There are a few different connectors popular in radio controlled models these days. There is also some confusion about their names, and how to find some for your projects.
Many of the micro and mini multi-copter models use the same type of two wire connectors on their 1S battery packs. These connectors have a pin pitch (spacing) of 2mm. Different names are used for these connectors, including: Micro Losi, JST-DS, Micro-T, and Molex. They are, in fact, Molex connectors, or compatible copies. Molex describes them as 2-way 1-row MicroBlade™ Wire-to-wire Receptacle Housings. The part numbers are 51005-0200 for the female housing, which is the piece without the visible pins, and 51006-0200 for the male housing with the exposed pins. Many users and sellers get this terminology backward, since the female connector slides inside of the male connector1.
They can be hard to unplug, especially when attached to flimsy or delicate equipment. There are little nubs molded into the plastic of the female connector. These nubs snap into a recession in the male connector. The nub, and the recession where it seats, are circled in the close-up photo.
You can remove some of the material from these nubs, so that the connectors are not as difficult to separate. There will still be enough friction in the connection to keep it from falling loose in normal use. A small file, or a sharp knife can be used to remove the excess plastic. I have had the best results using a very sharp knife, such as an X-ACTO® blade. You can now unplug the connectors without feeling that you are going to pull the pins out of the housing.
Searching for a source of these connectors can be hard because of all the different names that they go by. And unless you just love crimping tiny connectors to tiny wires, you will not want to buy the empty pin housings and separate crimp terminals. The best deal that I have seen on these connectors, complete with wire leads, is from Banggood.
Not all suppliers and manufacturers use the same polarity. All of the batteries and connectors that I have seen so far have the polarity as shown in the photo above. You should still carefully check the polarity of your existing batteries and connectors before connecting any modified or rewired batteries.
1 The radio controlled hobby industry commonly classifies male and female connectors based on the “sex” of the housing, and not the pins. So a shrouded housing, containing pins will be called the “female”, while the plug housing with the sockets will be called the “male”. This is opposite of the terminology common in the rest of the electronics industry. Pay close attention for this difference when ordering or specifying connectors and wire harnesses. The Hansen Hobbies website has a handy reference on RC modelling connectors.