Today, Microsoft has released a final battery update for Microsoft Surface Pro 3 after the Surface team has completed their internal testing of the update. This update seems to be a fix for your Surface Pro 3 after a long waiting. This new update will bring your Surface Pro 3 firmware up to the version of 38.10.90.0.

Here is the information that has been announced in Microsoft Community page:

Hello everyone,

Thanks for your continued patience here. We have now completed our testing of the update and it has passed our quality assurance process.

The update, “System Firmware Update – 8/29/2016”, is now available to install from Windows Update.

Before installing this update, ensure that your Surface Pro 3 is plugged directly in to AC power using the standard AC power adapter (do
not use the Surface Docking Station), disconnect any USB devices or external monitors, and check that Windows shows a 40% charge or greater when you hover over the icon in the taskbar before you begin.

Once you install the update, please select Restart now (do not shutdown). After your Surface restarts, please manually restart it a second
time to complete the process. For more information, please see our
Surface Pro 3 Battery FAQ article.