[NSRCA-discussion] LI-IO packs

Thu Oct 31 13:54:54 AKDT 2013

Lithium ion (LiIo) cells are more rugged than lithium polymer.  I won't use lipo receiver batteries in a fuel airplane because of the aluminum foil tabs that serve as positive and negative terminals.  Seen too many failures.  I used lithium ion batteries from Central (NMP) when I flew YS.  Never had a failure due to the cells themselves.  Lithium ions will still burn if overcharged, but mechanically are much more rugged.  As Jim Oddino said, lipos are good for fast discharging.  LiIo's are great for less demanding current draw, such as receiver/servo packs.  Even with a regulator, they are still lighter than NiMh packs.  The LiIo cells sold for RC use are identical to those used in most laptop computers, although newer ultrathin laptops have started using LiPo's.

For a long time, 2 cell Lilo packs came without balance plugs.  Later ones from NMP do.  I recommend balance charging 2 cell lithium ion packs at least occasionally, because a few I've had have gone out of balance.

Jon

-----Original Message-----
From: Scott McHarg <scmcharg at gmail.com>
To: General pattern discussion <nsrca-discussion at lists.nsrca.org>
Sent: Thu, Oct 31, 2013 4:33 pm
Subject: Re: [NSRCA-discussion] LI-IO packs

They came with the plane?  :)

On Thu, Oct 31, 2013 at 4:23 PM, John Gayer <jgghome at comcast.net> wrote:

No, Lithium-Ion cells appear to be expensive, heavy lipos. both seem to charge to approximately 4.2.
http://en.wikipedia.org/wiki/Lithium_ion_battery#Charge_and_discharge
http://en.wikipedia.org/wiki/Lithium_polymer_battery

There appears to be a weight and price penalty associated with the litium-ion battery over the lithium-polymer battery with no benefit. Perhaps someone can explain the popularity of lithium-ion?
John
On 10/31/2013 1:21 PM, joddino at socal.rr.com wrote:

---- Daniel Dupont <dansy44 at gmail.com> wrote:

So Jim if I understand correctly Lithium-ion cells are basically cheap
Lipo¹s?

Hum I always believed they were a slightly different technologyŠ.

Daniel on MacBook Pro

On 10/31/2013, 1:46 PM, "joddino at socal.rr.com" <joddino at socal.rr.com>
wrote:

---- Scott McHarg <scmcharg at gmail.com> wrote:

Morning y'all,

I've spoken to a few people about charging Lithium Ion packs but we did
not
arrive at a definitive answer.  I need to understand what the best
solution
(besides buying another charger) is for my situation.

I consider myself fairly knowledgeable about the Cellpro 10XP.  Usually,
it's me giving the help but I'm not sure what to do here.  Here's the
scenario:

  Cellpro 10XP Multi-Chemistry Charger.  The User Manual and everything
about the charger says that it can charge the ION packs.  So, I go to
program a preset for this but in the software, there is nothing that
says
anything about ION packs.  There is LiPo, Pb, A123, Ni-Cd, and Nickel
Metal.  I have some ION 7.4V 5200mah packs that I need to charge and a
2600mah pack for the ignition on a 42% Edge 540.  The packs are made of
4
cells but are wired so that they are only 2 (2 in series, 2 in parallel)
cells.  As close as I can tell, I should select the LiPo 2sU (2 cell
unbalanced) but I don't want to make a mistake.  Someone told me that
would
be OK and another said that if you program the charger by the charger
instead of the software, there is an ION setting but I haven't confirmed
that yet as it was late last night when I was checking.

Anyone have any idea what to do to charge these packs?

Thanks,

-- 
*Scott A. McHarg*
Sr. Systems Engineer - Infrastructure

If they are lithium-ion cells they should be charged to 4.2 volts per
cell or 8.4 volts for a 2s pack.  Lithium polymer cells are lithium ion
and are charged the same.  My Cellpro charger charges to 4.204 volts per
cell when set for LiPo packs and that is what should be used for Lithium
ion.  The Lithium ion cells generally have higher internal resistance and
therefore can not be discharged or charged at high rates.  I use one C
max.

Jim O
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The first Li-Ion cells used in the RC industry were packaged in metal cylindrical cans similar to NiCds.  Then the packs packaged in flexible plastic sacks arrived for use in powering motors.  These came to be referred to as LiPo packs but basically used the same chemistry but also had the advantage of having low internal resistance.  Since those early days many other chemistries with different fully charged voltages have arrived and many charger suppliers have tried to cover them as well.  The voltages printed on the packs are typically a nominal voltage and might be 7.2, 7;4 or 7.6 volts even though the full charge voltage is 8.4.  I suspect the cells referred to here have the metal cans and that is why they are described as Li-Ion.  Hope this helps.

Jim O

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-- 
Scott A. McHarg
Sr. Systems Engineer - Infrastructure

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