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Switching from 3S lipo to 4S on same motor

Spikee

Junior Member
#1
Hello!

I have a super sexy Multiplex twinstar 2 which has the following setup:
Torcster Brushless Gold A2826/10-1400Kv
(same as the turnigy one)
Graupner cam slim 17x7.5 cm (6.6"x3") prop
and
Torcster Speedcontroller ECO BEC 20A V2

According to measurements made by natterer-modelbau my engine uses 9.26A @3S lipo:

Screenshot 2013-11-13 01.44.25.png

I got a nice deal on a 4s 5000mA lipo and it would be nice if i could power my plane from this.
Most of the time i cruise at 10-20 % of the stick speed and it handles nice. I just want it to get a better climbing rate and an improved top speed.

According to the prop chart i still have some nice Amps left on the prop that I'm using. So a 4s lipo shouldn't be a problem. The max voltage of my motor is rated as 11.1V but this is nominal so i probably have some head room.

Would this work in reality or will it damage my motors/esc's ?
(I do a lot at cruising speed , only little fast altitude changes or high speed).

I would like to receive your input,

Spikee
 
#2
Ready for the long answer?......NO, just no.....don't worry, working on first draft of why this is would not make for a fun day at the park
Will get back shortly lol
 

pgerts

Old age member
Mentor
#3
Spikee = Coward? ;-)
You wont get a lot more top speed from a twinstar due to its wing profile. It requires a LOT of power to get high speeds.
The amps will probably increase in Square of the voltage increase (better to measure the amps) and the motor does not say anything of running on 4 cells but i have never failed when tried.
If you want speed - put the motor and 4 cell into a small funfighter.
 
#4
Thanks pgerts! I have a bad tendency to analyze the micro, truncate questions down to a simple yes or no. You on the other hand are good at looking at the whole picture and asking "why?"

Truth of the matter, yes your motor will run on 4s with some down propping to account to amps. Motor efficiency will decline notably, heat may get excessive and windings inside motor will fail far quicker than in a suggested 3s application. Pgerts is suggesting if speed is what you need, than you have the wrong craft. Even if motors work fine for some undetermined period of time, you will be disappointed by lack of increased performance with the TwinStar.
 

rcspaceflight

creator of virtual planes
#6
This fun fact is meant for cars, I don't know if it applies to planes, but: It takes 8 times the horsepower to go twice as fast. If you want to double the top speed of a vehicle (car), you need 8 times as much horsepower. Which is why aerodynamics is so important. Decreasing the amount of vehicle (again, car) that is hitting the air, the faster it can go with the same power. I read all of this in a Hot Rod magazine article, but I'm sure the info crosses over into planes because the article was about how important aerodynamics are.