm, there's a repair shop here offering a new OEM battery relatively cheap. Think it'll solve my issue?

I suspect it would. Like I said, I've done it twice and mine's still going strong.

 

[nordique]

Yep sounds like battery needs replacing. Usually if you've restored everything and reset everything, once it turns off at a certain power level (like say 30% or 40%) on a regular basis, it needs to be replaced

Especially if its used, as depending on the age of the 4s, it can be closing in on 4 years old now which is more than enough time to drain a battery (or 2 as stated above!)

Replacing a battery is easy to do by yourself, but if they're offering to do it for cheap (like 20 dollars) might as well do it via them. OEM only; don't use any larger or smaller capacity amounts.