My arduino uno doesn't power when I use a battery, I connected the positive with the vin and negative with gnd. When i used a disposable 9v battery, nothing happened. Then I tried a 9.6v 700mah rechargeable battery and the power went on for a second then stopped. It works fine when I plug it into the computer, idk if theres something im doing wrong, but i couldn't find any other way to do it. I'm thinking about buying a 2.1mm battery connector to see if that works.
is there anything else attached to your Arduino or is it just the bare board?
You should probably measure the voltage while connected to the Arduino, to make sure the battery is not dead. (Measuring the voltage while it is not connected to anything will not be accurate.)
i tried a couple of different 9v batteries and it still didn't work so i know its not the battery. I used just the bare arduino then i plugged in led and ran "blink" and still no power
i tried a couple of different 9v batteries and it still didn't work so i know its not the battery
Until you measure the loaded voltage of the batteries, you cannot make this statement. Applying 9V to Vin should work, so I would suspect the batteries you are using are near dead. Or you are connecting the battery backwards.
9Vs are lousy batteries anyway. They have very little current capacity for their size.