He he! I was waiting for something like this JB👍
#1 "(especially with brushed motors- 15A seems excessive)"
Let's get this out the way straight away. The question here is 3 Brushless on one channel.
As an aside here; I haven't yet needed more than 8Amps to get a 2kg boat on the plane and zipping around for an hour or so😊
#2 "ESCs can't recognize cell numbers as the balance leads are not connected."
"if you use NiMh the ESC can only read the voltage coming in and it is impossible for it to read cell numbers."
Agreed JB. The ESC can't 'count' cells, it can only estimate them from the voltage applied.
BUT! As I said; it is easy to fool the ESCs. Set the wrong battery type and the ESC will react wrong. That's why I stressed setting each parameter manually: battery type and number of cells or nominal voltage.
You have previously set the ESC to run with an NiMh battery, with or without specifying the cell number., and connect a fully charged NiMh battery with ~7.6V. The ESC recognises that as a 6 cell NiMh, nominal 7.2V, and sets an appropriate Cut Off of 1.1V. So far so good.
You zip happily round the lake till the performance wanes and come in for a battery change.
You connect a fully charged 2S LiPo with an O/C voltage of ~7.8V. But forget to change the ESC setting to LiPo. The ESC recognises the 2S LiPo as a 6 cell NiMh and sets the Cut Off to 1.1V!!
Result: the ESC will let you thrash round the lake until the LiPo is discharged to destruction; i.e. well below the 3.0V minimum.
The other way around; LiPo before NiMh - the ESC will spoil your fun well before the NiMh is depleted🤔
I agree with you JB that many folks fit overpowered motors and/or props that are much too large diameter (and/or pitch) for the motor.
That only contributes to excessive current drain without any increase in performance.
"My airboat has a 3648 1450kv outrunner on a 3s 4000mAh LiPo but I'm only using a small 9x6 - (around 30A max) prop to stop it getting hot. If I use a 4s I'd have to go down to around an 8x6, ( a 9x6 on 4s draws around 62A -700W and gets hot) This motor is capable of 1600w on a 6s but would only be used in a 90mm ducted fan at that. Its max efficiency is only 45-50A (taken with a grain of salt) Bit of a convoluted way of making a point, but it is 9.24AM and it's time for bed😂"
All very good advice for an Airboat with with corresponding airscrew JB.
But I see your point and it's loosely translatable to boats and water screws.
I.e. Bigger is not always better!
BTW: I have not yet 🤞 managed to overheat a brushless motor😊
Now nearly 02:00 here 'Up Over' sooooo 😴😴😴😴
Cheers, Doug 😎