No, don't try to connect the battery to the i2c port. You need to connect the positive and negative wires of the battery to the barrel adapter and plug it in to the side of the EZ-B's power shell. The smaller wires on the battery are for charging the battery with a LiPo charger.

Your using the power input which is on the bottom of the stacked pcbs (mini dean connector), else you use the power base the board comes connected to. If you are not familiar with lipos please research before using them since they can be dangerous if used incorrectly. Check out the lessons for powering up your board: Lessons

How I did mine was to cut off the main connector and connect the wires to the barrel jack terminals (make sure polarity is correct), but there are adapters available too. Or you could use a mini deans connector that would connect to the EZ-B without the power base.

Quote:

I want to connect a lipo battery 7.4v to the EZ-Bv4 unluckily I don't know which port I need to use

Ways to power the board are either through the barrel connector or to connect or replace the mini dean connector. Steve G's method of just replacing the barrel connector i s probably your safest method since it will keep the fuse in line with your board.

Thanks for all of your comments it helped well

No problem. Glad the advice helped. If you find that the battery wires are too thick to go in to the barrel jack terminals, you could connect the battery wires to a terminal block, the use some thinner grade wire from the block to the jack.