Microsoft will fix an issue causing some Surface Pro 4 and Surface Book units to chew through power in sleep mode. But don't expect a fix before the holidays. By Liam Tung | December 7, 2015 -- 12:42 GMT (04:42 PST) Microsoft is aware of the problem of battery drain in sleep mode and is already working on a fix. Image: Microsoft Microsoft continues to face teething problems with its flagship Surface Pro 4 and Surface Book, with the latest set of complaints directed at some units draining battery in sleep mode, rendering the Windows 10 workhorse two-in-ones less suitable as primary work devices. Postings on Microsoft's forums indicate the issue isn't trivial, particularly for road warriors who need to put their machine in sleep mode during travel. As one Surface Pro 4 owner complained over the weekend, his device's battery charge dropped from full to 72 percent after just three hours in sleep mode. "My Surface Pro 2 sipped battery compared to my Surface Pro 4 in sleep mode," the user wrote. "I can't use it for work if it's going to die on me in my bag or on my desk throughout the day with minimal use... I still have about 15 more days to decide if I'm going to keep it," the user noted. The good news is that Microsoft is aware of the problem and is already working on a fix. Unfortunately for anyone who is relying on the Surface Pro 4 as their primary work device, Microsoft does not expect the fix to arrive until some time early next year, according to a member of Microsoft support staff called Joe. The issue, according to Joe, is that the Widows 10 Surface Pro 4 isn't in as deep a sleep as it could be -- an issue Microsoft was aware of before it released the device. "We couldn't do it at [release to manufacturer] for a variety of reasons. Power management is a very hard computer science problem to solve especially with new silicon. Currently it is not in the deepest 'sleep' that it can be so there are wake events that would not otherwise wake it. We will have an update for this issue sometime soon in the new year," said Joe. However, there are several actions that can minimise the impact of the bug. To make it 'sip' power as the Surface Pro 2 did, users can adjust settings on the Surface Pro 4 and Surface Book to put the device into hibernate mode rather than sleep mode. But hibernate mode puts the device into a deeper sleep and it will not listen for signals to wake up. Additionally, users should ensure Microsoft's Edge browser isn't actively streaming video or music from a website when closing the cover and putting the device to sleep. Windows Central, which first reported the forthcoming fix, noted that Edge can keep sites active in the background in standby and does the same on Microsoft's Windows 10 Mobile Lumia 950 and Lumia 950 XL, which can explain battery drain issues on those devices. Despite the workarounds, Surface Pro 4 and Surface Book buyers who took a chance on Microsoft's pricey flagships are unlikely to be pleased that the brand-new hardware doesn't live up to expectations.