The short answer is yes, wireless chargers are designed to stop charging once the device is fully charged. However, how this works depends on the specific charger and device combination.
How wireless charging works
Wireless charging, also known as inductive charging, uses electromagnetic induction to transfer energy between two objects – a charging pad or stand and a receiver built into the device. An induction coil in the charger creates an alternating electromagnetic field, which induces a current in the device’s receiver coil to charge the battery.
This wireless energy transfer only happens when the device is close enough to the charging pad – usually within a few millimeters. The electromagnetic field diminishes rapidly with distance, so the phone won’t charge if it’s too far away or misaligned with the charging pad.
Charging modes
Most wireless chargers and mobile devices support two charging modes that impact charging behavior:
- Transmit mode – The charger transmits power at full strength regardless of the charge level. The device controls when to stop taking in more power.
- Receive mode – The charger varies power transmission based on communication from the device about its charge level.
In transmit mode, the charger will keep transmitting at full power even after the device is fully charged. This can lead to overcharging and excess heat if left charging for too long. Receive mode allows more precise control of charging current tailored to the device’s needs.
How devices regulate charging
Mobile devices have their own circuitry and logic boards that control how much power goes into the battery when charging. There are a few key ways this is regulated:
- Charge termination – The device monitors battery voltage and stops charging once a certain threshold is reached, indicating full capacity.
- Trickle charging – Once full, some devices switch to a very slow trickle charge to maintain battery percentage.
- Battery management system – Smart circuitry prevents overcharging and damage from factors like heat, current flow, and voltage spikes.
With these protections in place, most modern devices are designed to stop absorbing charge from a wireless charger when the battery is full. This happens even in transmit mode, but receive mode further optimizes based on direct communication between charger and device.
Do wireless chargers ever stop on their own?
Whether the wireless charger itself stops transmitting power when the device is fully charged depends on the mode it’s operating in:
- Transmit mode – The charger will keep transmitting at full strength indefinitely, relying on the device to regulate charging. It does not stop on its own.
- Receive mode – The charger will dynamically adjust power output based on charge status communication from the device and stop transmission when the device reports full capacity.
So in receive mode, the charger can stop on its own but in transmit mode it keeps going – the device has to regulate absorbing additional charge.
Charging scenarios
Here are some common charging scenarios and how the charger and device behave when the battery is full:
Charging phone in transmit mode
- Charger transmits at full power even after phone battery reaches 100%
- Phone charge management system stops taking in charge when full
- Excess power transmitted by the charger is wasted
Charging earbuds in receive mode
- Earbuds communicate charge level to the charger as it fills
- Charger dynamically reduces power transmission as battery reaches capacity
- Charger stops transmission when earbuds report completely full battery
Leaving phone on transmit mode charger overnight
- Phone stops charging once full
- Charger keeps transmitting power all night, which is wasted
- Long term overcharging and heat generation can degrade battery
The takeaway is that receive mode is better at maximizing efficiency and preventing overcharging, while transmit mode relies entirely on the device to regulate how much power it takes in.
Other charging considerations
There are a few other factors to keep in mind around wireless charging and battery capacity:
- Heat – Charging generates heat, which can degrade batteries over time. Give devices breaks from charging to dissipate heat.
- Alignment – The closer to perfect alignment between charger and device, the more efficient power transfer is.
- Case compatibility – Charging cases need to be designed to work with wireless charging for the best experience.
- Software – Fully updating your phone’s operating system ensures the latest charging software/firmware.
Using wireless power sharing
Some Samsung phones also have a wireless power sharing feature that lets you charge another device directly from the phone’s battery. For example, you can charge Galaxy Buds earbuds by placing them on the back of a recent Galaxy S smartphone.
Wireless power sharing typically works by amplifying the device’s existing wireless charging receiver coil to emit a chargeable electromagnetic field. The phone becomes the wireless “charger” for the buds or other devices.
Like with dedicated wireless chargers, power sharing will stop charging the connected accessories once their batteries are full. The phone determines this by communicating directly with the powered devices to monitor their charge status.
Wireless power sharing does drain the phone’s battery much faster, since it’s now supplying the charge instead of plugging into a wall outlet. So it’s best used in a pinch for giving your earbuds or watch just enough juice to last a while longer.
Wireless charging car mounts
Another popular accessory that leverages wireless charging is the car phone mount. These mounts allow you to secure your smartphone in your car’s cabin and charge it wirelessly at the same time.
Wireless charging car mounts work the same as any Qi standard wireless charger. They contain induction coils to transmit power to a device’s receiver coil when mounted. The phone sits in a cradle against the charging surface.
These mounts are designed with transmit mode in mind. The charger coil continuously outputs power at the full rate. The phone takes over regulating when to stop taking in more electricity once its battery fills.
Induction-based wireless charging is actually an ideal setup for in-car use. The charger can provide consistent power whenever the phone is mounted for navigation, music playback, etc. And the device seamlessly starts and stops charging as needed without any user intervention.
Choosing a car wireless charger
Here are some factors to consider when selecting a wireless charging car mount:
- Mount style – Dashboard mounts, vent mounts, windshield mounts, etc. Pick one that works best in your car interior.
- Phone case compatibility – Ensure the cradle can fit your phone with the case on.
- Clamp strength – The mount should have a solid grip to withstand vibration and bumps in the car.
- Charging power – 10W output or higher provides the fastest charging speed.
- Safety – Check that the mount doesn’t obstruct visibility or interfere with airbag deployment.
Following car mount safety and local regulations is important, since placing a mount incorrectly can become a driving hazard.
The wireless-charging technology will continue evolving, current standards already allow safe, hassle-free charging just by placing our devices on a surface. Understanding how wireless chargers actually work helps ensure you’re charging properly and getting the most out of the technology.
