Lipo's at the NEAT Fair - RC Groups
Thread Tools
Sep 13, 2003, 06:52 PM
Registered User
jimsp's Avatar

Lipo's at the NEAT Fair


Just got back from a day at the NEAT fair – a fabulous event! Couldn’t help but notice that Lipo’s were everywhere. I remember last year they seemed to be confined mainly to FMA booth that was drawing a lot of attention with their display of high current Kokams. Most notable this year was that almost all of the planes flown in the very impressive demo’s were using Lipo’s. This included planes ranging in size from a wingspan of 6” to a wingspan of 80”. Earlier, on a slightly sour note for Lipo’s, a B-17 that was having its Lipo’s charged while in the plane caught fire.
Sign up now
to remove ads between posts
Sep 13, 2003, 11:23 PM
Registered User
dadspet's Avatar
FMA rep at the NEAT fair claimed that all the Lipos they got in last week will be good for 10C. They haven't updated their web site yet but will soon. He claimed they have been conserative on their lipos and wanted to wait for more testing before they made the claim. Not sure if this is just BS or not or if they are just updating the "spec" on their current lipos with no change in actual product. Stay tuned I guess and let the jury decide.
Sep 14, 2003, 12:40 AM
Registered User
Andy W's Avatar

Re: Lipo's at the NEAT Fair


Quote:
Originally posted by jimsp
Earlier, on a slightly sour note for Lipo’s, a B-17 that was having its Lipo’s charged while in the plane caught fire.
Sigh..
Sep 14, 2003, 12:53 AM
That is terrible indeed about the B-17....

However I did read a more detailed report about the incident. I guess the owner was topping off his 2 cell pack inside the airplane - however he had been charging lots of 3 cell packs prior and had left the charger on the 3 cell setting! Of course as we al know, charging a 2s LiPo pack on a 3s setting is not a good thing. We can never forget that as wonderful as LiPos are, they still must be treated with the utmost of respect!

I wish I could have been at NEAT. Sounds like LiPos are stealing the show from every brand! Cant wait to see more detailed reports and pics which Im sure we'll see tons of this week and in the next few mags

Jason
Sep 14, 2003, 07:53 AM
Registered User
Andy W's Avatar
(charging 2 cells on 3-cell setting) .. better ..

..a
Sep 14, 2003, 10:06 AM
Registered User
jimsp's Avatar
Multi-function chargers are fine but it is easy to make mistakes as in this example. I think one of the safest(and also inexpensive) ways to charge the Lipolys is to use DIY chargers such as this one or others that have been covered in the discussion groups. Because you can make them for around $5 you can make several and dedicate them to charging a particular type packs. On the outside mark in big letters what the charger is for. Below is an example of what I mean. It is a charger set for charging my 2 cell 1200mah lipoly packs.

Please if you don’t have a clue about electronics don’t attempt to build these chargers. Have a knowledgeable friend do it for you.
Sep 14, 2003, 06:59 PM
Build'em and Crash'em
Ken Lapointe's Avatar
There was another Li-Poly incident at NEAT besides the B-17 problem.

A very small bi-plane, about a 1 ft wingspan, was just sitting in a van and caught fire Saturday during the demos. It had been flown hours before and was partially discharged. It was NOT on a charger. Luckly for the owner the grandson saw the smoke , saw the plane burning and pulled it out of the van. Lucky for me too, cause my van was right next to his. The rug on the van had just started to burn.

These were very small cells, I think 2 of them. I can only imagine the damage if the were bigger cells.

Ken
Sep 16, 2003, 05:45 AM
Registered User
David Kyjovsky's Avatar
Quote:
Originally posted by jimsp
Multi-function chargers are fine but it is easy to make mistakes as in this example. I think one of the safest(and also inexpensive) ways to charge the Lipolys is to use DIY chargers such as this one or others that have been covered in the discussion groups. Because you can make them for around $5 you can make several and dedicate them to charging a particular type packs. On the outside mark in big letters what the charger is for. Below is an example of what I mean. It is a charger set for charging my 2 cell 1200mah lipoly packs.

...
Exactly! As I charge both 2s and 3s pack on dedicated chargers, I painted the (JST) connectors for 3s (both on the charger and on the packs) black with permanent marker. Now if I ever try to charge 2s pack from the 3s charger, putting black connector into red female should catch my attention.
Sep 16, 2003, 09:16 AM
Registered User
dhurd's Avatar
Some of us were discussing these incidents at NEAT. I didn't get to inspect the packs so I can't say this is exactly why the Lipo's caught on fire but we came up with a possible cause by applying a few assumptions. We use single cell Lipo's in our application (our receiver runs on a single cell) and have never had one catch fire due to abuse from overcharging or discharging them too deeply. I HAVE had them get hot and expand due to these conditions. When Lipos expand the polymers seperate and break the circuit thus preventing the offending condition to continue. This is why Lipos are much safer then LiIon. Lipos are in a envelope that will expand when the cell is abused. LiIon must be contained within a rigid metal casing so for it to expand it vents (sometimes expolosively) and the free Lithium will burn when combined with oxygen. Anyway, I think the problems are arising because the multi cell packs are wrapped in shrink wrap which prevents the cell from expanding and breaking the circuit. In other words the shrink wrap is overcoming an inherent safety feature of Lipos. I would suggest when making a multi cell pack creating some sort of "weak" spot in the shrink wrap that will allow the cell to expand if it is abused.
Again this conclusion is arrived by a few assumptions and personal experience and it may not be the actual cause of the incidents.

Dan Hurd
DWE
www.smallrc.com
Sep 16, 2003, 04:04 PM
Old Desert Rat
Arizona Chuck's Avatar
dhurd, that is the reason I use cheap electrical tape to wrap the packs. The heat will soften the tape and let it expand. Ask me how I know!! I have puffed two packs with my Orbit charger using the 3 cell setting on 2 cells, never had anything close to a fire.
Sep 16, 2003, 04:08 PM
BEC
BEC
Registered User
BEC's Avatar
The small airplane fire was said to be due to a short circuit. I saw the remains but the owner was not entirely sure about why it shorted out (or even if it did).
Sep 16, 2003, 04:31 PM
Registered User
Alan W's Avatar
I heard a very distinguished bearded gentleman say something quite funny this weekend at NEAT

"I call Lipo's Ball park Franks.....why ?? They Plump when you Cook'em!!!"

Sep 17, 2003, 07:06 AM
Build'em and Crash'em
Ken Lapointe's Avatar
Quote:
Originally posted by BEC
The small airplane fire was said to be due to a short circuit. I saw the remains but the owner was not entirely sure about why it shorted out (or even if it did).

Otherwise known as "I have no idea what happened"

Ken
Sep 17, 2003, 09:23 AM
Registered User
dhurd's Avatar
A short will also result in the "puffed up" state and should have broken the circuit. So I would still suspect the fact that it was shrink wrapped thus not allowing the polymers to seperate as the culprit and not the cells directly.


Thread Tools