I have this battery ICON with a slash through it on bottom. What does it mean ? Any link to screen interface explanations ?
It probably mean your implant have no battery left, or you have no implant. http://planetside.wikia.com/wiki/Implants
Nor should they. He linked the page so you could learn about implant system in general. The battery icon, as he said, means that your implant has run out of energy.
You can keep a bookmark to this site, it's an awesome database where you can find everything about the game.
Correction: it's a terrible misleading database that contains mostly outdated or plain wrong info. Implant page is about the only decent one. Implant is a part of your loadout, same as grenades and weapons. All players have Enhanced Targeting implant unlocked and equipped by default. You can watch Wrel's review about it here. You can see your equipped implant on the Implant loadout slot on the lower right corner (next to the button "change appearance"). You can learn how to recharge implant energy in this video, and more general information is here.
press esc > press the icon with the lightning > top right is button for energy page chargers drop once every couple of hours but you need to either click them into your energy pool or allow auto refill, you can also craft chargers from your spare implant drops (ultrachargers are the most efficient, use 1x T2 + 1x T3 for an ultra)