Heli balance changing as lipos discharge ?

[pk-surfing]

Hi,

I've picked up on a strange situation with the balance of my Trex 450 Sport that has me scratching my head.

I noticed that I can get it balanced perfectly for CofG using a fully charged 2200mah 3S lipo but when the lipo is discharged to 20% the CofG moves back by 5mm, the lipo is lighter when it is discharged !

I couldn't believe it at first but I checked it out using my digital scales (measure down to 0.1g) that I use for balancing my heli rotor blades.

All my 2200mah 3S lipos change weight by about 13 grams from fully charged to discharged down to around 20%, I have tried this on 8 lipos and they are all lighter when discharged and heavier when charged.

Has anyone else come across this or is it something that happens but nobody has picked up on before ?


Paul

[Voodoo]

This is what Einstein has meant with:

[cjcj1949]

It's probably something to do with the time of the month. Should be ok tomorrow. You might find the lipos a bit tempremental today. Try and be patient.

Chris

[mgjackson]

That figures....An electron has mass, although not very much 9.1x10**-31, but a lot of them get used up . A coulomb is the number of electrons which rush past a certain point per second - about 6.2415 * 10**19.

So for a 5 minute flight, thats 300 x (6.2415x10**19) x (9.10x10**-31) x 25 (C charge of a typical LipO) which is give or take a bit, 13 grams.

[barney]

Did you not realise as the lipo gets warm it gets lighter too so affecting the C&G

[barney]

Used Lipos are lighter

DANGER Do not do attempt to this at home as it can seriously damage your wallet DANGER

Take the test

Take one new lipo and drop into a bucket of water and it sinks. Take one old puffed example and it 'FLOATS'..so it must be lighter

[pgkevet]

E=MC^2
These units are Joules, Kilogrammes and lightspeed at 300,000,000meters/sec

5 mins flight on a 450 uses (say) 2000mA @ 12V = 24WAtts = 2Watthours
Which = 7200Joules

7200/C^2=mass change in Kilos = 7200/one heck of a lot so the mass change is too tiny to bother with !!!

Electrons will flow from one pole to the other in the batery..they aren't 'lost' they just lose their potential energy. Exactly the same as the mass of a boulder on the top of a mountain is much the same (but not quite...different gravity well) as the mass of the same boulder at the bottom of the mountain after it's crushed several hotels.


However if the lipo falls out of the heli in flight the heli actually gains mass and gravitational attraction and pulls the panet up to itself

[adieuk]

i love april

[Steve]

One of the most mis-quoted formulas ever!

E does not equal MC squared.

E is proportional to MC squared.

[moyesboy]

If E is proportional to mc^2, then E=mc^2 if you use the right units for m and c?