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Agree all the way Alistair.Have three leccys and use Lipos because of the weight saving and power they can supply.There is a special bag that my friend purchased in America he uses for charging/discharging his ones.Would strongly reccomend you try the Lipos Alistair.They hold the charge forever,and are constantly being upgraded to better cells.Only thing I found was getting me head around them(and I'm no expert either...just having fun...safely)The only problem I have come across was one lad who used a motor that drew more than his packs C rating could provide, and fried the esc and pack.Hope this helps.Oh and I mainly fly ic models and LUV the hobby.
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Crossed wires here...Johnnie just a quick one on the reverse theory...do me a favour and charge your lipo at its C rating with your phone set to speed dial 999.You need to have another read and stop taking your quotes out of context.The 5000Mah 5amps is a cracker so I'll explain...Listen now.. 5000Mah IS 5amps.(if you like we could start up a petition to put "h" on the end of the 5amps one....)
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look,when you said "simplistically in reverse" I was afraid you might think that you could charge your Lipo at the C rating so I thought it best to say that it is dangerous to do so."As to charging Lipos. Nobody mention charging Lipos at the C rating. Only you."You left out the "not" between "mention" and "charging".Gonna say it again just in case it is true 5000Mah is 5amps,have to say this also 1000Mah is 1amp,and 10000Mah is 10 amps,and 24000Mah is 2.4 amps,and....5amps is made up of 5000miliamps....Oh and 1amp contains 1000 miliamps... and...Oh no I left out the per hour if....have a nice day and give yourself a hug
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Brilliant,an hour to use a known number of milliamps or the same known number of milliamps used in an hour....sorry,you win,after many years I am now totally convinced that there is not 1000milliamps in 1amp.We're talking about lipos here and the fact is that the C rating (rating being a very important word here)is the max,in general terms, that the pack can supply. You use this figure when choosing a setup for your modeli.e.motor,prop size,esc,etc.what's the problem here,you asked and were advised because this thread is posted in the beginners forum.In other forums people would have heated arguments over different setups,different opinions etc. and this is healthy.Keeps us thinking.You're attitude went odd somewhere along the line Johnnie.Take it like a man and say Sorry.I've had to once or twice..no probs.
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Aslan
And here was me thinking that peace had broken out.
Nobody said anything about there not being 1000 milliamps in 1 amp. The point you were arguing was that 1000 Mah was the same as 1 Amp and that is clearly wrong.
Again you have got it wrong.
The C rating is not the max a lipo can supply. The max amps a lipo can supply can be calculated from the C rating. See formulae posted earlier in the thread. Semantics I know but true all the same.

Just because this is in the beginners section doesnt mean that we are not eminently qualified to have a heated argument about something. I can assure you that my qualification to argue on this one will stack up against the best.

I have nothing to say sorry about. I am not surprised you have had to say sorry several times.

The fact of the matter is if wrong or misleading information is posted on the forum I will make every attempt to correct it. - regardles of what rear guard action is being fought to try and argue that the original information is correct.
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Please don't get personal here my friend.Your attitude is wrong."I am not surprised you have had to say sorry several times" You have every right to have a heated discussion,but to rubbish that advice is wrong.Surely you have realized by now that we are not professional electronics engineers.I'm talking lay mans term here.Leccy flyers terms i.e. the lipo says 20C, me pack has a capacity of 1000Mah so it can deliver 20,000Mah or 20amps (per hour if you like)so I think I'll use this motor,with this esc,it's an 11.1 volt pack,so I'll fiddle with different props,see how many watts the motor is pulling and...give up.Have another look at Alistairs earlier post.What's Semantics by the way?(seriously)
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Aslan
You are absolutely correct. I should not have got personal and I appologise for that.
However laymans terms are not an excuse for getting the terms wrong. For example would you say that watts are volts. Since Watts are volts amps we have only just dropped the amps from the term. I dont think you would so why drop the h from Mah. It is crucial to its meaning as a capacity not a current and crucial to the understanding of what the term means.
At the risk of continueing this discussion ad infinitum a 20C 1000Mah battery has a capacity of 1000Mah. It does not mean that the battery has a capacity of 20,000 Mah. The 20C means that the 1000Mah battery is rated for a maximum current of 20Amps. This battery as described above with a capacity of 1000 Mah could not deliver 20Amps per hour. It could deliver 20 Amps for 3 minutes (theoretically). It could deliver 1 amps for 1 hour or 2 amp for 1/2 hour or 1/2 amp for 2 hour etc etc. These are the theoretical limits.
I also think that confusion has reigned in this thread because of the use of the special case of a 1000 Mah battery as an example. It is not simple terms to use a 1000 Mah battery as an example it is a special case. It is the special case where the C rating of the battery coincides with the max amp capability of a battery.
To clarify again and I think we agree
a 20C 500 Mah battery has a max current rating of 10Amps. A 20C 2000Mah battery has a max current rating of 40 Amps. It is only the special case of a 1000Mah battery where 20C translates into 20Amps max current rating.

