Reverse wireless charging is a feature that lets one smartphone transfer power wirelessly to another compatible device. Instead of receiving energy from a charging pad, the phone acts as the charging pad.
You place a Qi-compatible device, such as wireless earbuds or another smartphone, on the back of the phone providing power. The phone's internal charging coil sends energy to the receiving device through magnetic induction. The Wireless Power Consortium's Qi 1.3 introduction explains the underlying charging system.
Reverse Wireless Charging at a Glance
| Feature | Explanation |
|---|---|
| Also called | Wireless PowerShare, Battery Share or reverse charging |
| Main purpose | Charge small devices when you do not have a separate charger |
| How it works | One phone becomes a Qi wireless power transmitter |
| Devices it can charge | Compatible smartphones, wireless earbuds and selected wearables |
| Main limitation | It is slower and less efficient than wired charging |
| What it requires | A phone with reverse wireless charging and a Qi-compatible receiving device |
How Does Reverse Wireless Charging Work?
Reverse wireless charging uses the same basic technology as ordinary Qi wireless charging, but the two devices swap roles.
- The phone activates its internal wireless charging coil.
- The coil creates a changing magnetic field.
- The receiving device detects the field through its own coil.
- The receiving device converts that energy into electrical power for its battery.
The Wireless Power Consortium describes Qi charging as magnetic induction between a power transmitter and a power receiver. With reverse wireless charging, the smartphone becomes the transmitter.
What Can Reverse Wireless Charging Charge?
Reverse wireless charging can usually charge:
- Qi-compatible smartphones
- Wireless earbuds with a Qi-compatible charging case
- Selected smartwatches and other wearable devices
- Small accessories that support Qi wireless charging
Compatibility depends on both devices. Samsung states that Wireless PowerShare supports Qi-certified smartphones and selected Samsung wearable devices. Google's Battery Share supports Qi-certified phones and accessories such as Pixel Buds.
The receiving device must support Qi wireless charging. Bluetooth compatibility alone is not enough.
How Do You Use Reverse Wireless Charging?
The steps depend on the phone manufacturer and model.
On Samsung Galaxy Phones
Samsung calls the feature Wireless PowerShare:
- Open the Quick Settings panel.
- Select Wireless PowerShare.
- Place the receiving device on the back of the Galaxy phone.
- Align the charging coils and wait for charging to begin.
Samsung advises against charging the power-sharing phone at the same time. Doing so may reduce charging speed or cause charging problems.
On Google Pixel Phones
Google calls the feature Battery Share:
- Open Settings.
- Tap Battery.
- Select Battery Share.
- Place the Qi-compatible device on the back of the Pixel phone.
Google's Battery Share can stop when the receiving device is fully charged, the phone becomes too hot, the devices are poorly aligned or the phone reaches its selected battery limit.
Is Reverse Wireless Charging Fast?
No. Reverse wireless charging is mainly an emergency or convenience feature, not a replacement for a wired charger.
Charging speed depends on:
- The speed supported by both devices
- The distance between the charging coils
- Phone alignment
- Case thickness
- Temperature
- The battery level of the phone providing power
- Energy lost during wireless transmission
Wireless charging already loses some energy compared with a direct cable connection. Reverse wireless charging also draws power from the host phone, so the receiving device gets only part of the energy taken from the host phone's battery. Google warns that Battery Share can significantly reduce Pixel battery life while it is running.
What Are the Advantages?
Reverse wireless charging is useful when:
- Your wireless earbuds are nearly empty
- You need a small emergency charge on another phone
- You forgot a charging cable
- You are travelling with minimal accessories
- You want to charge a Qi-compatible accessory from your phone
The main benefit is convenience. One device can provide limited power to another without a separate charging pad, cable or wall adapter.
What Are the Disadvantages?
The main drawbacks are:
- It drains the phone providing the power.
- Charging is usually slower than using a cable.
- Wireless energy transfer creates extra heat.
- The devices must stay correctly aligned.
- Thick, metallic or magnetic cases can interrupt charging.
- The feature may stop if the phone gets too hot or the connection becomes inefficient.
- Not every smartphone supports reverse wireless charging.
Google notes that cases, poor placement and temperature can affect charging performance. Battery Share can also turn off when the phone detects inefficient power transmission.
Does Reverse Wireless Charging Damage the Battery?
Occasional use should not normally damage a phone battery, but it increases battery usage and can create heat.
Heat, repeated charging and discharging, battery age and usage patterns all affect battery capacity over time. Google identifies temperature and charging behaviour as factors in battery degradation.
For regular charging, a wired charger or dedicated wireless charging pad is more practical. Reverse wireless charging is better suited to short, occasional top-ups.
Reverse Wireless Charging vs Wired Reverse Charging
| Type | How it works | Best for |
|---|---|---|
| Reverse wireless charging | The phone transfers power through Qi magnetic induction | Charging earbuds or another phone without a cable |
| Wired reverse charging | A phone sends power through a USB cable | Faster emergency charging and better energy efficiency |
| Standard wireless charging | A charging pad sends power to the phone | Convenient everyday charging |
| Standard wired charging | A cable connects the phone to a power adapter | Fast and reliable charging |
Does Every Phone Support Reverse Wireless Charging?
No. Reverse wireless charging requires support from the phone's hardware and software, so availability varies by model.
Check the phone's specifications or settings for names such as:
- Wireless PowerShare
- Battery Share
- Reverse wireless charging
- Reverse charging
- Wireless power sharing
The receiving device must also support Qi wireless charging. A phone may support ordinary wireless charging without being able to charge another device wirelessly.
Bottom Line
Reverse wireless charging turns a compatible smartphone into a small wireless charging pad. It works best for short emergency charges on wireless earbuds, smart accessories or another Qi-compatible phone.
The trade-off is slower charging and a lower battery level on the phone providing the power. It is a useful backup feature, not a replacement for a cable or charging pad.