Only if you choose to limit yourself to StVZO-legal taillights... Pretty sure there are powerful ebike rear lights these days that might not be strictly Germany-legal but can be found in other places - and various converters with different output voltages (mine does 5V and 12V, others vary). (Apologies to the one person on this thread who is in Germany...) But yeah, as for me I use a battery rear flasher and a dyno-charged cache battery