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Question About 12S & 14S

Old 10-19-2020, 07:40 PM
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Suprawill1
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Default Question About 12S & 14S

Hi All,
Is it ok to run a 12S EDF/ESC system on 14S if I keep the current, wattage and heat in spec?
What I plan to do is run the 12S system with 14S lipos on a watt/amp meter and raise the throttle till I reach just under the maximum allowance of the 12S system and then program my transmitter to not exceed that percentage at full throttle. Does that sound safe?

Just to let you know why I'm doing this, I'm going to upgrade the 12S jet to a 14S system soon after purchase so I didn't want to expense both 12S and 14S batteries.
Thanks for your thoughts.

Will
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Old 10-19-2020, 10:41 PM
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quorneng
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As long as the ESC is rated to handle 14s you should be ok. Throttling a motor from a higher voltage may reduce its efficiency a touch and thus increase its heat generation for the same power level.
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Old 10-20-2020, 12:10 AM
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ron_van_sommeren
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Originally Posted by Suprawill1 View Post
... Is it ok to run a 12S EDF/ESC system on 14S ...
Current and power drawn are proportional to voltage squared respectively voltage cubed.
Going from 12s to 14s, current drawn wants to increase by factor (14/12)≤= 1.3, 30% extra.
Power drawn wants to increase by factor 1.5, 50% extra.
Increase in current with one or two cells added simple table - RCG
(In full: proportional to pitch, #blades, voltage≤ respectively voltage≥, Kv≥ and diameter⁴, small changes, huge increase).
Ignoring bit of extra voltage losses in battery, wiring, controller and motor due to higher current.


Originally Posted by Suprawill1 View Post
.... What I plan to do is run the 12S system with 14S lipos on a watt/amp meter and raise the throttle till I reach just under the maximum allowance of the 12S system and then program my transmitter to not exceed that percentage at full throttle. ...
If current at wide open throttle is too high for the controller then reducing throttle to get current below ESC max.current is not a good idea. It is even harder on ESC than to keep overamping at full throttle. Better to prop down a bit to reduce current.
See:

Last edited by ron_van_sommeren; 11-25-2020 at 08:49 PM.
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Old 10-20-2020, 12:35 AM
  #4  
Suprawill1
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Originally Posted by quorneng View Post
As long as the ESC is rated to handle 14s you should be ok. Throttling a motor from a higher voltage may reduce its efficiency a touch and thus increase its heat generation for the same power level.
Ok, thanks. Fortunately, it should be a short term solution until I upgrade the EDF. I will also upgrade the ESC from the start to handle the 14S.
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Old 10-20-2020, 12:40 AM
  #5  
Suprawill1
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Originally Posted by ron_van_sommeren View Post
Current and power drawn are proportional to voltage squared respectively cubed.
Going from 12s to 14s, current drawn wants to increase by factor (14/12)≤= 1.3, 3% extra.
Power drawn wants to increase by factor 1.5, 50% extra.
Increase in current with one or two cells added simple table - RCG
(In full: proportional to pitch, #blades, voltage≤ respectively voltage≥, Kv≥ and diameter⁴, small changes, huge increase).
Ignoring bit of extra voltage losses in battery, wiring, controller and motor due to higher current.



If current at wide open throttle is too high for the controller then reducing throttle to get current below ESC max.current is not a good idea. It is even harder on ESC than to keep overamping at full throttle. Better to prop down a bit to reduce current.
See:
Oooookay. That's a mouthful!
As mentioned in the above post, I will upgrade the ESC from the start to handle the 14S. The EDF will have to endure a bit until I get the upgrade that the 14S is intended for.
Just didn't want to have to buy 12S lipos for the short term. Thanks for the hit and the links!
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