Having a Portal Key in your inventory allows you to remotely recharge Resonators deployed on that Portal. Portal Keys can be obtained by hacking Portals.
The efficacy of a remote recharge depends on your physical distance to the Target Portal. The closer you are to a Portal and its Resonators, the less XM it will cost to recharge. Note that your remote recharge range and your XM tank capacity will increase as you level up.
How to Recharge
- On the Map screen, tap the Main menu button, then tap Inventory
- Tap or swipe to the Portal Keys tab
- Select a friendly Portal that needs recharging, then tap Charge
- Tap Charge All or Boost Charge All to recharge the Portal