¿¿Huh??

what is the need of charging the new batteries for 250% of its capacity?
I don't know where you heard this nonsense.
Go to the battery manufacturers website for their recomendations.
Del

What on earth are you talking about? Charge a battery to 250% and you've ruined it.

I'm not letting you anywhere near my car!

I've seem manufacturers recommendation that you leave a NEW battery on a (smart) charger for 2-3 times longer than the typical recharge time. This helps to condition and fully "top off" new batteries. You are not actually pushing 200%-300% of capacity into these batteries. That amount of overcharge will permanently damage most batteries I'm familiar with.

For new battery manfacturs suggest to keep charging for long tine i.e., for 2 to 3 times of its normsl charging period because after manfacturing of battery it may kept aside without charging for long durration may be weeks or months, this leads to drop in battery voltage, electrolyte normality

generally for 12V battery or 6 cell battery flot voltage is 13.5V boost voltage is 13.8-14V and max discharge is 10.5V