There is a 1996 Sandia study with the title "A study of lead-acid battery efficiency near top-of-charge and the impact on PV system design" for charge and discharge lead-acid battery amp hour [Ah] efficiency at different states of charge (SoC) for a Trojan 30XHS low-antimony flood lead acid battery.
However these results are measured using a charge current of only 3.3 amps per 100Ah of rated battery capacity. Real world PV/solar charge current are much more varying and at least have high peaks. That is one of the reasons why AGM is chosen, the ability to charge with up to 40 amps per 100Ah of rated capacity. Manufacturers for solar OPzS (flooded lead acid batteries) do allow charge current of 35 amps per 100Ah of rated C10 capacity.
Watt hour efficiency
Due to the fact that charging voltage is higher then discharging voltage, the nett effective Wh power efficiency is always lower then the Ah efficiency. And that Wh-efficiency is the only (real world) efficiency statistic I am interested in.
The only numbers I could find are in this "Electrolyte mixing for VLA cells" document from Hoppecke at page 10, with 10 amps per 100Ah charge current and from 50 to 106% SoC resulting in a watt hour [Wh] efficiency of 71.6%.
Is there any study know for flooded lead acid charge/discharge watt hour efficiencies at higher then 0.033C charge currents?