"Ingress portal recharge mechanics may provide some clues to how ACTIVITY_FEED_BERRY might be implemented."

#PokemonGO: First, the Ingress recharge mechanics: I've highlight key points.Resonators placed on a portal slot start with full XM reserves (the amount of XM capacity varies with resonator level).If left untouched, each resonator decays by ~15% (or 1/7th) of it's max XM capacity every 24 hours from the time it was deployed. Even though they have different Energy levels, an L1 and an L8 resonator will both die after 7 days if left untouched.Any agent of the same faction can recharge one or all resonators on a portal as long as they are within action range or they have key to that portal. Using the portal key to recharge is known as remote recharging. If you are not within the action range and do not have a key, you cannot recharge even if you can see the portal on your screen.The amount that can be recharged at one time is dependent on the agent's XM Capacity. This can range from 3000 XM for L1 to 22,000 XM for L16. The XM bar can be replenished by picking up XM off the ground, using XM cubes or recycling items. Any level agent can fully recharge a portal/resonator; it's just faster/easier to do so as your level increases.Remote recharging has a range limit and recharge effectiveness. Range efficiency starts at 100% with the 40 meter action range and scales proportionally to 50% efficiency at the max range limit. An L1 agent has a max recharge range of 250 km while an L16 agent has a limit of 4000 km.If a resonator is upgraded, the decay time is reset to the new deploy time and Energy for that resonator is 100% again.Recharging does not change the decay time. If a resonator is placed at 09:23 - Day 1 and it is fully recharged at 09:20 - Day 3, it will still decay by 15% of max XM at 09:23.An agent can receive an alert when a portal they own (the agent was the placed the first resonator on a neutral portal) is under attack (even if all his/her resonators have been upgraded) or if they have a resonator deployed on a portal they do not own AND that resonator receives any damage. You will not get attack notifications if all your resonators have been upgraded.Attack notifications are somewhat delayed and attackers can do damage faster than one person can recharge. Other than the next bullet point, there is no real active defense mechanism.Since any agent with a key can recharge a portal, mass recharging is a strategy that is used locally to keep portal farms alive and globally during anomalies using "recharge rooms". Several people recharging a portal farm will not stop the attacker(s) from killing all the portals, but it will make them use up valuable inventory much faster. In an anomaly event, groups of portals are designated ahead of the event allowing factions to farm hundreds of keys to those portals, Those keys are then distributed to groups to use for mass recharging during the event. Once a portal(s) is designated to be of high point or strategic value, the message is sent to those rooms to focus on recharging that portal(s).How this may translate to gym "recharging" mechanics. This purely speculation on my part, but it is based on the similarities and differences between Ingress and PoGo.To fix the issue of stagnant gyms, Niantic may implement an "Energy Bar" of sorts. A Pokemon on a gym would lose a percentage of max energy each day until it faints and is then returned to the owner. It could also work to have the HP stats deplete if a Pokemon is not fed, but since potions are already tied to HP, it wouldn't make sense to also attach berry feeding. It does make sense to have a stat bar that only applies to Pokemon deployed in a gym.Feeding your Pokemon a berry will recover part of it's energy and keep it active in the gym. I would imagine that a Pokemon with reduced Energy will make it weaker in battle by modifying it's attack or defense stats. A deleted energy bar might also modify it's position in the gym where an unfed Pokemon in Slot 4 would progressively move to Slot 1 until it faints completely.Since gyms have no current version of a portal key, it's likely that only the Pokemon owner will be able to "recharge" his/her own Pokemon.I don't believe that feeding Pokemon by non-owners will be implemented since there is currently little benefit to other team members by keeping a gym alive. In Ingress, all faction members benefit from keeping portals alive since portal levels determine (in part) the level of gear that an agent will get. Fully deployed portals also allow any faction agent to create links and fields to earn AP (XP). EDIT: as pointed out by /u/Kevkillerke and /u/dUbiLL, trainers may want to help friends and known teammates keep their Pokemon alive while letting spoofer Pokemon starve.While Niantic may implement gym attack notifications, they will likely be delayed and have a minimal effect on an attackers ability to defeat the gym Pokemon.Remote Feeding would likely be implemented, but it would make sense to limit the feeding (recharge) range based on trainer level. I can also see this working where you must be within action range of the gym to feed your Pokemon. This would have the effect of 1) getting trainers out and about more often and 2) limiting a spoofer's ability to place Pokemon everywhere by requiring them to spoof to every location to feed every Pokemon on a regular basis. In reality, a legit player has no need to keep more than 15 or so Pokemon on gyms (the extras to ensure max daily gym reward).Ingress does have a Recharger badge. If a similar badge was introduced to PoGo, I can see how allowing trainers to feed teammates Pokemon would be implemented. I still believe remote feeding your own 'mon while feeding other's Pokemon only within action range would be the best implementation.I may have missed some key comparing/contrasting, but this post is getting long. Hope this provides some insight into possible future game featuresEDIT: added content per comments via /r/TheSilphRoad http://ift.tt/2qTVSqX