#Apple macbook pro magsafe 2 85w full#

If there isn't enough power left for the charger, the battery is by definition discharging unless it has no charge left. Thus, given an available input power, the machine load is satisfied first, and any leftover power is provided to the battery charger. The power management system also knows the electronic nameplate of the power supply and thus its rated power. The loads are prioritized: the machine has priority over the battery charger. The power management must maintain the following inequality balanced, in terms of power: (power adapter + battery as a power source) >= (battery charger + the machine). The battery as a power source is exclusive of the battery charger: a battery may operate as a power source, or the battery charger may operate, but never both at once. the machine (logic, drives, memory, screen, speakers, USB devices, etc.)īoth loads are adjustable and the power management's function is to adjust them as needed.

The below explains why.Ī MacBook's power management works very simply: it maintains a balance of power between the power consumed by the loads and the power available from the sources. It will operate safely, but the CPU performance will be diminshed. The MacBook it's plugged into won't operate in a 'brownout'.

#Apple macbook pro magsafe 2 85w full#

It will clearly run at full capacity for longer than a higher wattage adapter or even fail to keep up with the energy demands of a machine using more than 60w giving you a flat battery if you run a deficit of energy “while charging”. So no, a 60W adapter won't overheat when connected to a machine that needs an 85W adapter. This is a given for the systems to receive safety certifications. I will give some facts along with my reasoning.Īll MagSafe adapters, when plugged into a mechanically matching receptacle on a MacBook/MacBook Pro, are designed to run safely. There is a lot of misinformation in some answers.