Johnnie

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.

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."

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.

sorry and not milliamp per hour

Oh and by the way adding in the "oh no I left out the per hour" confirms your misunderstanding of the the units. It is milliamp hour and milliamp per hour.

Aslan fine if you want to change the SI system of unit which is international. Maybe you should go and check them out. Ignorance is bliss I guess.

Alsan 5000 Mah IS NOT 5 Amps. It is 5Ah. No matter how many times you say it it will never be true. As to charging Lipos. Nobody mention charging Lipos at the C rating. Only you. Johnnie

Alistair I am loosing the will to live. Suggest you go back in your box. I had no problem with your information. As I said there was a lot of good replies - yours was included in that. That is until you came to the C rating. Quote The C rating purports to show how many amps a lipo cell can supply, at its limit. Unquote This is not correct. As Aslan thought at the begining people take this to mean that 10C or 25C mean 10 amps and 25 amps. I do agree though that your further posts clarified that However, somewhat pompous that you think you are giving advice voluntariy and unpaid. Wake up smell the coffee. This is a forum! Now to Aslan Get angry all you like. Suggest you go back and read your posts. 1. quote Your reverse theory sounds good but things arn't what they seem unquote The reverse theory is absolutely correct 2.Quote 5000Mah or 5 Amps Unquote This is an absolute nonsense statement. Mah stands for milliamp hours, amps off course is amps. One term is capacity the other is current. 3. Quote C rate is how many amps a Lipo can supply Unquote This is is nonsense. Agree you have retracted now by trying to show you understand it. I am sure this new found knowledge has come about because of this debate we are having. 4. quote Forget about the fractions of an hour one unquote Again nonsense. Simple algebra will show that in fact the C rating does give the fractions of an hour the battery will theoretically last at maximum rated current. Maximum current in milliamps = C rating X Capacity Time battery will last at max current = capacity / max current Answer = 1/C rating in unit of hours QED the C rating shows what fraction of an hour the battery will last at max current. On your last post you are just repeating what I said in my last post. No doubt trying to show your new found knowledge. Johnnie

Mike The fact is what I read on the internet was correct - i.e was the good advice when it came to the C rating. There is no doubt that some of the replies received were suggesting that the C rating was the max current e.g. if it was a 25C battery then the maximum current was 25 amps. This is absolute nonsense. So that advice was also absolute nonsense. There was lots of good replies and information thought on the designation of batteries etc. Johnnie

If you go onto SMC web site (http://www.sussex-model-centre.co.uk) and search for glass tape you will find what you are looking for. Johnnie

Alistair Know what you mean. However, I am convinced that the paracetamol has something to do with the fact that in 5 days i have advanced from knowing nothing about lipos to thinking that I am an expert!! Timbo You make an execellent point. It would not the way to go to run these batteries at max current ratings. However, finding out what that is makes it easy to run them at 50%. Now back to the day job Johnnie

Aslan You have lost me or we are talking at cross purposes. For example. A 25C lipo battery does not necessarily have a max current discharge rating of 25amps. If the lipo is 1000 Mah then the max current would be 25 amps. If the lipo is 500 Mah then the max current would be 12.5 amps. If the lipo is 2000 Mah then the max current would be 50 amps. In other words the C rating of the battery only coincides with the max amps if the battery is a 1000 Mah battery. Rereading the thread again and your responses I can see you have some confusion between Mah and Amps. The two units are completely different. Amps is a measure of current flow and Mah is a measure of capacity. On your post of the 30th a battery cannot have a capacity of 1000 Ma - the correct term would be a capacity of 1000 Mah. This means that the battery could theoretically supply a current of 1000 Ma for one hour or alternative 100 Ma for Ten hours and so forth. In the your same post a 5C , 5000 Mah battery would have a max current of 25Amps not 5 amps and a 10C, 10,000 Mah battery would have a max current of 100 Amps and not 10 amps. The reason why we need to know the max amps is crystal clear. Johnnie

It would be much more appropriate to say that swearing is offensive and is definitely not required to put you point over on this forum.

Thanks Alistair Clear to me now. If anybody from the magazine is reading this, this would make a great subject for an article. Johnnie

Alistair Took so long to write my reply and trying to do my day job that our messages crossed. Need some time to work it out but I think you are agreeing with the definition of C. John

Mike Not sure what is the good information you mean. i.e. the forum or the internet as they are at odds with each other. If you Google "Lipo safe discharge current" there is overwhelming agreement about the meaning of the C rating of a battery. It is not the maximum current that the battery can supply. However, the maximum current can be derived from the C value using the following. Max current = Mah capacity of battery X C rating / 1000. From one particular manufacturer you can find the following information on their batteries (and I am presuming that they know best) the figures are in order Capacity(Mah), C Rating, Max Discharge current. 450, 25, 11.3 600, 25, 15 850, 25, 21.3 1000, 25, 25 etc etc You will be able to see that this agrees with the above formulae. As Aslan says above the important figure is how much the battery can supply and from that the length of time the battery will last can be calculated from the capacity. However, the trick is to know what that amperage figure is. Johhnie

Just found another defintion of C on the internet. Current is rated in C's. C is how long it takes to discharge the battery in fractions of an hour. For instance 1 C discharges the battery in 1/1 hours or 1 hour. 2 C discharges the battery in ½ or half an hour. So I guess that is the same logic as I used above i.e. a 10C battery will discharge in 6 minutes. Based on this definition if the battery above was a 2000 Mah capacity and it was 10C the max discharge current would be 20A. Now I am really confused

Thanks for the answer Alistair. Still a bit confused about the C rating though. I thought that if I was wanting to charge a 1000 Mah battery say with a 100 ma charger then I would have to charge it for 10 hours. So simplistically in reverse then I could draw 100 ma for 10 hours or 1 amp for 1 hour etc. So in your example above for a 1000 Mah battery I would expect to draw 10 amps for 6 minutes. So where does the 10,000 Mah come in. Johnnie

Great idea John

Refreshing views at last about joining a club. I am sure that joining a club might get you flying faster but it is not the only way. Interesting point above about switching on a transmitter close to a club site. Maybe this is the reason that all over this forum there is advice to join a club. Of course 2.4 Ghz will get rid of that fear - hopefully Johnnie

Bit confused about the designation of Lipo batteries. 3S, 2S etc. What does it mean. I see some advertisements for Lipos that dont mention that designation. Johnnie

The e-mail notification is going crazy. Just received three e-mails that I had responded to this thread

Just remembered. The problem was the batteries in the controller. They were flat!! Thats the reason it didnt charge the Pico Johnnie

When mine arrived I thought I charged it. It would hardly get off the ground. When I charged it properly it worked OK. Johnnie

just noticed on the futaba site that they also now have a 7 channel and 12 channel version of 2.4gh radio. http://2.4gigahertz.com/systems/radiosystems.html