By the way semantics means "The meaning or the interpretation of a word, sentence, or other language form."


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No Johnnie I didn't drop the h from Ma,all I was saying is this,1000Mah is the same as 1amp,the h is dropped from the amp and in other words the batteries capacity is 1amp per hour and a lipos max supply is always,the ones I've come across anyway,calculated in amps.I'm sorry too for the wind up...now giz a hug and no hairy arm touchin' hairy arm(I hate that)Oh well of to local for a few.Cheers.
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Agree with Timbo,parts did get heated,(but it would be boring if it didn't)I fly IC first choice,but electric flight is brilliant too, and has its place like everything else.Lipos keep getting better all the time as are motors.People have different ways of explaining things(especially on paper)Certainly keeps the blood pressure(volts) up, but it does give you the power(watts) and flow (Mah/amps) to carry on:):):)Try them Phil,you won't regret it.
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i was just pulling your chains guys, i have been following your exploits , i do have an ultrafy outrage with a brushless/lipo set up, and a trex heli,
i read somewhere in one of the mags somewhere, either RCM&E or FLYER not to take too much notice of the C rating as it is only a manufacturers hype to max possible output, i was the first to answer the thread, i said then my knowledge was limited, it aint a lot less limited now, i always ask "Electric Ken" at the flying field whats the best to go with what, but im learning
group hug guys phil
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Aistair
Yes we eventually worked out I think.


Phil
You are probably right. I am sure the manufacturers will quote the max C rating they consider for their batteries and I am also sure that they could support it with scientific measurement. It is a somewhat British trait that we assume that if someone is trying to sell us something they are going to cheat us. There is advice earlier in the thread to only run the batteries at 1/2 the C rating. I dont know if this is good advice or not. I am sure that there are members of this forum that have had trouble which may appear to come from running their batteries at the max C rating. However, what is the cause. Is it that they should not run a battery like that, is it that it was a bad battery, is it that the calculations where wrong and they were pulling more than the max amps, were the batteries involved in a rough landing. Before everybody jumps on my case - I am not suggesting anything just trying to understand if the assertion that you shouldnt run them at max amps is based on fact or fiction.

If anything has come out of this thread it is for me the importance of units. Some may choose to interchange units at will regardless of their meaning. This is fine if it works for them. If they can be understood by their friends, local club, local model shop etc etc. However, if they want to be universally understood then they need to use the correct units. If anybody has any doubts about that they may want to try this little experiment. It could turn out to be somewhat expensive though.
Phone up a battery supplier and ask them to send you a battery that will give you 20 amps. If 3 mins duration is fine they could send you a 20C 1000Mah battery. Phone the same supplier and ask them to send you a battery that will give you 20,000Mah (or 20Ah). You may well end up with 20 of the 1000Mah batteries.
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Johnnie

I have never seen a published test that was designed to find out whether lipos from different manufacturers lived up to their C-ratings.

There is a lot of hearsay around that "certain cheaper brands" of LIPO are not able to deliver their C-rating. In the last issue of RCM&E, Nigel Hawes alludes to this in his article on ducted fans.

BUT HE DOESN'T SAY WHICH ONES!!!

This is one of the reasons why I, personally am still wary of buying lipos.

