"Going to the load and the charger connected to + on one battery and – on the other battery"

By using three parallel batteries in the bank, and connecting load to positive on battery #1 and negative on battery #3 you draw current evenly from all batteries as a single bank. If you connected load to "+" and "-" of the same battery, the others in the same bank would be slightly lower voltage while charging and slightly higher when discharging -- there would be a slight difference in voltage potential.