Änderungen

'''So no worry of proper shutdown anymore - just unplug it or operate the main power switch and the Raspberry will detect it and shutdowns nicelywhile the supercapacitors provide the power for this time.'''

It works pretty well but those big caps are expensive if you have to buy them. It could be done much better and with much smaller supercaps if a step-up-converter or even better a step-up-and-down-converter is used to generate the 5V or better directly the . The Raspberry uses a very unefficient linear regulator for 3.3V by default - by changing that to a switched-one the holdup time can be increased also. As most things on the Raspberry only needs (avoiding will operate on 3.3V supply, it does not matter much that power-wasting linear regulatorthe 5V is just 4.5V or even lower as it will be the case with this very simple circuit. But beware, devices on USB port (especially WLAN adapters)may really want nearly full 5V for proper operation...