The assertion that you shouldn't run lipos at max amps is (I think) partly based on this hearsay, partly based on good practice. I have read in RCM&E that lipos lose their capacity more rapidly if they are used at, or near to, their max C-rating. It seems logical that if you run something flat out all the time, it's going to wear out, or in this case lose capacity, faster. I do not remember any precise figures being given to show the optimum % of C-rating to run a lipo at (which would have been useful).

Being expensive and potentially hazardous, people tend to treat their lipos with respect/care, or get their fingers burnt (literally and figuratively).

Extracting 1 extra amp from your lipo pack may give you one really good flight, but could end up costing you a dead battery.

Also - if a lipo gives up in mid air, with a BEC setup (i.e. no separate RX battery), all control is lost, so you risk losing an airframe/servos/rx etc as well as a battery, so people tend to err on the safe side.

I wish I could direct you to an authoritative source of info on how different brands of lipo perform under different conditions/loads, but there isn't one. I don't know enough about lipos to be able to tell you if operating at 1/2 the C-rating is overcautious or flirting with disaster, and I suspect it depends on the brand of Lipo.


AlistairT

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As it was me who suggested that the packs should not be used at full C rating let me elaborate. Almost any reputable LiPo manufacturer / supplier / assembler will recommend certain practices with LiPo packs /cells. For Instance...a cell should NOT be allowed to drop below 3V (off load )therefore a 3s pack for instance should not drop below 9V. Now some brands state that a minimum of 2.9, or even 2.8V per cell is acceptable,but still advise that 3V is the best "option". They are not saying you must NOT allow them to drop to 2.8V, but recommending that you dont because it is a known fact that by allowing them to deep discharge to a figure lower than 3V each cell, WILL shorten their overall life, and if allowed to drop even lower than 2.8V they will likely be destroyed.Now several years ago I did actually allow a low capacity LiPo pack to fall to the equivalent of 2.4V per cell ( accidentally in my early days of Lithium cell useage ) but through a process of very slow trickle charging, managed to get them to recover to the normal 4.2V fully charged figure. I continued to use the pack, but found that it just would not supply its usual "punch".
The same guidelines apply to discharge rates. I never said that a pack COULD not supply its stated max C rate, just that it SHOULD not. Why ?? because of what I stated about life expectancy. The manufacturer will ( reputable ones anyway.... )"admit" that using a pack at its maximum stated C rate will shorten its life, and the amount of chrge /dschge cycles that you can expect will suffer considerably if you use it at max C. Some even state that if used as such, it would be likely that only around 25 cycles would be expected. Thats right 25 !! I have been using LiPo packs for over 4 years now, and have tried just about all of the brands that were available up until approx 12months ago, when I made the decision BASED UPON USE AND EXPERIENCE that MOST cheap packs were naff. You get what you pay for, with one or 2 exceptions, and the cheap ones may not only never even produce the C rate claimed, but will almost certainly show a BIG voltage drop when pushed at max current, and will probably be useless within 4 or 5 flights.
Operating at around 50% of the claimed C rate is common good practice amongst experienced electric flight people, it may well be overcautious, but is definately NOT "flirting with disaster" !! Pushing cheap packs to discharge at very high current IS though.
Again...just my 0.02P worth - but of course ...it is correct as well :)
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Thanks Timbo

the thought that a lipo pack would go unserviceable after four or five flights is thought provoking to say the least.

How good are lipos at holding charge over time? If left unused for weeks/months do they "go off"?

Someone at my club though his packs had gone duff due to being left unused for too long.

As I'm not able to go flying every weekend, this is something that concerns me.

AlistairT
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Oh now I know what you were saying Johnnie,complete misunderstanding here,my thoughts were completely based on C rating.By that I mean a C rating of 20 amps is the same as a C rating of 20,000 milliamps.Which is why the "h" was not important....No? or am I still ranting?
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'tis a tangled web we weave...

I think that's the one Aslan

When I told my dad that the brushless motor setup (Axi 2820/10) in my tucano was drawing 40 amps he was incredulous; "don't you mean milliamps?"...

What I should then have said was;

"yes, lots of 'em"

Instead I put a battery pack in, and got him to hold the plane while I gave it the berries for a couple of seconds....

:o)

AlistairT


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