On the output terminals of the battery pack, I’ve used 6 mm square wire or the equivalent of around 9 or 10 American Wire Gauge. I know that this is probably an overkill but I thought to better be safe than sorry.
I’ve soldered these wires to a XT60 connector, making sure to keep note on the polarity and I’ve added some shrink tubing on the wires to be slid on to the contacts to prevent any shorts.
In order to properly charge the pack and be able to monitor each cell voltage, we need to add a balance connector. This is an JST-XH 4 pin connector. One wire is connected to the negative side of the battery pack, while the other three are connected to the positive side of each of the three individual cells. This way, the charger can monitor the voltage of each cell and provide balanced charging of the pack.
Before connecting the balance connector, make sure that you identify the proper polarity as marked on the charger balance connectors.
While soldering make sure to trim the excess wires from the connector to provide neat connection.
Once all of the connections are made, use a multimeter to verify that the expected voltage on each of the pins is correct and that all of the wiring is correct. After that connect the balance connector to the charger and connect the main leads to the battery terminals in the XT60 connector.
The pack will need to be charged with a proper LiPo charger. This way you will not overcharge the individual cells of the pack and avoid damaging them. The charger I have is the iMax B6AC and it works perfectly.