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View Full Version : How many Lipo cells does the ESC see?


Andy m
08-24-2005, 09:10 PM
It might seem a silly question to some, but when looking at the cell count that an ESC can handle do you count all the cells?

For example with a 3s2p does it see all six cells, or just 3? I am looking at getting a high amp brushless ESC and want to be sure it can handle the right number of cells.

flypaper 2
08-24-2005, 09:29 PM
Not being to much up on electronics but the way I see it is the ESC is only concerned with how many amps the motor is drawing. For instance for a 30 amp controller you want to make sure the motor doesn't draw more than that. It doesn't care if it's a 40,000ma batt. Might just have trouble getting it off the ground.:D

Andy m
08-24-2005, 09:41 PM
It's not the amp capability I am concerned about, it's the number of cells the controller can handle. With most controllers there is a cell limit ie 8,10,12 etc, with normal nicad cells that is quite simple but with series/parallel combinations I am not too sure what the right cell count is.

Mike Parsons
08-24-2005, 09:43 PM
Andy,
Actually it is a great question :). Each ESC has a voltage rating and that correlates with the number of cells providing voltage. So you would only be concerned with the cells in series or the 3 cells as in your example of a 3S2P.

rcers
08-24-2005, 09:51 PM
What Mike says - your controller just sees the total voltage of the pack, in this case 12.6v (fully charged). It does not care about or see the parallel cells.

Mike

Andy m
08-24-2005, 11:09 PM
Thanks for the info guys, just what I needed to know. I was thinking along those lines myself but just wanted to know for sure. :)

Blob_master
08-24-2005, 11:32 PM
When selecting an ESC it is dependent on the battery voltage supplied to it and the maximum current the motor will draw. E.g. a 3s2p battery pack consists of 3 cells in series, in parallel with another 3 cells, hence if the cells are 4.2 volts each and 1000mAh capacity you finish up with a 12.6 volt pack with 2000mAh capacity. If youíre motor draws 20 Amps maximum, you would therefore need a 3 cell (12.6v) 20 amp ESC.

Note: Remember that the cells also have a maximum discharge value, so in the above example your batteries would need to be capable of 10C discharge (2000mAh x 10).

Hope this has helped.

Lazyflier
08-26-2005, 08:27 AM
Just remember the ESC cut off voltage is set from what it first reads from the battery. If you install a 3 cell pack that is not fully charged the ESC may read the pack as a 2 cell and automtically set the LVC (low voltage cutoff) to 6v instead of 9v. If you run the battery to LVC while flying you will run a good chance of ruining your battery due to going past its safe discharge voltage. For that reason I use ESCs that let me program the LVC.