Possible firmware/power-state issue: Flex Keyboard drains ~5%/hour after shutdown on Surface Pro for Business 12th Edition Intel, but only ~1%/hour on 11th Edition Inte

Question

Possible Surface Pro for Business 12th Edition Intel firmware / accessory power-state issue with Surface Pro Flex Keyboard

I would like to report a reproducible battery-drain issue involving the Surface Pro 13-inch Flex Keyboard when attached to a Surface Pro for Business 13-inch 12th Edition with Intel.

I initially suspected the Flex Keyboard itself, the Slim Pen 2 charging tray, Bluetooth, or motion while carrying the device. However, I have now performed a direct A/B comparison using the same Flex Keyboard and the same Surface Slim Pen 2 on two different Surface Pro generations, and the results strongly suggest that the host device may be affecting the Flex Keyboard’s power state after shutdown.

Test equipment

• Surface Pro for Business 13-inch 12th Edition with Intel
• Surface Pro for Business 11th Edition with Intel
• The same physical Surface Pro 13-inch Flex Keyboard
• The same physical Surface Slim Pen 2
• Both Surface devices and the Flex Keyboard are fully updated through Windows Update / Surface app
• Flex Keyboard was physically attached to the Surface in both tests
• Slim Pen 2 remained in the Flex Keyboard charging tray in both tests
• Both Surface devices were shut down manually using Start > Power > Shut down

Test 1 — Surface Pro for Business 12th Edition Intel

The device was essentially stationary overnight.

• 22:22 — Surface battery: 43%; Flex Keyboard: 45%
• 06:12 — Surface battery: 41%; Flex Keyboard: 5%
• Elapsed time: approximately 7 hours 50 minutes
• Flex Keyboard battery loss: 40 percentage points
• Average Flex battery drain: approximately 5.1% per hour

Bluetooth had been manually disabled before shutdown.

This was not an isolated observation. In an earlier test on the same Surface Pro 12th Edition Intel, the Flex Keyboard dropped from 80% to 58% in approximately 3 hours 46 minutes, equivalent to approximately 5.8% per hour.

The similarity between the two drain rates is notable:

• Test A: approximately 5.8%/hour
• Test B: approximately 5.1%/hour

The second test was essentially stationary, so normal commuting vibration or motion does not appear to be required to reproduce the high drain.

Test 2 — Surface Pro for Business 11th Edition Intel

I then moved the exact same Flex Keyboard and Slim Pen 2 to a Surface Pro for Business 11th Edition Intel.

Conditions were otherwise kept the same:

• Same Flex Keyboard
• Same Slim Pen 2
• Pen remained in the charging tray
• Keyboard remained physically attached
• Surface was shut down using Start > Power > Shut down
• Device remained stationary

Results:

• 09:12 — Surface battery: 80%; Flex Keyboard: 80%; Slim Pen 2: 99%
• 11:13 — Surface battery: 80%; Flex Keyboard: 78%; Slim Pen 2: 99%
• Elapsed time: approximately 2 hours 1 minute
• Flex Keyboard battery loss: 2 percentage points
• Average drain: approximately 1% per hour

Bluetooth was not manually disabled on the Surface Pro 11 before shutdown.

Therefore, despite Bluetooth being left enabled before shutdown on the 11th Edition, the Flex Keyboard drain was approximately one fifth of the drain observed on the 12th Edition Intel.

Why I believe this may warrant engineering investigation

The same Flex Keyboard and the same Slim Pen 2 behave very differently depending on which Surface Pro host they are attached to.

This makes the following explanations less likely:

• Flex Keyboard battery-cell self-discharge
• A defective Slim Pen 2
• Normal Slim Pen charging consumption
• Bluetooth activity alone
• Movement or vibration alone

A possible explanation is that the Surface Pro for Business 12th Edition Intel is leaving the Flex Keyboard in a higher-power accessory state after Windows shutdown, instead of allowing it to enter its normal low-power state.

I am not claiming that this has been proven to be a driver or firmware bug. However, the cross-platform comparison suggests that it would be useful for the Surface engineering team to investigate the shutdown interaction between the 12th Edition Intel platform and the Flex Keyboard.

Relevant components may include, for example:

• Surface System Aggregator
• Microsoft Accessory Firmware
• Surface Type Cover v7 firmware
• Surface Integration / Surface Integration Service
• UEFI / embedded-controller power-state handling
• Flex Keyboard / Slim Pen charging-state handling

Microsoft’s official Surface Pro 12th Edition Intel update history shows that several of these components are platform-specific and have already received firmware/driver updates.

What I would like Microsoft to check

1. Whether the Surface Pro for Business 12th Edition Intel correctly sends the expected low-power/shutdown state to an attached Flex Keyboard.
2. Whether the Flex Keyboard remains in an active or intermediate power state after shutdown on this platform.
3. Whether the Slim Pen charging/detection subsystem remains powered after the host has shut down.
4. Whether this can be reproduced internally using the same Flex Keyboard on an 11th Edition Intel and a 12th Edition Intel Surface Pro.
5. Whether a Surface System Aggregator, Accessory Firmware, Type Cover firmware, UEFI, or other platform firmware update is required.

I can provide screenshots showing the battery percentages and timestamps for both platforms, and I am willing to perform additional controlled tests if the Surface engineering team needs specific data.

Thank you.

[Moderator's note: Duplication removed]

Answer 1

Thank you for sharing such a detailed analysis, Jeff Z.

I can see you've already performed far more extensive investigation than most users would typically do, and your results showed a significant host-dependent difference in the keyboard’s battery drain after shutdown. However, they cannot confirm a firmware defect or identify the cause yet.

In addition, since Microsoft Q&A is a user-to-user support forum, contributors here do not have access to the internal diagnostic or engineering systems needed to validate your theory or escalate the issue directly to the Surface engineering team. Given those limitations, I recommend submitting the findings through an official Microsoft channel:

• Since you're using a Surface Pro for Business model (11th - 12th), if it's owned or managed by an organization:
  • Refer to: Contact Surface Support for Business and Education customers | Microsoft Learn 
  • Submit your case through the Microsoft's Surface Support Portal.
• If this is a personally owned device, use the regular Surface support channel instead:
  • Visit Contact Us - Microsoft Support > Sign in  
  • Enter / choose an issue > Get Help to make request  
  • Scroll down > click Contact Support to connect to an agent 
  • Select a category > continue and you should reach the chat option. 
  • If you don't see it, go through another category (e.g. Billings and payments...)

Note: The support contact team only works at certain times, so if the last window shows that it's unavailable, try opening it again the next day. If you prefer phone support, you can leave a phone number. This way, they can call you and help you.

• You can verify the keyboard’s installed firmware in Surface app > Keyboard > Firmware Update.
• Include in the report all the details you shared above, including versions of drivers, Windows, devices...

While posting here may help attract others who have observed similar behavior, it is unlikely that the thread itself will be reviewed by the engineering team. Since you already have multiple a reliable repro, this should be useful for investigation if submitted through the correct channel.