Questions about smartphone batteries

Installed a battery app on LG G4 called Accubattery. It says battery is about 83% healthy. The device has been used moderately since May 2015 (purchased on its release date). Is this about right for battery decline over time?

I have a spare battery that has been sitting in a drawer for the past 2 years. Should I have been doing anything to keep it healthy over that time period? The one thing I have been careful about is keeping the house cool year round since heat is supposed to be bad for li-ion batteries.

For the newer smartphones without removable batteries, are there pro services to replace batteries after a couple of years? If so, how much does it cost? Or do people just dump the devices when batteries are not user-removable, making the devices basically disposable?

See if there is a Batteries + Bulbs in your city. The one near me quoted $60 to install a new battery. I was told that they may also offer a 1 or 2 year, or in some cases, a lifetime warranty on the battery. The length of warranty will vary dependent on what phone you have and what battery it requires.

The G4 has a removable battery so it would only require just ordering a new one and preferably ONLY an OEM battery from LG or a seller that guarantees it's an actual LG OEM battery and not some cheap Chinese manufactured "it works in a G4" type thing that so many on eBay and other online services have. As far as the battery life and the wear on it so far that's not too bad I suppose but perhaps just a bit more than I might expect in just shy of a year of use but that all depends on how often you charge it as well as how you use it (full brightness on the display most of the time, or CPU/GPU intensive actions like playing a lot of games, etc - music and video playback nowadays are actions that just sip battery power but games still kill batteries faster than anything else and by "kill batteries" I mean on a per charge basis.

Since Li-Ion batteries have a limited lifespan typically measured in years anything that really drains them with regularity and warms them up - which is what happens when you play games due to their high-power drain requirements - will shorten that overall lifespan. Lifespan != battery life, for the record because it's a confusing set of terms to say "battery life" and most folks think that means the per-charge run time when I'm speaking of the actual lifespan of the battery itself. The battery you have in that G4 right now has a date code stamped on it (or it should if it's an OEM battery which it should be since it's probably the one that came with it in the box).

If you have a spare battery - the same battery the G4 uses and the G4 was released in early 2014 - if it's an OEM LG battery it too should have a date code stamped on it. If it hasn't been used in the entire time you've had it aka it's literally been sitting in a drawer till now I'd suggest using that from now on at least for a few months, then start doing a weekly swap of the batteries. Like I said, it's removable so it takes like 30 seconds at most to remove the back cover, drop the battery out, put the other battery in, put the cover on and you're good to go. Swapping them would give you better run times overall especially if the "spare" battery hasn't been used since it was made.

I'm curious to know why you'd have a spare G4 battery that you haven't used and even more so why you'd have that battery for a year prior to owning a G4 unless you had a G4 prior to the one you bought in May 2015. I've owned 3 LG G4 devices and right now I honestly still wish I had one but the boot loop issues make them questionable purchases nowadays, but if I find one for a great price I'm still going to get another one for sure, my fave smartphone ever.

As for newer or other devices without removable batteries the manufacturers act like they should provide at least 90% of the original battery capacity for 18-24 months depending on usage. Of course they won't ever provide a warranty for that and batteries don't always have coverage even under the typical 1-year parts and labor warranty period most manufacturers give their products of this nature so that's somewhat stupid I suppose. There's no absolute way say whether a battery will fail or not because they can't know how you use your device so there's no way to guarantee a given level of lifespan over a given period of time. Battery replacement pricing isn't something that's "locked in" either and most shops tend to charge $50-100 (at least here in the US) to do a swap but it depends on the model - iPhones and Galaxy devices being so popular means more people replacing their batteries so the prices are usually lower, but for fringe devices like stuff from Motorola or other brands would cost more because they'd probably be special order due to the unpopularity.

But again the advice is start swapping the batteries you do have and you'll have use of that G4 for longer periods of time I'd say.

Tiberian: clearing up some misunderstandings from the post above. G4 was released in mid 2015, I got mine on release date. LG had a promo where they gave a spare battery and micro sd card with purchase. So the battery was at same time as G4 purchase.

Questions about non-removable batteries are because I am looking at newer models like the G6. So it would be nice to know the implications of having that vs removable on the G4.

I am going to collect some more stats using Accubattery for a few more days (it says estimates like battery health are more accurate with more data points). Then try switching the spare battery to compare results. Thank you all for responses to questions.

Ideally you would have wanted to charge the spare every month or so. Honestly, I don't see it being a huge issue if you started using it now as it is.

That being said, I wouldn't really worry about it much.