Gaming/normal computing on laptop then "sleeps" very adruptly.

The event log entry “The system is entering sleep. Sleep reason: Battery” indicates Windows believes a battery-related condition requires entering a sleep state, even if the device is plugged in and shows 100%.

On Windows systems, sleep is controlled by power policies and system sleep criteria:

• Windows can enter sleep automatically based on power conditions and configured policies, not only on user action. When power is low, an application or the system can request that the system suspend itself using the same mechanisms used for normal sleep transitions.
• Before entering sleep, Windows determines the appropriate sleep state (S1–S3 or Modern Standby) based on hardware support and power policy, then transitions into that state. In S1–S3, the system appears off but retains memory and can wake from input or wake events.
• The “Battery” sleep reason typically means Windows detected a battery/power status change that matched a policy condition (for example, a threshold or a perceived low/critical battery state), and therefore initiated sleep.

Given that the laptop is plugged in and not overheating, likely causes include:

1. A transient or incorrect battery/power reading causing Windows to think the battery dropped or changed state unexpectedly.
2. A power policy or battery threshold that is being triggered incorrectly.
3. A brief loss or fluctuation of AC power where the system falls back to battery and immediately applies a battery-based sleep rule.

Relevant behavior from Windows power management:

• When entering sleep, Windows preserves system and application state automatically; most applications do not need to do anything special. The system sends a suspend notification (PBT_APMSUSPEND) and then transitions to the selected sleep state.
• Sleep state selection (S1–S3 or Modern Standby) and when to enter sleep are driven by criteria such as user activity, application activity, and power settings configured on the Power & sleep page.

Practical steps based on this behavior:

1. Review and adjust power settings
   • In Windows Settings → System → Power & sleep, check the timeouts for “On battery” and “Plugged in” and ensure they are not set too aggressively.
   • Confirm that no custom power plan or OEM tool is configured to force sleep on certain battery percentages.
2. Check for battery/power anomalies
   • Monitor whether the battery icon or charge percentage flickers or briefly shows a drop when the issue occurs, which would indicate a hardware or connector issue.
3. Verify sleep state behavior
   • Use powercfg /a in a command prompt to see which sleep states are available. This helps understand whether the system is using classic S1–S3 or Modern Standby, which can influence how quickly and under what conditions it sleeps.

If the behavior persists, it points either to:

• A hardware/power issue (battery, DC jack, or power circuitry intermittently reporting a bad state), or
• An OEM-specific power management feature misinterpreting battery conditions.

In that case, updating system BIOS/firmware and OEM power utilities, or having the battery/power hardware checked by the manufacturer, would be appropriate next steps.

References:

• System Sleep Criteria
• System power states
• System Sleeping States