After the completion of our measurements we can complement the official information from Microsoft. Our Reader's Test (reading of a text file) with the minimum display brightness and deactivated wireless modules determined a maximum runtime of more than 13 hours. Our script in the WLAN browsing test (v1.3) ran for more than 7 hours with an adjusted brightness (177 cd/m², maximum brightness minus 4 steps). The Surface 3 was empty after around 3 hours under load (Classic test). These runtimes are okay for a device that is mainly designed for simple tasks and web browsing, and the same applies for the comparison with other convertibles. Despite the more powerful CPU, the Surface Pro 3 manages better results in the idle test, but falls behind under load. The Aspire Switch 10 (Atom Z3735F) reaches similar runtimes in the practical WLAN test, despite the smaller battery.

"Mobile employees" in particular are the target audience for the Surface 3 according to Microsoft. For us, this means a frequent switching between battery and mains operation, depending on the environment when you use the Surface 3 on the road. And this might actually be the biggest issue of the Surface 3. The poor charging times disqualify the device as an ultramobile working device.

If you charge the device when it is turned off, the 13-Watt power adapter charges the battery by 32% (start at 5% remaining capacity) within one hour. After two hours we get 72 %, but the whole capacity of 28 Wh is only available after almost 4 hours. If you have to use the device while you charge it, however, on the train or a plane, for example, then it takes much longer. It seems that the 13-Watt power adapter is not powerful enough. We simulate the use with the help of our WLAN script and charge the battery at the same time. After one hour (once again start at 5 % remaining capacity) the battery capacity is only at 18%, after 2 hours 27%, 3h: 39%, 4h: 53%, 5h: 67%, 6h: 80%, 7h: 92%, and the full capacity is only available after around 8 hours.

In our test with multiple days of flights and numerous location changes we always had the problem that the device did not get enough power in the charging periods to use the device without a socket afterwards for a longer time.

The cable of the provided power adapter can also be used as a USB cable. The charging via USB port is basically possible, but only when the Surface 3 is turned off, otherwise the device will consume too much power so it would take quite a while.