The massive 6510 mAh battery on the vivo X300 Pro is only half the story. The other half is how quickly you can refill it. The phone supports 90W wired FlashCharge, which uses vivo’s proprietary charging protocol to deliver massive amounts of power while managing heat efficiently.
Here is my real-world testing data on the 90W FlashCharge system.
0 to 100% Charging Test
I ran this test starting from a completely dead phone (0%) using the official 90W charger and cable included in the box. The phone was turned on immediately after plugging it in, connected to Wi-Fi, and sitting at room temperature (around 22°C / 72°F).
- 5 Minutes: 18%
- 15 Minutes: 44%
- 30 Minutes: 78%
- 42 Minutes: 100% (Full)
Considering the battery is an absolute unit at 6510 mAh, filling it completely in roughly 42 minutes is mind-blowing. A quick 15-minute splash-and-dash before leaving the house easily gives me enough juice to last an entire evening of heavy camera use.
Thermals During Charging
Heat degrades batteries over time, so how hot does the X300 Pro get at 90W? During my tests, the phone peaked at 39.5°C (103°F) around the 20-minute mark, right when it was pulling maximum wattage.
Once it hit 80%, the charging speed throttled down significantly (a standard practice to protect battery health), and the phone cooled back down to room temperature for the final 20% trickle charge. The thermal management is excellent, partly thanks to the Dimensity 9500’s efficient heat dissipation.
Compatibility with Third-Party Chargers
The 90W speed is strictly proprietary. You must use a vivo FlashCharge-compatible brick and cable to get those speeds.
If you plug the vivo X300 Pro into a standard USB Power Delivery (USB-PD) charger (like a MacBook charger or an Anker GaN brick), it defaults to a much slower standard PD rate—typically around 18W to 27W.
Pro Tip: If you travel frequently, bring the official vivo brick. Charging a 6510 mAh battery at 18W on a standard PD charger takes well over 2 hours!
See Also: Curious about how it charges without cables? Check out my 40W Wireless Charging Guide, or read my full Battery Endurance Review to see how long that 100% charge actually lasts.