News on Lipo cells

[gonper]

OK, I am almost ready for sell some Lipo cells.

I am receiving a small bunch of cells in the following days, they are very especial cells, high energy density cells (around 200W/Kg) perfectly suited for SC size requirements (see pictures)

Specs:
Sizes: 6.8x49x135mm
Volt: 3.7V
Capacity: 5000mAh (all samples we have tested have charged/discharged over 5400mAh)
Weight: 100gr
Maximun continous discharging rate: 4C / 20A (manufacturer claims up to 6C but per my tests they are good up to 4C over that voltage droops too much but cell can handle more with out damage)
Terminals: Tin tabs (easy to solder with normal SnPb hot iron solder)
They fit in standar ECO battery holder and other SC size battery holders [img]/ubbthreads/images/graemlins/cool.gif[/img]

For the ECO 8 I think that best are packs:
3S2P (600gr, 11.1V, 10000mAh, up to 40A/444W)
4S2P (800gr, 14.8V, 10000mAh, up to 40A/592W)

Just for reference:
A normal 3300mAh 10 SC cells Nimh pack weights about 625gr.
Avarage Eco 8 consumition is 13A/17A

Price:
30.00 Euros per cell (sorry no packs made yet...)
Around $36.60 per US people [img]/ubbthreads/images/graemlins/smile.gif[/img]

You can place orders now if you like here or by gonzalo.chomon@rcmaterial.com or send me a PM

I will have more sizes in close future, special for Piccolos are in my order list as well...




More news:

I am working in a new Lithium tecnology whit another manufacturer, I will receive first samples in the following week the special features of this new technology is safety, this cells do not explode or caugh on fire if over discharged or crunched or what ever you do to them...
As well they can be charged with normal Nimh charger, up to 1500 cicles if well treated and 2C charges are posible.

They are testing now how they do handle deep discharges... will let you know about this when info relased I will make my own test on this matter as well.

This first samples are up to 4/5C next ones will be up to 8C and specialy designed for RC use [img]/ubbthreads/images/graemlins/cool.gif[/img] as the engeneer manager is a electric RC pilot [img]/ubbthreads/images/graemlins/cool.gif[/img] so he knows our needs...
First of this cells will be available for testing in 3 months and will be on sale in about 4 if good results are obtained from the tests.

I am writting down a big article about Lipo cells, their use, how to make packs, safety, etc. that will be available in the DM site next week (more less) there will be very interesing info there never released before [img]/ubbthreads/images/graemlins/cool.gif[/img]

[gonper]

[Erez]

Gonzo, sounds great, but they better test that very very thoroughly before claiming they can be charged by nimh chargers. Also, lithium is explosive when it comes in contact with oxygen, so its impossible to take out all risk, but its good you're thinking about safety.

I just got this in my email from AMA, thought it would be a good place to post it. A friend of mine had a fire with a small pack and had a 3 foot orange fireball, which melted nearby servos into a puddle. So, please be careful with these cells. Lithium batteries are awesome, but require some additional precautions.

EMERGENCY SAFETY ALERT

Lithium Battery Fires
Lithium batteries are becoming very popular for powering the control and power systems in our models. This is true because of their very high energy density (amp-hrs/wt. ratio) compared to NiCads or other batteries. With high energy comes increased risk in their use. The, principal, risk is FIRE which can result from improper charging, crash damage, or shorting the batteries. All vendors of these batteries warn their customers of this danger and recommend extreme caution in their use. In spite of this many fires have occurred as a result of the use of Lithium Polymer batteries, resulting in loss of models, automobiles, and other property. Homes and garages and workshops have also burned. A lithium battery fire is very hot (several thousand degrees) and is an excellent initiator for ancillary (resulting) fires. Fire occurs due to contact between Lithium and oxygen in the air. It does not need any other source of ignition, or fuel to start, and burns almost explosively.

These batteries must be used in a manner that precludes ancillary fire. The following is recommended:


Store, and charge, in a fireproof container; never in your model.

Charge in a protected area devoid of combustibles. Always stand watch over the charging process. Never leave the charging process unattended.

