> Any "new" used phone is going to come with a battery of undetermined age and quality as well as its own set of potential problems and failures

Not necessarily, as I can't imagine most refurb/used sales worldwide come from individual sellers; most of them are probably sold by businesses, which sometimes provide a warranty and return policy on their used products. Right now, on the Amazon Renewed Store, the unlocked Galaxy S20 FE 5G 128GB is $187.50. Amazon states,

> The product is refurbished, fully functional, and in excellent condition. Backed by the 90-day Amazon Renewed Guarantee.

> - This pre-owned product has been professionally inspected, tested and cleaned by Amazon qualified vendors.

> - This product is in "Excellent condition". The screen and body show no signs of cosmetic damage visible from 12 inches away.

> - This product will have a battery that exceeds 80% capacity relative to new.

> ...

> - This product is eligible for a replacement or refund within 90-days of receipt if it does not work as expected.

from https://www.amazon.com/Samsung-Galaxy-128GB-Cloud-Mint/dp/B0...

So if 2.5 months into using that phone, you feel it doesn't function well, you can return it.

Even for sales from individuals, Swappa (an online user-to-user marketplace for used tech) requires you to list the battery health percentage on iPhones if it's below 80%. They also require that everything functions well and even is in good cosmetic condition. Their standard for "fair" is rather high.

Outside of pawn shops, I imagine most brick and mortar stores aren't selling phones in poor condition. In the US, the phone carriers, Best Buy, and even Apple themselves sell refurb phones, and they don't want to hurt their reputation by selling poor quality products. Apple in particular has high standards for their refurb phones:

> All refurbished iPhone models come with a new battery, new outer shell, are backed by a one-year warranty, have free delivery and returns, and also include:

> - Full functional testing, genuine Apple part replacements (if necessary), and a thorough cleaning

> - The original Operating System or a more recent version

> - All refurbished devices are repackaged in a brand new box with all accessories and cables

I guess anecdotally my iPhone 6S as of recently hasn't been performing well. Would a battery replacement help it? Maybe. But that's not certain (it could be that modern apps are so bloated that its 2015 hardware can't handle it despite most of those apps having essentially 0 new meaningful features in the past 8 years) and I'm surely not going to spend $100 on a nearly 8 year old phone to find out. I've replaced the battery myself before, but last time I broke the screen in the process (something that wouldn't have happened if the phone had a removable back), so I'm hesitant to do it again (I was being careful, and have done plenty of phone repairs at this point, but more than anything the ribbon cables break extremely easily.) But if I could just pop off the back and put a new battery in, I'd be willing to give it a try for $35. But instead I'll probably just deal with it for a little while and then get a different used or refurb phone with better battery health than my own device.

EDIT: another example of an affordable refurb phone: iPhone SE (2nd gen) is $147 in the US from the Amazon Renewed Store and has all the same benefits Amazon guarantees for the Galaxy S20 FE. So for $47 more than a battery replacement, you can essentially try out a "new" used phone for 80 days and determine whether you want to stick with it or return it.

https://www.amazon.com/Apple-iPhone-SE-64GB-Red/