Recharging

There are different ways Resonators  and in turn the Portals they are associated with can lose power.
All Portals lose some of their energy (in the form of XM) on a daily basis for example, which is known as decay. In the process each Resonator  on the Portal loses exactly 15% of their maximum charge until they have no XM left and disintegrate as a result, eventually returning the Portal to a neutral state. To prevent this Agents have to recharge the Portal's Resonators  regularly by infusing them with XM from their own storage and are awarded 1 AP/100 XM recharged (rounded down, but at least 1 AP per recharge).
Resonators  also lose some of their charge when subjected to special XM-Pulses as emitted by XMP Bursters  and Ultra Strikes . If a Portal is under attack by such Weapons Agents can also recharge the Portal by continuously pumping XM back into its Resonators  to counteract the losses and prevent the Resonators  from being destroyed.
This can be done either directly by getting in close enough proximity to the Portal for it to be in the Agent's action radius, or remotely via a Portal Key . The distance at which an Agent can recharge a Portal remotely is determined by the Agent's Level and ranges from 250km at Level 1​ to 4 000km for L16 Agents (See: Recharge Ranges) but the recharge efficiency drops at increasing ranges.

There are different options for how to recharge Portals:

•		: Increases a single Resonator's  charge by up to 1 000 XM.1
•		: Increases a single Resonator's  charge until it is full or the Agent's XM storage empty.
•		: Increases all remaining2 Resonators'  charge equally by up to 1 000 XM1 combined.
•		: Increases all remaining2 Resonators'  charge equally until the Agent's XM storage is empty.
1 Depending on the recharge efficiency and Resonator's charge. 2 Only the charge of Resonators which are not already at full power will be increased.

Recharge buttons
Recharging options

Recharging attacked Portals

Recharging Portals remotely may need some planning:

• if the Portal is of high level, you will probably need Power Cubes  to recharge yourself in case of attack;
• if the Attacker is powerful, you may need to predict their arrival before they attack or you will not charge quickly enough;
• in any case the alerts will give you a quick link to the Portal recharge (you only need to wait for a fix to the Portal), but that is useful only if you have a Portal Key .

Finding Portals to recharge

The easiest way known so far is to click OPS > Inventory > Portal Keys, then browse the Portal Keys  and, when you see one for a Portal of your faction, check whether the energy bars of the respective Resonators  are full. If not, just tap twice and you will be able to recharge. This process is rather tedious but comprehensive.

Medals

Main article: Recharger

The following Medals can be earned by recharging a certain amount of Portals' XM:

Bronze	Silver	Gold	Platinum	Onyx
100 000	1 000 000	3 000 000	10 000 000	25 000 000

Most Agents will agree that Recharger is the easiest Onyx/Black medal to achieve, as Agents typically receive a surplus of Power Cubes  from hacking.

Recharging efficiency

Each single recharge costs the Agent 1 000 XM (unless the recharged Portal needs <1 000 XM to a full charge) the Portal charge however does not always increase by an equal amount. There are multiple factors which play into the recharging efficiency, the most obvious and well known one being the Range efficiency which is displayed in the recharging interface. Interestingly the usage of a Portal Key  also effects the recharging efficiency. The only way to recharge a Portal by the full 1 000 XM and thus getting the recharging efficiency truly to 100.0% is by recharging the Portal on location without having an active Portal Key  of said Portal in one's inventory. If a Portal Key  is used for recharging or even if the Portal is recharged on location but there is an active Portal Key  of it in one's inventory the recharging efficiency drops (independently from the Range efficiency) to 99.2% and the Portal is only recharged by 992 XM.

The recharging efficiency can be calculated as follows:

$\mbox{(Displayed) Range efficiency} = 1 - {\mbox{Distance in meters} \over (500 000 \times \mbox{Agent Level})}$

${\mbox{Recharging efficiency}}=(0.996+(0.004\times \pm 100.0\%{\mbox{ Range efficiency}}))-{{\mbox{Distance in meters}} \over (500000\times {\mbox{Agent Level}})}$

Recharging with =100.0% range efficiency: 100.0% Range efficiency = 1
Recharging with <100.0% range efficiency: 100.0% Range efficiency = 0
(In the formula 100.0% Range efficiency is negative if you have an active Portal Key  of the Portal in your inventory and positive if you do not and recharge directly on location.)