House Battery Wiring
First, in both diagrams the voltage (if measured to ground) does not make sense. You can't have two different voltages on the left of each diagram from the same terminal (12.x and 4.x and 12 and no reading), look at your red lines.
Next, all positives could go to the same place and the same with the grounds. However, since only so many terminals will fit on a post, the are often tied to different post in the series/parallel situation.
Lastly, 2-6volt batteries have to be in series to get the required 12 volts. 4-6volt batteries would just be two sets of series batteries and the sets in parallel.
As a side note, there are many series/parallel drawing on the Internet for reference.