Different strokes. Set a Megawatt 400 to 14.8 with an adjustable 4-hour spring wound timer and the battery will charge to 100%. The difference between this and the old fashioned chargers is the voltage limit of 14.8
Older chargers open circuit are 17.0+ volts - battery boilers. Setting the Mega to 14.8 delays overcharging to the point where it's a no-brainer. Of course some people do not like the idea of having to add cables and a timer to a power supply. If I reach 90 years of age in 20 years maybe I won't want to do that. I did exactly that yesterday to a 36-amp Megawatt for my son'in-law. I would not pay $5 for today's off the shelf gahbage. The partially full concept is like a 20 gallon gas tank that holds 18 gallons and the next station is 19.6 gallons distant. You gotta be ------- me.