The L16 shouldn't be too badly damaged by one over-discharge. It's a pretty robust battery
Assuming you're running a 12 volt system, the manufacturer's spec sheet for that battery
would suggest that you need to charge at 14.8 V, float charge at 13.2 V, and equalize at 15.5 V (assuming 25 Celsius ambient temperature).
I would suggest checking the water
level in all cells, charging
them properly (14.8 V, then 13.2 V, stop when the smart charger cuts off), then equalizing. A 10 amp all-purpose charger can't do this; you need a multi-stage one that's designed for high-current banks.