In the event of damage from crashes, etc, carefully remove to a safe place for at least a half hour to observe. Physically damaged cells could erupt into flame, and, after sufficient time to ensure safety, should be discarded in accordance with the instructions which came with the batteries. Never attempt to charge a cell with physical damage, regardless of how slight.

Always use chargers designed for the specific purpose, preferably having a fixed setting for your particular pack. Many fires occur in using selectable/adjustable chargers improperly set. Never attempt to charge Lithium cells with a charger which is not, specifically, designed for charging Lithium cells. Never use chargers designed for Nickel Cadmium batteries.

Use charging systems that monitor and control the charge state of each cell in the pack. Unbalanced cells can lead to disaster if it permits overcharge of a single cell in the pack. If the batteries show any sign of swelling, discontinue charging, and remove them to a safe place outside as they could erupt into flames.

Most important: NEVER PLUG IN A BATTERY AND LEAVE IT TO CHARGE UNATTENDED OVERNIGHT. Serious fires have resulted from this practice.

Do not attempt to make your own battery packs from individual cells.

These batteries CANNOT be handled and charged casually such as has been the practice for years with other types of batteries. The consequence of this practice can be very serious resulting in major property damage and/ or personal harm

Safety Committee
Academy of Model Aeronautics

guess you didn't read tony's post erez

[ccarlson]

Heh heh... They add a bit of clutter, but my guess is more posts with the safety information are better than fewer.

Has anyone on the board encountered a severe issue with LiPo packs?

[ QUOTE ]
Has anyone on the board encountered a severe issue with LiPo packs?

[/ QUOTE ]

Yes, my wife cut my throat seeing CC statement with lot of LiPoly order in it [img]/ubbthreads/images/graemlins/grin.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img]

>>Has anyone on the board encountered a severe issue with LiPo packs?<<

No, actually I purposely tried to destroy some lipoly cells by shooting a pellet gun at it. I got a lot of smoke but no fire. I also tested one cell by shorting it outdoor. No fire either.

I crashed with a 12000 mah pack and destroyed the bottom cell. Not smoke or fire either.

That is not to say that lipoly is not dangerous. They are dangerous but they are also a bit more robust than most people think.

The idea is to use your judgement and handle with care.

[hendrix]

I have used many lipo packs and i shorted one of them but
i haven't see anything soooo dangerous.
Of course if you short even a car battery you can cause explotion but i haven't seen anything saying that you cant replace your car battery on your own.
If someone is so stupid then he must have bigger problems than that.
Chris

[gonper]

</font><blockquote><font class="small">En respuesta a:</font><hr />
Gonzo, sounds great, but they better test that very very thoroughly before claiming they can be charged by nimh chargers. Also, lithium is explosive when it comes in contact with oxygen, so its impossible to take out all risk, but its good you're thinking about safety.


[/ QUOTE ]

As I said it is a different chemistry, Lithium is involved in it but it is not the same as Lipoly that we know now.
I can not tell you much more because of two things, one is that I am not a expert on those and as well because I signed a confidenciality contract with them and I dont know if already I have give out to much information [img]/ubbthreads/images/graemlins/blush.gif[/img]

Actually they can be charged with Nimh charger that is not a problem with them, even they can be charged with any charger program up to 4.2V the problem is the charger will not know when to stop...
So is recomended to use Li charging programs with voltage detection cut off and as well battery will last longer this way.

I will test some of them next week, so I will post results here.

I have been torturing manny Lipo cels and I had no problems so far.

I do not think they are as fragile as they want us to think, even I think that that warming from AMA is too much, they are trying to scare people as manny times happens in US

Why do not AMA try to overcharge a NiCd cells and then punch them [img]/ubbthreads/images/graemlins/shocked.gif[/img] or even better do it with a acid cell [img]/ubbthreads/images/graemlins/grin.gif[/img], resultsaare pretty similar...

This is just my opinion do not get me wrong please. [img]/ubbthreads/images/graemlins/smile.gif[/img]

&gt;&gt;actually I purposely tried to destroy some lipoly cells by shooting a pellet gun at it.

Bones you must be loaded (excuse the pun!) [img]/ubbthreads/images/graemlins/smile.gif[/img]