Nothing higher than 14.4 really your best off closer to 14v. This is why lto is so advantageous.
Lifepo4 really doesn't fully kick in till 13.6v in 4s banks
Lto kicks in at 14.4v in a 6s bank
So while lifepo4 will have an overall higher state of charge you will still have to drop to 13.6v before the battery really starts to help.
Alot of guys are running 6s lto and only charging to 14.6v and optimally 15-15.5v is all you need to get maximum value from lto banks.
All battery's have voltage drop but the closer your charge voltage is to the rest voltage the less the change in voltage is thus a less noticeable drop. This comes at the expense of state of charge.