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Thread: Li- Poly


  1. #1
    Aero330LX's Avatar
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    Li- Poly

    Hi,
    I am thinking about fixing up a trainer I had, and converting it to electric. I was curious about these Li-Poly batteries, but need to get some info on them. I basically need to know everything about them, as I don't know anything at this point. i need to know what chargers can be used, how much battery I will need, what the flight times will be like, how much they cost, how they last, all that good stuff. If anybody has any info. that they would like to share it would be much appreciated. Any good websites on this topic would also be appreciated. Thanks in advance for your time.

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    BlackCloud's Avatar
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    Li- Poly

    Since this subject is relatively new on RCU. You would be better off trying under RCgroups com / Electric or ezonemag com is a good source of info on electric. Both will take you to the same area of discussion boards. You will find most of the electric gurus are one the zone. That is until word spreads about the RCU boards. Good Luck!
    Murphy\'\'\'\'s law must have been written by a pilot

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    Li- Poly

    Lithium Ploy is new to the RC hobby and has a good future for giving longer flight times with good performance. Since is it very new people are just learning how to use them safely. Because its so new there are a number of problems to be worked out from safety to charging.

    In the near term I would suggest that you start out with NIMH or Nicads which are available at low cost and have available equipment to charge safely. In a year or 2 the lithium battery area will become more main stream and safer.

    Steve

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    d_wheel's Avatar
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    Li- Poly

    Here's one place to start your education on LiPoly battery packs:

    http://www.helihobby.com/html/lithium_polymer_.html

    As far as converting an existing trainer, you might want to reconsider. Electrics are built with a different mindset than glow models. Your trainer will probably (you didn't say what it is so this is just a guess) be too heavy to be a good candidate for electric. I am by no means an expert, so others with more knowledge may want to jump in here.

    What is your experience level? Maybe someone can suggest a good model to start with if we have more information.

    Later;

    D.W.
    Getting old aint for sissies!

  5. #5

    Li-poly

    Check www.EspritModel.com web site for more information.
    We have them in stock.
    If you need help!!!!!!
    www.espritmodel.com

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    Li- Poly

    To date the specs provided have been in many cases not accurate leading people to use the lithium cells in a manner that is not suitable. In one case the cells were rated for a higher current discharge than was actually possible and still get anywhere near the rated capacity. If you are willing to play with very expensive batteries and can afford to buy more when they are damaged then enjoy--just be careful not to start too many fires!

    Steve

  7. #7

    Li-poly

    I would not be so sure.
    The Aero-Model with people from us has been testing this batteries for long period of time.
    I have personally flew my Diablo Top FG (65"x62", 8 lbs.) at John Nall meeting many times for 20 minutes. Unlimited vertical, flying time up to 25 minutes.
    Hacker B50 9XL w/5.2:1, 16X10 prop, 2x3S4P 7800mAh Li-poly batteries.
    The plane went down from 8-1/2 to 8 lbs.

    Zb/Esprit Model
    If you need help!!!!!!
    www.espritmodel.com

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    d_wheel's Avatar
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    2x3S4P 7800mAh Li-poly batteries.

    I'm new to electric and am not familiar with the motor you are using, so have a question. Are you running 2, 3S4P packs in series or parallel?

    Where can I find a motor calculator that has LiPol batteries in it's database?

    Later;

    D.W.
    Getting old aint for sissies!

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    Re: Li-poly

    Originally posted by modest-master
    I would not be so sure.
    The Aero-Model with people from us has been testing this batteries for long period of time.
    IZb/Esprit Model
    The thread is about what should be considered for a new person to electric. Asking some one to buy hundred of dollars of batteries and then to spend a similar amount of lab type power supplies to charge them is not reasonable. For people starting they are much better off using proven safe power sources IMHO.

    I have been flying Lithium powered models for some time now--my Eco 8 flew for well over over 75 minutes of an charge. We also flew a Stinger 400 with lithium ion cells for 2 hours and 8 minutes covering 91 miles. I think I have a pretty fair idea of what is possible--but that does not make it practical for most new fliers.

    Handeling and safety issues have not been addressed well enough to make the lithium option main stream.

    Steve

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    Dave Lilley's Avatar
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    Li- Poly

    I think that the application and the cells needed directly affect the cost per benefit ratio.

    For example, I am running a 2s2p 1020 LiPoly pack in a couple if my indoor planes. The cells cost about $12.50 each, for a total of $50. This is especially noteworthy considering that the LiPolys replaced a $35.00 720mAh NiMH pack. With the 2s2p 1020 pack, the pack effectively has 2040mAh capacity, and it can run for ~45 minutes or more. The 1020 pack had ~65% more run rime than 720 pack, yet only cost ~30% more. To get close to the same run time from NiMH packs, I would have had to buy three NiMH packs, for a total of $105.

