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Li-po's


Mouldy
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I Agree whole heartedly and whats more Ill tell you why!

My father has been badgering me no end to get back into flying. So around 5 weeks back we walked into Hobby Stores in Southampton. walked out with a Rainbow, an Axi 26020/8 and ESC and two 3S 2100 16C packs, (Impulse, which Im pretty sure is Ripmax).

Anyway weve flown it and off the back of that I bought the Ketana.

However! As the Ketana isnt yet ready to try the meter, I tried it on the Rainbow and guess what? The whole setup is wrong! Motor is pulling 46A WOT. The ESC is only rated at 35A and  if Ive learnt anything at all,(!), the battery is rated at 33.6A discharge.

So I have another X70 Sbec pro on the way along with a selection of props to unload the motor to try and relieve the batteries

Now am I a good student or what?  

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Ah grasshopper.....you have learned well the mysteries of elecktrickery

Here is lesson 2.

You have probably got away with not burning out the ESC because of 2 things. 

a) Most ( but certainly not all ) ESCs can stand short bursts of high current above their  rated specs.

b) The motor unloads quite a lot in the air, and this will see a consequential drop in current drawn by anything up to 25%.

 I just hope that the batteries have not been strained too far, and here is lesson 3.

Despite a fairly heated argument in another thread some time ago about the merits or otherwise of pushing packs to their limit, ( and yours exceeded them by over 30% static ) I assure you that their life WILL be shortened if you choose to run at or very close too the maximum C rate. FWIW, I personally use packs with a C rating such, that at W.O.T static, the setup pulls around 50% C. So in other words, if I get say 30A at WOT static, I choose a pack with around 60A capability, probably something like a 2200m/a ( popular capacity )  25C would do me, ( 55A max ) .

Finally grasshopper.....beware the man who says his packs are capable of HUGE C ratings, because Confucius he say..... man who flys at 60C stays up for only one minute!

Well done grasshopper....now go and have a rest with a cup of coffee and a nice sticky bun

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RCM & E Magazine - Winter 2007 issue

Nigel Hawes seems to be a little confused in respect to the chemistry of Li-Po's.

On Page 45 of the abovesaid issue, in the article "Hard Cell" he states the chemistry as being "Lithium Cobalt Peroxide", yet on Page 69 of the same issue, in the article "Electric success!" he states the chemistry as being "Lithium Cobalt Dioxide".

It appears the only thing inherently unstable here, is Nigel description of Li-Po chemistry.

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