Hi all,
I have been using these ,
To run led lights from a 12v battery at 1.2A, charge batteries at 1.5A as a DC-DC charger and run the Arduino Uno (for a short time).
They seem stable and cant beat the price.
Specs for the one i use,
Converter XL6009 ModuleAT30
ModuleProduct parameters：
Input voltage: 4-30V
Output voltage: 0.5-30V
Output current: 3A, 4A with cooling fan
Output power: 30W without cooling fan,60W with cooling fan
Output ripple: 30MV (Full output voltage)
Conversion efficiency: Boost, 88%-91%; Buck,87%-90%.
Short circuit protection: Yes
Working frequency: 180KHz
Size: 482321mm
To work out the wattage you use highest input/output voltage minus the lowest input/output voltage times the current.
So 6v in minus 5v out times 1A = 1watt (rule of thumb)
Or 12v out minus 6v in times 2A = 12watts
Worth a look.
Daz