Clearly I’m behind the curve here

Best I can tell, the situation is thus:

In general, you can find someone who opens up phones and replaces the battery for you. The batteries are of two sorts – real ones which will work and last a couple of years before showing signs of not holding charge that well, and things which look like batteries, cost the shop a penny, and may or may not work for some amount of time.

It helps therefore to know what sort of shop it is. There’s a chain in the USA called (horribly) U Break I Fix; they probably use only real working batteries. Fred’s OK Phone Repair Shoppe which wasn’t there six months ago may not be up to the same standards.

In the USA, a typical replace the battery operation (for an iPhone) seems to be about $70.

You may find that buying a replacement is the best thing to do.

Or you can go the route we just did – she didn’t check the pockets, and so my phone got washed for 30 minutes. I wondered why the washing machine was making washy noises interrupted by the occasional BONK.. For some reason it doesn’t work any more, so I bought an Apple refurb of nearly the same model. New iPhones are about 50% more expensive in France than the retail price in the USA, so the idea was to buy an old machine at a low price, and trade it in in the next year or so in the USA, losing a lot less money than buying an iPhone 12 here.

In Bernay there’s a phone repair shop down the road from the SFR shop, and they said good things about it. Perhaps the Vodafolk could point you at a reputable repeairer and then you could ask said RR about replacement batteries…

Most phones these days are built front to back, meaning the battery is one of the last things to go in before the back is glued on. You can get a replacement battery online for under £20 and it only takes 10 mins with a hairdryer and guitar pick to do the job. Depending on the phone (glass or plastic back) you may need to also order a new rear cover as the glass ones tend to break when prying them off. If that’s the case make sure you get one with the adhesive pre-installed, then it’s a simple peel and press job. Also power on the phone before sticking the back on just to make sure the battery connection is good! Youtube is your friend – there will be a tutorial on there showing you step by step how to do it; it’s really not hard.

I’m of the ‘time to get another phone’ persuasion. For the reason BiTiN explained, and especially because I use iPhones. I pay 100 quid ish for a pristine refurb of whatever model fits the bill and they last a couple of years. Always the battery is what dies.

I’ve had a 6s for nearly two years and guess what? Battery charge is now fairly useless. I’m hoping to hold out until an iPhone 7 comes in at under 100 notes.

It’s all part of planned obsolescence to keep the phone industry and the networks churning customers onto ever more lucrative subscriptions

Try iFixit

They sell battery replacement kits

Did my motog4, now running for five years, one of them on the replacement battery that I put in using their kit
They even have videos telling you how to do it step by step

Replacement costs around 20-30%of the cost of a new phone, plus you get a handy toolkit for small electronic devices!

They do kits for tablets etc too

I buy a shiny new (android) phone every 5 years or so, laptops rather less frequently. I’ve never had any battery problems. What am I doing wrong?

Others are commenting about whether or not a battery can physically be replaced, but I suspect that sourcing a new battery is the problem here. If its an operator branded phone it may have had a limited production run and there may just not be any spare parts available for repairs. I’d check ebay and the like to see if its actually a thing you can buy before doing too much further research.

I’d also consider a new phone. The sad fact is that most of this kind don’t get any security (or any other) updates which a new phone will have. Add the risk of buying a dodgy battery and it might just be best to get a replacement newer cheap phone instead.