This info wasn't published...time spent charging =+ total amp hour capacity. I know of no lead acid battery that has recovered successfully from a 50% cell voltage that had spent time utterly and totally depleted. 0.00 volts, then a rebound to 50% voltage after extensive charging attempts.
With something like a Megawatt, current limiting through a light bulb (amperage throttle) is the only safeguard that would prevent runaway. A 25 watt bulb would limit current to two amperes and change.
Hasn't had a heartbeat in a half hour would be an appropriate analogy as to why mouth-to-mouth would be futile.
Sometimes it's best to yell "Uncle" and settle for a low battery cutout.