How do I know negative or positive in a battery power plug?

[tomi1]

Hello guys, don't really know if this is the right place to ask for this, but anyway.. I have this plug which is the connector to charge an electric scooter battery

 

And I need to solder it to the cables that come from the battery (Red and Black) 

 

But I don't know which side of the little connector is positive and which is negative, so where do I solder each cable?

 

 

[Denniz]

If you have a multimeter you can test and check, but i would assume that the plug to the right is the positive (but i can be wrong).

[Needfuldoer]

It can be wired up either way. Make it match whatever's going to plug into it.

 

Center positive is the standard for pretty much everything except Sony, who uses center negative for some reason.

 

The pin on the right in your picture looks like it connects to the center pin, but you should tone it out with a multimeter if you're not sure. Check which of the pins has continuity with the center pin, and which connects to the outside.

[minibois]

Look at the charger that came with the scooter, as it can be either center positive or center negative (the latter former being more common). Then you just need to use a multimeter in continuity to test which of these plug(s) is center vs. outside.

 

For a little context, barrel jack connectors have an inside (center) and outside. A charger can either have the center as the negative or the center as the positive. This is indicated on the charger with one of these graphics: https://en.wikipedia.org/wiki/Polarity_symbols

This shows whether negative (black) is the center or if positive (red) is. You use a multimeter to test what part on the back corresponds with what part of the barrel jack.

[tomi1]

14 minutes ago, minibois said:

Look at the charger that came with the scooter, as it can be either center positive or center negative (the latter being more common). Then you just need to use a multimeter in continuity to test which of these plug(s) is center vs. outside.

 

For a little context, barrel jack connectors have an inside (center) and outside. A charger can either have the center as the negative or the center as the positive. This is indicated on the charger with one of these graphics: https://en.wikipedia.org/wiki/Polarity_symbols

This shows whether negative (black) is the center or if positive (red) is. You use a multimeter to test what part on the back corresponds with what part of the barrel jack.

Just checked the charger and indeed it has the Center Positive symbol.

 

So now, could you please explain how exactly do I test it with the multimeter?

 

Just to see if I understand correctly, if the right pin (on the pic) is the one that connects to the center, then that would be where I solder the red cable, and the black cable on the left?

 

Thanks a lot for the help guys, appreciate it

[Needfuldoer]

Use your multimeter to check which pins on the back connect to which pins in the face of the connector.

 

Pin 1 is positive, pin 2 is negative, pin 3 has nothing connected.

[RollyShed]

The centre pin is positive and the right hand tag in the picture.

Some sockets have a switch in them so if the device has an internal battery, it is switched off when a plug is inserted. In this case red to the centre pin (right hand tag) and the other two can be connected together, to negative, so which ever is needed is connected and it won't matter which.

 

As for Sony, and everyone else, with the centre pin negative, back in the days of germanium transistors and positive earthed radios and taperecorders. That was in the 1950-60s.

 

One other thing is the centre pin diameter. It used to be a thin one for 12 volts and thicker for 6 volts. This meant a 12 volt supply wouldn't plug into a 6 volt device. I've just come across a Rockwell power drill where the centre pin is thick, so thick nothing plugs in. So much for standards.

[Heats with Nvidia]

12 hours ago, RollyShed said:

The centre pin is positive and the right hand tag in the picture.

Some sockets have a switch in them so if the device has an internal battery, it is switched off when a plug is inserted. In this case red to the centre pin (right hand tag) and the other two can be connected together, to negative, so which ever is needed is connected and it won't matter which.

 

As for Sony, and everyone else, with the centre pin negative, back in the days of germanium transistors and positive earthed radios and taperecorders. That was in the 1950-60s.

 

One other thing is the centre pin diameter. It used to be a thin one for 12 volts and thicker for 6 volts. This meant a 12 volt supply wouldn't plug into a 6 volt device. I've just come across a Rockwell power drill where the centre pin is thick, so thick nothing plugs in. So much for standards.

In the majority of cases, the center pin is positive, but especially audio gear like guitar effects, are center negative. The problem is, there is no rea standard. Sometimes there just is one thats center negative. And by the way, the diameters of the outer shell and the diameter of the pin can vary a lot, or even worse, just a little, so it seems to fit, but not very well and you get contact problems.