A fortnight ago, in subzero temperatures, I took a short walk, during which my phone's battery (at about 75%) died abruptly in my pocket. It behaved fine after it warmed back up, and hasn't been out again in temperatures anywhere near that cold since, but today (Sunday), my 18 month old Nokia 6 started to act funny. It charged all night, but was at 93% charge when I got up, and the battery won't charge quickly (not that it charged fast on a good day anyway); the best estimate the machine can give me is 24+ hours to reach 100% charge from 44%. I've tried multiple USB cords, multiple wall plugs, multiple outlets (including the PC and an external battery) and even outlets in another building, and they all give me the same dismal result. I fashioned some tiny plastic into a makeshift dust remover and very carefully tried to clear out any dust there might have built up in the charge port, but nothing much came out, and yes I was careful to avoid hitting that little connector bit in there.
Is the battery on the way out? It's a non-removable battery so I'm going to take it to a phone repair shop tomorrow, hopefully it'll be a quick fix, but I was just wondering if the community thinks it might be some other problem, like with the charge port? It feels fairly firm and secure, and cables don't have a habit of falling out.
You could try recalibrating the li ion batteries built-in quality of life circuit by running it all the way down to 1% and charging back up as far as it will go (you may literally need to leave it plugged in for days) and doing a few discharge/recharge cycles like that. Sometimes the batteries can lose track of where the 1% and 100% actually is in the remaining energy in the cells (1% is actually more like 5-10% because if a li ion battery completely loses its charge it is strawberry floated, and it's damaged by overcharging as well). So the number you see doesn't necessarily reflect the actual status of the battery but just what its circuit is reporting it to be.
The battery should be ok even if in the cold, it's nickel cadmium batteries that get ruined by the cold.. If this does not improve say it never charges to 100 or drops out at 15-45% then yes it is reaching end of life.
Either way it is not going to last very long so you may as well get it replaced at some point. 18mo is typical time period for degredation to occur for a cheap battery and they all are cheap. The truth is batteries have never really been designed for constant use, discharge and recharge so they just fail after a couple of hundred cycles like this.
It is also better to let your battery discharge to a relatively low amount and charge it back up fully again, at least from time to time, although it's just a calibration issue that is why it starts to go out of whack. There is nothing wrong with "topping up" your battery but it shouldn't be used plugged in for long periods.
It's meant to be more like 2000 but that's bullshit, in actual usage with overheating, cold, thrashing the battery at low %, using while plugged in etc (i..e normal people) it's more like 500-1000 yeah which is pretty awful.
Batteries never and probablynever willl keep up with market demands as more and more power hungry stuff is put into phones.