Oh, yes, I had some funny experiences like this as well. Wanted to have the battery of my 17" MacBook (5.5 years old) replaced, as it started to inflate. (I have to admit, the battery had performed much better and longer than I had expected!) Made an appointment with the AppleStore; was told, that there are no replacement batteries for any MacBooks older than 5 years. As Apple doesn't officially recommend third-party batteries, this means in consequence, that you would be obliged to throw away the machine.
I told one of my customers, who has a lot of MacBooks in his company, about this. So he started to bring all MacBooks older than 4.5 years to Apple to get the batteries replaced. And every single time Apple made some suspicous battery-quality-tests and declared that the batteries were still good and didn't need to get replaced. (The batteries generally had a runtime of less than 30 minutes after 4.5 years).
"No, battery needs no replacement.", the Genius would reply.
"I do not ask for a free replacement, you know, I am aware I have to pay 140,- Euro for it. The battery runs only for 20 minutes, I do not think it is good."
"Yeah, maybe you have to calibrate it. But the test says, the battery is good."
"So, in 6 months I will get no new battery, as the model is legacy?"
"Ah, yes, this is true."
"So, would you please replace the battery, for 140,- Euro, please, please?"
"OK".
This dialog repeated for every single MacBook.
I switched to ThinkPad/Linux shortly after. Battery-wise doesn't seem to be much of a difference ;-)
I had the battery swelling in my 2007 Macbook Pro in 2013, and they happily replaced the battery for me. So in 2013 I had a 2007 Macbook Pro with a brand new battery =)
Also, at the time it had some ridiculously low cycle count due to a bug in the batteries firmware.
Guess I'm lucky. I found a replacement battery on ebay that's been fine. Looked exactly like the genuine Apple batter (aluminum jacket). I'm posting on it right now.
Yeah, a lot of people say that, but they also say if something goes wrong they'll sue. At least in the U.S. Sue happy here. Everyone wants that payout.
Compared to competitors, Lenovo batteries must be made of gold. I bought a third-party battery for ~$20. As I remember it, Lenovo wanted $75+ (their website indicates $180[1], but I'm not sure if this is the same model battery anymore.) The third-party here was Sony (or, so the battery claimed, at least, though having read enough articles like this I'm not entirely sure anymore). At any rate, the battery worked fine.
This, thankfully, was back in the day when the OEM crapware only loudly complained about me using a "non-genuine battery". Thankfully, the crapware runs only in Windows, and for the most part, I used Linux.
Haven't we seen enough hoverboards go up in flame to know even first-party stuff can sometimes be suspect? (and they're not the only example through the times of flaming batteries.)
Two simple 2300 mA Ni-MH cells from a decent Chinese brand like Pisen already cost $7.50. And you're putting an 8-cell battery on an expensive notebook, then use it on your lap?
So, you buy the cheap battery, the genuine cells, then you disassemble the cheap battery, reassemble it using the superior cells and then you also hack the firmware of either the battery or your laptop so it can still be charged.
Even just looking at the parts cost, are you sure you would still save money compared to going with the original battery? And of course you have to add your own time to this (if you actually like doing this, then it'll be cheap I guess) and the value of the warranty that you certainly will have voided at that point.
I totally understand that this might be a fun project to do and it will certainly be a nice achievement when you're through, but can this really be rationalised with cost of the original part?
You're making the significant assumption that the original part is either still available, or was ever available for individual sale (often, batteries that aren't considered user-replaceable are never sold directly.)
Apple systems are generally better off in this regard as vendors like iFixit can make official batteries available for older systems, but for other vendors, no such luck. For example: I can't find any source for an official Lenovo battery for my first-gen X1 Carbon. It's also long since out of warranty.
There is still the time consideration, but assuming you have time available to do the work, why not?
