I have an old Apple SE phone. Since an software update a while back my battery loses charge randomly. Sometimes it goes from 100 to 0% other times 70 to 0 over a 2 hour ride with Strava on but data off no pics, phone calls, etc. My question is it worth paying Apple to change the battery or save money by going to a local shop but risk it not upgrading in the future?
No. Bin it & get an XR.
I'm not sure what the price difference is, but aftermarket batteries can be had pretty cheaply (tenner off eBay IIRC) and work OK. You can DIY it fairly easily too. Just don't expect them to last as long (in terms of overall lifespan of the battery, in months/years) as a genuine replacement.
I don't think there's any issue re: updates. What probably happened in your case was that Apple removed the 'make old phone go slow to preserve dodgy battery's life and stop instant switch offs' protection because people saw it as evidence of them making older devices obsolete. Either way, a new battery should sort it out.
Assuming your OS is up to date you can ask it how healthy the battery is and what’s using the power. I’d do that before assuming a new battery will fix your problem; I’ve had apps that randomly start eating power, those using location services seem particularly prone to this.
Our old 6S phones are running new batteries from the local phone repair place. I'm happy to pay someone to swap them as whilst the battery change isn't impossible it's not trivial either.
I’ve got the same handset. Gave up with Strava...well actually gave up using it as a cycle computer because it is really affected by the temperature. Got the same problem when I’m using my indoor trainer as it’s directly in front of the fan. Otherwise it’s fine. It’ll last a day of reasonably heavy use. I’m too tight to pay someone to change the battery. Will probably wait till there’s a offer on an newish handset
I replaced the battery in my old SE with an aftermarket one well over a year ago and it is still going strong.
there are plenty of good videos online so you can check out how to do it and decide if you want to do it yourself or send it off.
replaced the battery in my old SE with an aftermarket one well over a year ago and it is still going strong.
I did the same and still all good.
One thing that isn't is almost every time I take a photo it stops the strava recording.....odd
It's £49 to get Apple to do it. I've had mixed results with after-market ones. When my son's hand-me-down 6S was suffering with really poor battery life, it seemed a no-brainer to drop it into the Apple store. Picked it up 1h later. All good.
Not so easy with everything being shut just now but hopefully things are opening soon.
I had the same issue. I took it to a phone shop and they did me a new battery for £25 and it took 10 mins. I can now do a ride without having to take out a charger as well as my phone.
We gave up on old SE model that was 3 and a bit years with the odd battery behaviour. Cold weather seemed to destroy the battery in minutes. I looked into battery costs and....we took out a new contract on box open 2020 SE instead.
Happier mrs_oab and sold the old phone for £50 iirc.
This thread turned out different to what I expected:

*B'DOING!!!*
New battery fixed my SE. It would go from 100% to zero in cold temps even when switched off. Its fine now.
Which magazine have released an article in the last day or two about phone updates and suggesting that the original SE has less than a year of support left. So it might be worth budgeting for an upgrade instead.
Just to be contrary.
I have an old iphone SE, battery died, twice, gave up on it and bought a Galaxy S10 5g, now* very happy. Don't worry about it being aquaphobic either which was always a major gripe with the SE.
*within reason obviously, coz it's all just a clustercluck with life in general right now
What does it mean when Apple stop the support for a phone?
I’ve got the old SE because I like how small it is. Will I not be able to use it a year from now?
It will still work, but won't be updated to fix security vulnerabilities.
Mine was doing the same. Battery health was 84% but after an iOS update at start of the year it was awful. I just called it a day and got a new SE which is great. It is only slightly bigger and almost as comfortable to use one handed.
I only ever have to charge it every other day which is not something I have ever been able to do with old SE. The old SE also won't get the iOS 15 update later this year so time to go anyway.
New battery fixed my SE. It would go from 100% to zero in cold temps
Mine regularly drops straight to 1% when i go out in the morning and it's below freezing. It keeps working without any issues for hours at 1%. It all followed on from a software update. I'll put a new battery in it at some point but for now it works for what i use it for and is yet to actually turn off.
Apple every time. I've never been happy with non-OEM batteries in any device I've had them fitted to and Apples charges are pretty reasonable.
I have a similar situation with a 6s. Checked the battery health in settings and it said it was 88%. Had a long appointment at Apple store who did lots of tests. They concluded that it was a software issue and not a hardware one. They said the only solution was a clean install I.e wipe it and start again. They said not to use a back up either to re-install. Haven’t got round to it yet as it’s a real hassle and I haven’t got the time at the moment. It may be worth trying that first if your battery health is still above 80%.