Electric Stunt > ESC Settings

4 cell to a 5 cell battery.

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Perry Rose:
With an FM-0c timer switching from a 4 cell to a 5 cell battery (same mAh) the rpm goes way up and needs to be turned down. Will that happen with the FM-9 Timer. I've been using a 4 cell 3300 battery getting used to the FM-9 and I want to switch to the 5 cell 3300 battery.

Mark wood:
The answer is yes. Basically the timer outputs a servo position signal and the position is in essence a ratio demand of the supplying battery voltage at the ESC. Without changing also the motor the voltage output will need to be reduced from the new battery to the old battery voltage value, ie turn down the timer output. Think of it like this, the timer puts out a signal that goes from 0-100% of the Vin or for a 14.8V 4s battery 75% would be 11.1V and for a 18.5V 5s battery 75% would be 13.9V. So, without changing the motor to maintain the same speed the timer output has to be reset to 11.1V/18.5V = 59.5 %, "turned down to 59.5%". In other words the pot on the FM0c would have to be turned down from roughly 3/4 to just under 5/8 turn thereabouts.

Ken Culbertson:

--- Quote from: Perry Rose on February 11, 2022, 02:33:37 PM ---With an FM-0c timer switching from a 4 cell to a 5 cell battery (same mAh) the rpm goes way up and needs to be turned down. Will that happen with the FM-9 Timer. I've been using a 4 cell 3300 battery getting used to the FM-9 and I want to switch to the 5 cell 3300 battery.

--- End quote ---
It did not on mine.  I flew a 5 cell 2200 back to back with a 4 cell 2800 at a contest and did not notice any difference.  What I did learn was to bring more batteries to a contest.

Ken

I just read Mark's post so I need to add that my ESC autodetects the cell count and makes that adjustment.

Mark wood:

--- Quote from: Ken Culbertson on February 11, 2022, 03:01:14 PM ---It did not on mine.  I flew a 5 cell 2200 back to back with a 4 cell 2800 at a contest and did not notice any difference.  What I did learn was to bring more batteries to a contest.

Ken

I just read Mark's post so I need to add that my ESC autodetects the cell count and makes that adjustment.

--- End quote ---

I mostly run the elcheapo ESC's and the FM0c. I find them both to be very adequate for most installations although I do run a Jetti Pro and Fiorroti in my PA models. My new timer project is being bench tested using the ZTC Beatless ESC. Provided the response of the timer and elcheapo work together, that is my future direction. Flight testing is going to begin in the near future.

Tim Wescott:
If you use the same ESC, yes.

The FM-9 is designed to be used with an ESC that has a speed governor in it ("helicopter mode").  With the governor, the ESC will hold the speed if you change from 3 to 4 cells.  Without the governor, you'll see the same thing as you did with your FM-3c.

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