How does Apple decide whether the battery is elible for a warranty replacement? It is running hot and does not hold a charge.

Take it to the Genius and they will say yea or nay. My experience is they will say yea if they can at all.

Apple has been surprisingly good to me with battery replacements. Basically if it's within the computer's warranty period, and the battery says it's bad, they replace it for free. It will show a status of "Check Battery" in system profiler. If the batter is "consumed" (you have exceeded its recommended cycle count) it will probably have a status of "Replace Battery", and they may not replace it.

For a long time, and until only somewhat recently, batteries were expected to last 300 cycles. But the advent of non-replaceable batteries caused a shift in this policy, and now batteries are expected to last 1,000 cycles. So odds are good that by the time you have a battery problem, it's going to be out of warranty. (or it will have its problem under warranty and will be replaced for free)

In a few cases you get more than just the battery. Some macs had the battery glued to the underside of the top case, and so you get a whole new top case, complete with new keyboard too. iirc that was on a group of macbook airs.

If your battery is swelling, Apple may pay for further repairs, and has been known to cover repairs on machines that are out of warranty. I've seen some impressive "airbags deployed" in my time. Swelling batteries typically caused problems with the laptop rocking on the table, problems with clicking the trackpad button, and ultimately being difficult or impossible to remove. I recall having to mail in a couple of laptops for battery replacement because I couldn't get the old one out. Those came back with some parts replaced, as they must have had to break in to relieve the latch.

http://vftp.net/mac_disasters/batteries_swelling/

Thanks!

it still amazes me just how airtight they made those cells. I was NOT kidding when I labeled that one "inflate to 35psi". I seriously doubt I could TAPE anything that airtight.

Doesn't that mean if it overheats enough it could explode?!!! I've never heard of that happening...

Virtually any sealed system can explode if heated to a high enough temperature and the seals do not let go and allow the pressure to dissipate, and in fact there have been cases of lithium ion batteries exploding (early models of the Boeing 777 airliner being a prime example). But at the power levels in an iPhone or MacBook it is far more likely the system will be put permanently out of commission by battery swelling long before a temperature is reached that might cause an explosion. Battery swelling has occurred in Apple products, most notably some MacBook Pro models.

V1, you need a website, I love your pic collection.

https://www.youtube.com/watch?v=tatq8KcaGY0

and many many more. it's not so much an explosion as it is a highly energetic combustion... The electrical short generates lots of flammable gas and heat, with the expected results.