I am using JST SM connectors for connecting two sets of wire. There are two slots in 2-pin connector. I wish to know, what is general convention for assigning the polarity to these slots? Is it slot 1-ground & slot 2-Vcc or slot 1-Vcc & slot 2-ground? Also how should I assign these slots for control pins(like clk/sw/sck)? Is there any uniform convention? And what is general assignment of slots in case of 3-pin connector? I have attached an image of the connector with visible slot numbers. Any Help is appreciated.

Image attached - JST SM2.5 connector(Male & Female with slot numbers)

  • \$\begingroup\$ As long as you don't follow a standard, I don't think there is a convention. \$\endgroup\$
    – Arsenal
    Feb 14, 2018 at 8:41
  • \$\begingroup\$ I like to put ground at pin 1, but that’s just a personal preference. \$\endgroup\$
    – DoxyLover
    Feb 14, 2018 at 9:01

2 Answers 2


Surely the standard has already been set by the battery manufacturers? I have many toy 4.8v NiCd battery packs wired with pin 1 Vcc and Pin 2 ground. Using these as stand-alone plugs and sockets there is no problem, but wishing to use one of these pre-wired battery packs, it becomes important.

  • \$\begingroup\$ If these connectors are already often used for battery packs, the OP may want to consider using something else to avoid confusion. \$\endgroup\$
    – user39382
    Feb 24, 2018 at 1:27
  • \$\begingroup\$ Thank you for your comment duskwuff... however, one can purchase these connectors already wired (as in the top example) both ways. If the battery manufacturers have chosen a polarity, surely the standard has been set by them? I like this connector for low current applications as they lock shut. I could change the female plug on the battery, but that would render the supplied chargers incorrect. \$\endgroup\$
    – David
    Feb 24, 2018 at 1:57
  • \$\begingroup\$ I'm not sure I follow. The OP didn't mention a battery anywhere -- they mentioned that the connector might be used for power, but that could just as easily be 12V as it could 3.7V or 4.8V… \$\endgroup\$
    – user39382
    Feb 24, 2018 at 2:02

I spent some time looking too (in my case for a JST XH 2-pin battery connector polarity standard). Did not find any standards/conventions.

  • Batteries from different manufacturers (in my case 1-cell LiPo batteries) use different polarity.
  • Connectors sold separately (with attached wires in the male connector) also use different polarity depending on the manufacturer.

If you are making a PCB, try to indicate in the silkscreen of your board the connector polarity (i.e.: where "+" and "-" go) to make it clear for anybody (and for you when you forget in in the future).


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.