For Smart Devices
Get the most out of your smart devices With TeckNet's BLUETEK Technology, each Smart USB Port independently scans your smart device (phone, tablet etc) as it's plugged in and then configures itself to match the device's specific charging profile.
TeckNet BLUETEK optimises the charge capacity for each Smart USB Port and ensures that your device recharges at the maximum speed (up to 2.4A) - up to 14% faster than traditional 2.1A USB chargers. As a result, your device will be charged efficiently and at the maximum speed possible
TeckNet BLUETEK Technology automatically adjusts the output level to any device it’s connected to. This means you can easily and efficiently charge smartphones and tablets from Apple, Samsung, HTC, Google and BlackBerry, as well as a variety of digital cameras and handheld gaming devices
S0, just taking a guess... Maybe after about 30 secs it realises the power demand is kicking in and takes time out to 'optimise' itself. If it is being used as a charger there would be no visible impact of dropping its output for a while as it adjusts. But if it is being used as a power supply that would be fatal. As I say, nothing more than a guess. But it would explain the behaviour you are seeing. You would need some sort of monitoring like an oscilloscope be be sure. Or you could try asking the vendor if this is the way the Bluetek technology is expected to work.
[But to be clear: I have never used one of these devices myself so all the above is theoretical... ]