    This may not be the case for higher amp applications and larger LiPoly cells, and really you would need to price out both options to see if the run-time and price fit within your goals. As for safety, according to the literature I have read, LiPoly cells seem to be safer than Li Ion cells.

    More Li Ion and Li Poly Battery info:
    http://www.semiconductor.sony-europe...er%20Focus.pdf
    http://www.panasonic.com/industrial/...df/li-poly.pdf
    http://www.panasonic.com/industrial/...ion/index.html
    http://www.virtintern.duke.edu/nokiateam/batteries.ppt
    http://www.canyonriver.com/information_battery.html

    Dave Lilley
    Dave Lilley

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    Li- Poly

    Originally posted by Dave Lilley
    As for safety, according to the literature I have read, LiPoly cells seem to be much safer than Li Ion cells.

    Dave Lilley
    Safer--maybe a bit--but there are pleanty of cases of fires from charging failures with Lipoly cells. To their credit the Lithium Ion cells at least have a PTC device built into the cell to shut it down if over heated--but it is not perfect!

    Maybe you need to shop around to get better deals on your 720NIMH cells--$5 /cell is pretty high! They should be more like $2 each.

    Steve

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    Li- Poly

    Many fires resulting from LiPoly fires seem to be related to the chargers failing to shut off at peak. The technology in both the Li Poly chargers and cells is still new, and these types of problems happened frequently with early NiCad chargers. This still happens with some mature battery technologies. Even with years of advancements, lead acid car batteries are still known to explode.

    At least LiPoly don't vent and explode like Li Ion, and at least they can be safely disposed in a standard landfill.

    That said, as with any electrical device, there is a risk, and proper safety precautions should be taken at all times.

    The published caveat for all cells and all chargers is that they should never be left alone, whether they are NiCad, NiMH, LiPoly, Li Ion, etc.

    As for the price, $35 was for a built pack, with leads, from a retailer. I just looked and found the same 720mAh pack for $25 at another retailer. Even at $25, the total for three packs would cost $75. I know that if I built my own packs, I could save money. However, I have never been good at soldering packs, and for me, the extra $5 or so is worth the money.
    Dave Lilley

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    Li- Poly

    Originally posted by Dave Lilley
    Many fires resulting from LiPoly fires seem to be related to the chargers failing to shut off at peak. The technology in both the Li Poly chargers and cells is still new, and these types of problems happened frequently with early NiCad chargers. This still happens with some mature battery technologies. Even with years of advancements, lead acid car batteries are still known to explode.

    In general the failure mode for NIMH and Nicads is much less likely to result in a lthium fueled fire that is very difficult to put out.

    Now back to the original point--which you have helped make also--lithium batteries and their chargers arte not really ready for the main stream electric fliers just yet. Safety/charging issues still are to be worked out. IMHO the hobby industry needs to set some standards for the charging equipment and batteries to avoid problems.

    Steve

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    Li- Poly

    It is a new technology, and I agree that it isn't mainstream yet, however, for folks who don't mind the learning curve (dedicated hobbyists), it is just one more technology to consider. (...with an special emphasis on safety.) Even with its limitations, it does seem to be picking up acceptance.

    As for standards, I agree that it would be nice to have them, especially with the more divergent parts of the e-flight hobby, such as motors, ESCs, batteries, etc. Standards would go a long way in moving electrics from a niche to a mainstream hobby.

    However, since Li Poly technology, as with most battery technologies, is being driven by forces other then the RC industry, and by companies on multiple continents, I think standards are very unlikely, at least for the near future.

    ...so, I agree that it isn't mainstream, but if used carefully, it offers good flight times at a decent price, at least with the small stuff.

    (feel free to disagree) I personally feel that LiPoly will have a future in RC e-flight.

    Dave
    Dave Lilley

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    Li- Poly

    Dave,

    Try looking back at what I wrote before making your comments. The thread was about a new electric flier converting a gas trainer. In my view someone new to this should start out with proven safe equipment.

    If you want to play around and are aware of the problems and dangers then fine. It is not however a good idea to encourage inexperienced new people to do the same.

    Steve

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    Aero330LX's Avatar
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    Li- Poly

    Hey Everybody,
    I think I may have started some confusion here. This is for a trainer, but not for me...it's for my Father to fly. I've been flying planes for a long time! LOL I fly IMAC myself. I was wanting to go with these Li-Poly's to learn about them myself and do it on something that wasn't so expensive, while at the same time giving my father longer flight times. NiCd's are not an option, because I will no longer use them. They are old technology, heavy, and just too much hassle to maintain. NiMh are a little better, but they just don't hold up real well over time when quick charging. I have a really expensive Robbe Infinity II Charger, and was wondering if the charger could be setup to charge the Li-Poly's. Charge Rate and Peak voltage and that kind of thing can be manually set on the Infinity. Basically this is a learning experience for me on the batteries, but I don't think I need to go back to a trainer yet. hahaha I run Li-Ion currently in my IMAC bird and am familiar with the nature of those batteries. This is basically a two-fold deal. An experiment of sorts to learn this new chemistry and trainer for my Dad that will give enough endurance for him to stay up and learn some on. I'm hoping I can get a 20 flight duration before 'run down' on the airplane. This happens to be a 25 size trainer that should weigh in the 3.5-4 pound range. It's an old MEN Trainer believe it or not. If you have been in it long enough to know what that is you are as hopelessly addicted as I am! hahaha I appreciated all the posts so far...keep them coming.

