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Li- Poly - 6/28/2003 2:20:50 AM   
Aero330LX



Posts: 450
Joined: 4/6/2002
From: None, USA
Status: offline 		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.
       Post #: 1

Li- Poly - 6/28/2003 4:11:29 PM   
BlackCloud



Posts: 749
Joined: 5/23/2003
From: Hollywood, FL, USA
Status: offline 		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

(in reply to Aero330LX)
       Post #: 2

Li- Poly - 6/29/2003 8:29:48 PM   
Steve Neu


 

Posts: 70
Joined: 6/19/2003
From: San Diego, CA, USA
Status: offline 		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

(in reply to Aero330LX)
       Post #: 3

Li- Poly - 6/29/2003 9:14:51 PM   
d_wheel



Posts: 571
Joined: 1/27/2003
From: Deep in the Heart Of, TX,
Status: offline 		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.

(in reply to Aero330LX)
       Post #: 4

Li-poly - 6/29/2003 9:46:46 PM   
modest-master


 

Posts: 109
Joined: 1/12/2002
From: Florida
Status: offline 		Check [url]www.EspritModel.com[/url] web site for more information.
We have them in stock.

_____________________________

If you need help!!!!!!
www.espritmodel.com

(in reply to Aero330LX)
       Post #: 5

Li- Poly - 6/29/2003 10:50:37 PM   
Steve Neu


 

Posts: 70
Joined: 6/19/2003
From: San Diego, CA, USA
Status: offline 		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

(in reply to Aero330LX)
       Post #: 6

Li-poly - 6/29/2003 10:58:12 PM   
modest-master


 

Posts: 109
Joined: 1/12/2002
From: Florida
Status: offline 		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

(in reply to Aero330LX)
       Post #: 7

2x3S4P 7800mAh Li-poly batteries. - 6/29/2003 11:49:22 PM   
d_wheel



Posts: 571
Joined: 1/27/2003
From: Deep in the Heart Of, TX,
Status: offline 		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.

(in reply to Aero330LX)
       Post #: 8

Re: Li-poly - 6/30/2003 5:18:07 AM   
Steve Neu


 

Posts: 70
Joined: 6/19/2003
From: San Diego, CA, USA
Status: offline 		[QUOTE]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 [/QUOTE]

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

(in reply to Aero330LX)
       Post #: 9

Li- Poly - 6/30/2003 10:01:37 PM   
Dave Lilley



Posts: 109
Joined: 6/4/2003
From: Schertz, TX, USA
Status: offline 		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.com/pdfs/cxnews/CX18%20Li_Ion_Polymer%20Focus.pdf
http://www.panasonic.com/industrial/battery/oem/images/pdf/li-poly.pdf
http://www.panasonic.com/industrial/battery/oem/chem/lithion/index.html
http://www.virtintern.duke.edu/nokiateam/batteries.ppt
http://www.canyonriver.com/information_battery.html

Dave Lilley

< Message edited by Dave Lilley -- Jun 30 2003 5:18PM >

(in reply to Aero330LX)
       Post #: 10

Li- Poly - 6/30/2003 10:21:04 PM   
Steve Neu


 

Posts: 70
Joined: 6/19/2003
From: San Diego, CA, USA
Status: offline 		[QUOTE]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 [/QUOTE]

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

(in reply to Aero330LX)
       Post #: 11

Li- Poly - 6/30/2003 10:43:25 PM   
Dave Lilley



Posts: 109
Joined: 6/4/2003
From: Schertz, TX, USA
Status: offline 		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.

(in reply to Aero330LX)
       Post #: 12

Li- Poly - 6/30/2003 10:57:44 PM   
Steve Neu


 

Posts: 70
Joined: 6/19/2003
From: San Diego, CA, USA
Status: offline 		[QUOTE]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.
[/QUOTE]


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

(in reply to Aero330LX)
       Post #: 13

Li- Poly - 6/30/2003 11:33:35 PM   
Dave Lilley



Posts: 109
Joined: 6/4/2003
From: Schertz, TX, USA
Status: offline 		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

(in reply to Aero330LX)
       Post #: 14

Li- Poly - 6/30/2003 11:44:34 PM   
Steve Neu


 

Posts: 70
Joined: 6/19/2003
From: San Diego, CA, USA
Status: offline 		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

(in reply to Aero330LX)