Hi Lucy, very good question- all I know is my charger just doesn't want to know when I plug the balance wire in to
the correct slot on my 1 to 6 S charger-the voltage is just too high 33 volts plus.
when I tried plugging both balance wires in sparks flew but luckily I was quick to pull it out-but you are right one connector
is a 4 S and one a 5 S.
I'm now thinking I made a mistake buying them as the chargers available are well over £100.