Cooling Fan Overview: Hobbywing AXE 2510BH-6V Cooling Fan. This replacement cooling fan is intended for popular Hobbywing ESCs (Electronic Speed Controllers). Package includes one cooling fan. NOTE: Please choose the correct cooling fans for different applications. For 4-6 cell NiMH or 2S LiPo: No need to change the 5V cooling fan on the ESC For 7-9 cell NiMH or 3S LiPo: Please choose a 12V cooling fan or supply the 5V fan from the receiver (+6V) For 10-12 cell NiMH or 4S LiPo: Please choose a 12V cooling fan, and cut the output of the built-in BEC. Then supply the receiver with a UBEC (An additional external DC-DC regulator) Compatible ESC: AXE R2 ESC