here is a brief explanation

lipos are more sensitive to over charge so you want as much voltage monitoring as you can. most lipo batteries have a second smaller plug (in addition to the main power wires) that has leads to every voltage level (cell) in the battery. this 2nd plug is called a balance plug and allows the charger or a seperate balancer to monitor the voltage of the individual cells and make sure they are all even and not over the maximum safe voltage of 4.2v per cell.

for a 2s pack you would have your negative (ground) pin, followed by your first positive pin that is connected to the positive end of the first cell. then you have the 3rd lead/pin that is at the end of the second cell. the balancer would read the voltage between ground and the first positive pin to check voltage on cell 1. then between the first positive pin and the second positive pin to measure cell 2. this is because the 1st positive pin is ground relative to the second cell.

for higher S batteries (3s, 4s, 5s, etc) there is simply another positive pin added to the balance plug for each additional cell.

some chargers will actually charge through the balance plug but this should only be for 1amp or less of charge current.

so i am guessing you need to take apart your battery and add this extra plug. lots of manufacturers offer them seperately and there are a few different standards. make sure to get one that works with your equipment.

im too lazy right now to find links to websites with more info, but if you need more help just ask.