If you want to buy a new phone in 2016, then apart from the price and the size of the screen, a phone's battery — how long it lasts, how big it is, and whether you can swap it out — is probably going to be one of your chief concerns. Some phones have removable batteries, and some don't. Here's the difference, why it matters, and whether it's worth putting a replaceable battery at the top of your wishlist.
The Upside: Easy Replacement, Quick Restarts, And Handy Backup Batteries
When you buy a phone with a removable battery, it'll either be accessible through a removable rear cover, or through some other ingenious mechanism like the LG G5's removable lower bezel, which can be swapped out for different modules. That battery will almost certainly be unique to whichever phone model it lives in — so you can't use a Samsung Galaxy S4 battery in a Samsung Galaxy S5, and so on.
I've been using a spare second battery for my LG G5 for a couple of weeks, and having the battery itself handy means that I've changed the way that I use my phone. I don't feel the obligation to plug it in when I get into my car to commute, when I get into the office, and throughout my workday or weekend — because I have another fully charged battery handy that I can just swap to if I need to.
Along the same lines, the G5's spare battery comes in its own charging case, using the same USB Type-C connector, which means you can charge it on your phone's charger whenever you've got the phone itself fully charged and operational. That charging case also lets you use the battery as a USB power bank to charge any other device — including your phone, though I'm not sure why you'd want to.
And finally, one small extra advantage of having a removable battery is that, if and when you need to, it's really easy to power down your phone immediately. If your phone starts playing music at full blast and you can't figure out why because there are no apps running — and it's happened to me more than a few times before, both on the G5 and on other phones as well — you can just pop the battery out and back in to quickly and easily restart the phone completely.
The Downside: Smaller Batteries Overall, No Water Resistance, A Thicker Chassis
Of course, having an easily removable battery inside a phone does come with its own set of downsides. The biggest one for most users — especially since, during everyday use, you're unlikely to actually have to remove and replace the battery in the first place — is that having a removable battery means that the battery itself has to be smaller. The LG G5's 2800mAh battery is relatively small for a 5.5-inch, 7.7mm-thick phone, when you consider the Samsung Galaxy S7 edge's 3600mAh cell is almost 30 per cent larger overall.
Removable batteries — in most cases — also remove the potential for waterproofing whichever phone they're used in. With exceptions like the Samsung Galaxy S5 proving the rule, almost all phones out there with removable batteries are not as precisely built as their sealed competitors, and that means they're more likely to die from water ingress during heavy rain or an accidental drop into a puddle or toilet bowl or pint of beer. Whether waterproofing is an important feature is up to your intended use, but it's worth considering which is more important.
Phones with integrated batteries also have generally slimmer bodies, because they're able to seal everything together with adhesive and maximise every millilitre of internal capacity — including with curved and stepped battery technology. As a general rule, removable batteries are much simpler and more traditionally designed, and that means they don't have the same no-holds-barred approach to battery capacity, trading it off for modularity. A removable battery, then, means your phone will be a little bit thicker — not hugely important when even thicker phones are still extremely thin these days, but if you're chasing the thinnest phone possible then you're going to struggle to find a removable battery inside.
As a general rule, we like a removable battery in a phone when we're travelling a lot. It's much easier to swap to a fully-charged backup battery than it is to wait for even the fastest-charging handset to fill itself back up, and having that second battery be its own USB power bank is incredibly convenient for any other gadget you're carrying. For day-to-day use, it's more often than not that we're travelling between chargers in the first place, so a non-removable battery's advantages — a slimmer design and waterproofing — are more useful in the long run.