Rejuvenating an old flat battery...with urine???

[Lanciaman]

I have a battery that has been flat for a number of years - 5 or 6. I've been told it's possible to rejuvenate it by putting it on a trickle charge and being patient, leave on charge for possibly as much as 2 or 3 days. The advice was check the electrolyte level, and if low, add urine. Anyone heard of this before??
I have had a quick Google and read Epsom salts can be used, but urine is readily available here, so that would be easier!
Any advice welcome, Happy Easter everyone.

[Mocki]

If that battery has fallen below 9v no matter how you may get it to charge , it is FuBar
It will never be any good , nor reliable

Adding any for of acidic liquid will likely "pep" it up and invoke a little extra chemical faction, but like all other "magic" remedies it won’t actually work

[Lanciaman]

As I suspected, thank you for your reply. It's showing 4.6V before any charging attempts, so as you say, finito.