Does reconditioning batteries really work?

YES!  They work pretty good too!

Sometimes

Once a battery has been left dead too long, it will never come back to full capacity.

Many new cars have gone to AGM batteries for that reason

AGM batteries will survive deep discharges from leaving your lights on and running them dead where as traditional lead acid starting batteries will be damaged by it

Where do you live?  There is no such thing as a reconditioned battery in the USA and there never has been.  Trying to recondition a battery is just stupid.

Buying a reconditioned battery means the only old part is the plastic case.    The recon shop cuts the top off the battery and GUTS IT.  Then puts in new lead plates and new acid and reseals the top back on the battery.  Everything is new except that it no longer is FROM THAT COMPANY.  So they paint over the old name so it is a No Name battery.  They put a 5 year guarantee on the battery and sell it for A LOT LESS.

I bought a 1000A recon battery for $35.  At a store I checked the price and at Wally's I could get a name brand battery that had 850A for over $240 for 5 yr guaranty.   I could buy the recon 7 times(if the battery only lasted 1 year and had no guaranty.  With the guaranty, that meant a dozen batteries for the one price of $35.  Installation is easy to do, any clown can do it if you got a wrench and a microscopic bit of smarts.

They have been recycling batteries since they invented them...so it is not a new science.  This is the lead acid batteries for cars, right? They had them at Costco for a time, otherwise the Battery doctor would have reconditioned batteries. 

. The mickey mouse home saver techniques do not work because of Chemistry. and lead falling out of the grid screen.  Once it disconnects from the grid then there is no power from that chunk of lead...as it must touch the rest of the lead to make a connection. 5 year batteries will go 7 years before dead.  10 year batteries go 10 A 10 year battery costs twice the cost of a 5 year battery so you don't win.  A Battery shop will give you a couple of bucks for your old battery, as they will take it apart and rebuild it.   So, if you get a couple bucks for the worn out battery you subtract that off the purchase price of a battery.  Wally's won't give you anything for your core...because they don't rebuild batteries. They don't recycle anything.

. Recon a battery yourself is not possible so not a DIY job.  Face it, when you need to jump start the car you need a new battery.(so $100) probably because you are not going to find a recon battery shop nearby today.  Even $100 for a new battery is not a bad price if it is going to last you 7 years.  Unless you are like those idiots in the movies.  They leave the headlights on when they shut off the car.   Yeah that won't take long to kill the battery.  Now you need a jump. Which is the pits when you are in the middle of nowhere.

Depends on how it's done - - mostly it's just a scam

There have been pills and potions to reinvigorate old storage battery  back to 1920 . . . and in the 1980s the thing was "pyramid power":  put your old battery (or razor blades or stale bread, whathaveyou) under a pyramid and it would be renewed over night.  Sure it will.

Why bother?  I'm not happy with the price of batteries to day . . . . I just put one in my car and it was $165.  But the old one lasted 8 years . . . . for 6 cents a day, I'm not gonna risk being stuck in the middle of nowhere.

Most of the pills and potions purport to clean deposits off battery plates . . . . may give you a few days of good starts . . . . but all the gunk is accumulating in the bottom and the whole thing will shortout and go totally dead.  But a new one.

A new battery will last 3-5 years at a cost of maybe £75. That’s around £20 a year. A reconditioned battery might cost half, so is it worth £10 a year to be stranded somewhere?

No and it's not only dumb to try it it's also dangerous messing with the acid.

yes, sometimes..........

How., when, where. What kind of batteries? My Craftsman drill batteries failed to be renewed by the bullshit posted on the internet. My answer is no, it does not work.