Single cell charging circuitries are pretty much always the same: depending on the battery type there is a voltage cutoff, regardless of the capacity. So in theory the new battery would charge with the same current as the old battery, thus taking longer for a full charge, it should fully charge nonetheless though. Other considerations might be heating of the involved components when charging over three times as long.
Very sophisticated charging mechanisms might measure the time/current and calculate the capacity of the battery, but this is usually done in laptops, smartphones and other devices that go through lots of charging cycles.

Thanks for the info man, I installed the new battery, the headphone circuit charged it under 4 hours and it's been in constant use every since ( 9 hours of playtime so far). I didn't have to buy a replacement battery for $30. I added a clip lead so I can just switch around li-ion batteries without having to disassemble the headphone ever again. It won't win a designer award but it works.

Good stuff. The only way round you need to be more careful is putting a lower capacity in place of a higher capacity, when the charger could overheat it by charging too fast.

There is also maybe a problem with factory fresh new cells of larger capacity than design as apparently some need a particular charge rate and discharge to "intialise" them properly. So potentially you stick a brand new 2000mAh cell in your device that took 700mAh and only end up achieving 1500mAh with it or something. Should not happen with reclaimed cells though.

I got pouch cells going up like startled puffer fish round here. Even things I just bought cheap to steal the cells from for other stuff.

BitWrangler wrote on 2023-07-31, 18:20:

I got pouch cells going up like startled puffer fish round here. Even things I just bought cheap to steal the cells from for other stuff.

I never even considered using different batteries until I checked the original battery prices on these devices. C'mon, a 600 mAh battery for $30? That's a crime. I bought that headset for $45 new and they are still for sale $40 today! So battery prices made this otherwise good product disposable. Sad.

Yup, though they're a bit cheaper if you can find them on aliexpress or similar, but usually the shipping takes long enough I forget what I wanted it for, or time moved, project got stale, found a workaround etc.

I think I'm gonna move to putting external 16450 holders on stuff, or dangling on a dongle, dedicate a "universal" lithium charger I've got to just charging 16450s spare to keep swapping round... at least you're handling them often enough to catch timebombs.

BitWrangler wrote on 2023-07-31, 19:44:

Yup, though they're a bit cheaper if you can find them on aliexpress or similar, but usually the shipping takes long enough I forget what I wanted it for, or time moved, project got stale, found a workaround etc.

I think I'm gonna move to putting external 16450 holders on stuff, or dangling on a dongle, dedicate a "universal" lithium charger I've got to just charging 16450s spare to keep swapping round... at least you're handling them often enough to catch timebombs.

I don't trust anything from China, I bought a replacement battery for an Xperia X marketed as genuine a few years back and it was complete crap. Same with LCD assemblies, the quality varies too wildly for my taste.
The 16450 idea is good though, solves the headache of small capacity built-in batteries that start failing after 3 years.