Several different makes of ESC are in use for F5B models but you will find that a lot of people are using a slightly modified Castle Creations Phoenix 180 for it’s performance and relatively low cost. Without the modification the P125/P180 should not be used with more then 4S, after it you can safely use up to 6S. Information on how to modify these speed controllers can be found here.
It is suggested that the HK-200 controller (there are several different suppliers) is good for the first year or more. It will happily handle 4S Lipo and up to 300A without much trouble. That is 4KW right there and only for about 30-40 USD.
In the future it looks like some people will be going the HV (higher voltage) route. Since we are all limited to the same amount of Energy and essentiall also power, higher voltage means lower amps. This in turn means less heat loss from the wires between the motor, ESC and battery pack. But don’t be fooled, this is no magic efficiency gain.
Popular ESC’s in future may be the CC ICE2 160 HV and the Kontronik Jive 120+ HV. Be aware that the Kontronik is limited in the amount of time part throttle can be used.
If you want to retain flexibilty with battery choice the YGE 200HV is a good option as it works well in the 300-400A range on 4 to 6 cells, but is also OK for up to 10 cells.
These days top pilots will be using some form of thorttle management (ramp on the TX) to keep the power from going to high at the start of the climb to keep the prop from becoming stalled. When the prop starts to stall (it does not stall completely, just near the root of the blade) it makes a really impressive sound but does not really improve efficiency. Better is to save this energy for later in the climb when the model is going that much faster. This may make the difference between the top few places.
Note; For a small fee i am willing to modify the P125/P180 logic board. Having done over 200 logic boards so far. You can find me on RC Groups as ”jjmouris” or drop me an e-mail.