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Alistair, one of the considerable advantages of the LiPo over the nickel based batteries, is their ability to hold a charge almost indefinately. Once peaked to 12.6V ( optimal voltage for a 3s ) a pack will hold good for AGES...weeks, nay months.... and is one of the reasons I use them. I have amongst my fleet a small "superfly" wing which lives in my car boot fully charged and ready to go at a minutes notice, or indeed whenever I pass a likely looking field / mountain-side whilst out and about...of which there are zillions where I live.... 15 mins from Snowdonia :-)
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This sounds good - going through the rigmarole of topping up batteries if a flying session is rained off is a pain.

Mountains? Now I'm jealous

I live in East Anglia, where mountains are but a distant dream.

Airfields on the other hand - loads of 'em, and as a result - plenty of air traffic to avoid. Not usually the low-flying jet-propelled sort with 30mm cannon you get round some welsh valleys though ;o)


AlistairT
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Oh yes....not only do I get an almost daily display from the RAF valley hawks, but a chap I know ( not very well unfortunately, although I have been priveledged to sit in it on the grass strip runway ) keeps amongst his other aircraft a Spitfire hangered about 12 miles away from my house, and we often enjoy a free short display over the bay at the end of our back garden. He takes it to shows fairly regularly in the summer months, and has to pass our place for nearly every one. Also whenever he has had to do maintennace, a quick trip to a safe testing place puts him again....right at the back of our house over the bay :)
Wifey and I are often seen running into the back garden following the sound of that loverly big merlin engine a short distance away.
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I'm starting to see a trend here.

My wife was incredulous when the house we'd put a deposit down on turned out to be;

- 400 Yards from a model shop
- next to the airfield where the local model club flies (Royston and District MAC - flying on Bassingbourn airfield)
- about 15 minutes drive from the Gransden airfields, Duxford and Shuttleworth

Unfortunately you don't see many current RAF types, but I work in Peterborough which is used as a live firing range...sorry, wishful thinking...which is NEAR a live firing range for the harriers from thereabouts.

Still no hills though.

the wifey has developed a fondness for planes, in particular the vulcan. I don't think she's ever seen so much wing in one place.

AliT :)
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Timbo
Who do you consider to be reputable manufacturers of lipo's and where do they publish the information on their usage. Which manufacturer claims that their battery will only last for 25 cycles if ran at max current.

Alsan
To be strictly correct the units of the C rating is reciprocal hours (or per hour if you like). In order to get the max amps you need to multiply the c rating by the battery capacity. That then cancels out the hours part of the equation. However, that being said even battery manufacturer state that the C rating is xxxx amps so it is not surprising that confusion reigns
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Johnnie. Which manufacturer/assembler(s)of LiPos I consider to be reputable is not really the sort of answer I feel happy to divulge on public forum -I would not wish to be seen to be favouring one over another, for fear of being accused of trade connections or whatever. Most aforementioned reputable companies publish performance figures for their products, but as far as I know NONE claim that their packs will "only last for 25cycles if ran at maximum current". It was my suggestion that this was the case, and this is based on written statement of fact, from one of the world leaders and PIONEERING COMPANIES IN THE FIELD OF MODEL AIRPLANE LiPo packs
KOKAM - FMA - Fred Marks himself, who has stated - and I quote " Experience has shown that the determinant of cell life and performance is the temperature the cells reach during discharge. A cell run continuously at the maximum C rate will lose capacity to 80% in as little as 25 cycles. Properly managed, the same cells run with bursts of < 10 sec and average current of half the maximum allowable discharge rate can last 500 cycles."
Now, a pack / cell that achieves only 80% of its original capacity IS IN MY OPINION "cooked /naff / jiggered / or whatever you want to call it".
If you would like further reading and data to support the cautionary advice I have given so far, please see the following link.http://www.fmadirect.com/lipo_handbook/FMA_Lipo_Handbook_Section2.htm
I do detect a certain inclination within your posts towards confrontation. Please remember that this thread was posted in the "beginners" section, and being over pedantic in response to other peoples replies ( not mine incidentaly )who have not yet achieved the level of experience or knowledge that perhaps you or others have, is not IMHO helpful, or friendly.
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Timbo
Sorry you feel threatened by being asked to support your opinion with fact. Does anybody else on the forum have any factual information that can support Timbo's assertion or is it all hearsay.
And if you feel this is confrontational I am sorry. However from you own reference I quote
"2. What should not distinguish one cell from another

• Old - wives tales

• Unsubstantiated vendor claims; if data isn’t available, it may not be good or he may not have it

• Anonymous claims and critiques from someone you do not know

and I guess you fit in to the last category.

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Yes and I guess the thread is over for me as well.
If you are prepared to accept and take what people say at face value then on your own head.
You might want to review the reference made by Timbo.
As a scientist I understand it. And it does not necesarily support Timbos opinions.
Its easy to make statements. It becomes a lot harder when you have to back up those statements with facts and figures that would stand up to scrutiny.
Guess the battery manufacturer are rubbing their hands with glee as they see people overspecifying their requirements.
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Of course it suppoorts my theory. What I simply said was that constantly discharging a LiPo pack at its maximum C rate will shorten its life. FACT. - read the blinking link man, and stop being so bloomin self righteous. For someone who's first post in this thread admitted they did not even understand 2s / 3s etc you are pretty bold with your condemnation of experienced electric flyers.
Oh, and I dont feel threatened thank you.
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Johhnie
Sorry you jumped out of the thread. Come back. You were working hard at finding your way through some pretty badly presented and sometimes even downright wrong information. Some should be thanking you for helping them understand some of the very basics.
A lot of the posts were waving in the wind - desperately trying to change their first answers to match your corrections.
I think if you hadnt posted in the beginners section you would not have come up against the closed RC modellers club syndrome. i.e. they all think you are a beginner and they all think they know it all. It was pretty obvious from the beginning that you understand electrical theory.
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theory into practice,,
as i have mentioned earlier in the thread, i have a plane, a floaty foamy bipe,,
i also have a trex heli,
now then, i keep to the same lipos in both craft, the plane lipo which is very rarely flown at full chat for fear of pulling the wings off will still charge to 95% of its claimed capacity, the heli lipo is a different story, with the throttle set for optimum head speed, it is now down to around 85% of its capacity and this is the second lipo pack as the frst one lost its bottle, to my mind this supports timbos case that the more you hammer it the faster it breaks, "its lojical jim" (see guys im taking it all in and learning).
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Thanks Phil, but I must stress that it is not just "my case". It is a well known FACT that cooking your LiPos at absolute maximum discharge capability WILL shorten their life, and I think the link that I supplied confirms this "theory". If the pack is not provided with some form of cooling either then matters will get progressively worse. If anyone wants absolute proof,and they have money to burn, then I suggest they buy a pack, charge it at 1C, then dischrge it at a steady full C about a dozen times,recharging at 1C between use, then check the voltage reading under load. Also see how many m/a you can put back in.
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Further to the website suggested by Timbo, the advice on the following website seems well informed, and includes info on how quickly Lipos lose their charge over time while in storage (NB charge, not capacity).

http://www.flyingsites.co.uk/features/lipo.htm

and there's this one

http://www.rchobbies.org/lithium_battery_breakthrough.htm

and this one

http://www.flightpower.co.uk/

and these ones

http://www.cheapbatterypacks.com/main.asp?pgid=howto&sid=771584

http://forums.all-battery.com/index.php?showtopic=1281

http://www.extremerc.com.au/Extreme_Power.htm

I'm off to cook my CP1700s at 2C in preparation for some 20C action at the weekend.


AlistairT
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