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    Li- Poly

    Originally posted by Aero330LX
    charging. I have a really expensive Robbe Infinity II Charger, and was wondering if the charger could be setup to charge the Li-Poly's. Charge Rate and Peak voltage and that kind of thing can be manually set on the Infinity.
    The answer is no--the Infinity will not function as a lithium charger. There are some that will do lithium, Nicad and NIMH but many of them are not ideal solutions for lithium due to issues with overcharging. Do some reading in the different forums regarding chargers.

    The problems you encountered with NIMH are not true for all types available. For high current applications the Sanyo HR2600 are very hard to beat. I have packs that have been used for hundreds of cycles.

    Steve

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    Dave Lilley's Avatar
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    Li- Poly

    You need a charger specially designed to charge LiPoly packs. A standard NiCad or NiMH charger WILL NOT work, and definitely lead to a fire, short, disaster...

    Some of the new chargers include the capability to charge NiCad, NiMH, and LiPoly. These include the Orbit and Schulze.
    Dave Lilley

  19. #19
    Dave Lilley's Avatar
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    Li- Poly

    I agree that the 2600 are excellent cells. If you already have an Infinity, they may give you close to the run-time you need.
    Dave Lilley

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    Li- Poly

    heres an excellent page explainming all the basics

    http://www.flyelectric.ukgateway.net/lithium.htm
    common sense is the least common sense of all

    come and fly capiche with me!

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    Li- Poly

    Another good source of info is Park Flyer Motors.

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    Li- Poly

    I'd talk to Dave at radicalrc.com. He has a deep knowledge of all types of batteries, including li-poly. His on the shelf stock and pricing is good.

    Jon

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    Li- Poly

    have you already picked out a specific trainer? what size , model, etc. this will help with sizing the motor/battery/prop combo.

    Some lipos (etecs, kokams,) can be ordered from Radical RC. These batteries are better suited for smaller applications, say 15 - 25 size. This is based on how many amps the battery can put out in one specific time, which would be about 10 amps on the 3 Series packs. He also has the best charger, the orbit. make sure to get v6.2 or later release.

    Regarding bigger lipos, Thunder power packs can be bought from Esprit Models. Per cell, the cost is not any greater than the above types, but there are lots more cells both in series and parallel to achieve greater duration and amp discharge. My two packs of 3S4P in series have put out over 70 amp bursts and provide incredible power...

    I guess the thing to remember with lipos is the voltage...It's really the only confusing cross-over from cads and nihms.
    Hot off the charger, each cell is 4.2 volts, but drops to 3.7 under load. they also put speed controllers to work hard.

    Good luck!

    Rob

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    Aero330LX's Avatar
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    Li- Poly

    Hi Rob,
    This is a trainer that I have had sitting around for a long time. Actually I've had it for about 19 years. It's an MEN (see my previous post for more info.) trainer that I was gonna fix up for my Father to fly some. I was wanting to go with these Li-Poly's to learn some about them so I could build a few of those electric 3d deals for some late night 3d, and Dad was wanting to get into it so I thought this one would be a good one to do this with. I've received lots of great info. and appreciate it. Thanks guys!

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    Li- Poly

    I'd have to say that lithiums are safe as long as you have the correct setup. This is a great place to learn what is required to use them and how to use them.
    In general, most park flyers will use a 2S (2 cells in series) yielding 7.2volts. What you really have to watch for is the amperage that the motor will draw, this is vital to the life of the pack. A 2S Etec 1200mah will be good for 6 to 7.2 amps and short bursts of 8.4 to 9 amps. Ideally, you want to keep the draw around 4 or 5C (C = capacity in mah, in this case 4x1.2=4.8 or 5x1.2=6amps). To handle higher current, you connect packs in parallel, this will yield 7.2volts but capacity is doubled to 2400mah and capable of supplying 12 to 14.4 amps continuously and short bursts of 16.8 to 18 amps.
    To get higher voltage, add one more cell to the pack, ie 3S, so now 3 cells connected in series. This results in a nominal 10.8volts but only supplies the same 4.8 to 6 amps. A 3S or 3S2P is good for smaller brushless motors like Astro 010. The 2P after the 3S notes that there are two three cell packs connected in parallel, thus doubling the capacity and current load.
    Hope this all makes sense and I didn't confuse anyone. To make this easier, it would be easy to recommend what would be needed as far as lithium packs if a specific motor was given.


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