Charging 4 12-volt house batteries with portable charger

Now let's look at that "battery science" (B.S. for short) claim:

In order to accomplish such a thing, two things would have to be a given.

1) The charger would have to be charging at a less than C/6 rate:

100Ah battery; 100/6.6 = 15a; 50-80% = 30Ah / 15a = 2 hrs,

2) The charge cycle would have to be a 50-85%.

At 13.6v, the amps would drop drastically and only about 5Ah's would be replaced in one hour.