## Sunday, January 27, 2013

### Calculations For Additional Capacitors Necessary in a certain 21-motor Airplane Setup

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These are my calcs, in regards to Posts 540~543 (here: http://www.rcgroups.com/forums/showthread.php?t=952523&page=36 and here http://www.rcgroups.com/forums/showthread.php?t=952523&page=37).  Basically, I tried to figure out how many additional capacitors are necessary on each of the 21 ESCs in order to offset the voltage ripples caused by increased battery lead length (which can destroy/damage the existing capacitors in your ESC if you don't add capacitors to help absorb the magnetically-induced voltage spikes [refer to post 1 in the above thread for more info about this]).

I am only putting this spreadsheet here because RCGroups won't allow it as an attachment on their website.
The above link is to the old spreadsheet.  I have corrected some errors, and the NEW SPREADSHEET LINK IS FARTHER BELOW!

Update: 20 March 2013 - Spreadsheet corrected and now available here (go to File --> Download to save):  https://docs.google.com/file/d/0BwHItOaHOOvdQmp3c3gydzV3SU0/edit

Update notes:  I added the "Total Capacitance Needed" (Row 25 in the new spreadsheet) in the calculations, and I removed the row called "Additional Length, beyond ESC's design, for which you must add Caps (in.)" (Row 22 in the old spreadsheet).  I then added Row 26 as well, and corrected the formulas in Row 27.  This allowed me to account for the additional current in the entire wire station length, not just in the length beyond that of what the ESC was intended to handle (Cell Q14) at its max rated continuous current (Cell Q11).

Here is a table of the differences in end-results between the old and new spreadsheets, for this one particular example:

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For jaccies (referring to Post #579 here)

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