Li poly's vs: Li Ions for RX packs

[Troy Newman]

2C is a huge load and there is no way that your plane as a RX pack should
ever see that kind of load.

the Li-ion pack are 2000mah....and you are talking of a 4amp or 4000mah
load....now maybe on an electric plane with a BEC and all digitals....yes
the load will be up past this....

A reference. YS 140DZ on a Hyde ARA mount, All the best digitals you can
use. High Speed, super tight deadband stuff. 9411's...8411s...8417s and even
a digital mini on throttle 3421s

 I'm drawing 170-200ma per flight...flights are about 10-13mins. So take
this too its worst and say 200ma per flight that is 1/10thC or 0.1C...this
F3A stuff with the snaps and stuff that come with it.

What I have found is for the size pack we are dealing with for RX operation
the weight savings are minimal for Li-ion to Poly to change....a 2000mah
Li-ion pack is 3.4oz...a 1900mah 2 cell Li-Poly weighs in at 2.8oz....On my
scale... S0 you are saving about 1/2oz total....but you are gaining about
$15 in price tag too. $35 for the Li-ion and $50 for the Poly.....40%
increase in costs to get a high draw battery when you are not even the
current Ion cells to their max draw capability.


Don't get me wrong I think the poly's are a great pack and they will only
get better......I just don't think at this point in time you should run
anything less than 1900 or 2000mah for a RX pack because weight is not an
issue at this size level....So you go to a 1300mah pack and cut your flying
almost in 1/2..to save 1oz...and the differences in Ion-vs Poly at this
level are very very minor in terms of physicals.

The question comes down to are the Li-ions dead technology because the Poly
has some minor weight savings at this small level and we should just start
switching over to Poly's all the way...I don't know. I would not say they
are "any wiser or any worser" (Ali Quote)  in terms of application of the
battery.

Now in the Electric powered model the Poly has the huge advantage of the 6C
power draw.....Especially in an E Pattern model....42Volts pulling
50-60-80amps then I can certainly see for sure that the poly is the pack of
choice. That extra 1/4-1/2 oz per cell adds up when you are talking 11 cell
packs and also 8000mah.


I'm not so sure the Ions don't still have a place in our systems...I have
been using them now over a year..with lots and lots of flights on a couple
Li-ion packs. In my opinion they are the best battery setups I have ever
run. The NMP packs and Charger from Central are 100% dummy proof. We have
tried to mess them up and to no avail.....You plug them up and everything is
setup and done...no nothing special required. Can't overcharge the cells
this is where the safety stuff comes in.....and they are better than Nicds
as for safe and easy operation. The discharge curves are superb and very
linear...not the peak and false peak stuff Nicds and Nimh's go
through.....Its simple....its like a fuel tank....Plug the tank in and
re-fuel the battery....As it drains down the tank tells you where it is
exactly......its just your fuel gauge on your car.


Simple and easy.


Troy Newman


----- Original Message ----- 
From: <fishgod at pobox.mtaonline.net>
To: <discussion at nsrca.org>
Sent: Monday, January 26, 2004 9:40 AM
Subject: Li poly's vs: Li Ions


With my experience with Li-poly and Li-Ion I would have to assume that the
high current Li-poly's would be a better choice.  The standard Li-ions
cells are only good to 2c and that is putting a pretty healthy load on
them.  While the new high current Li-poly's are rated at 6C for 80% of the
capcity.  With the demands of digital servos I would think that the poly's
would be a better choice.  Of course I am no battery expert this is just
from my experience with small electric planes.

Michael Laggis
NSRCA 3618






Li-poly's work. They seem to work as well as Li-ons.  They are being sold
as RX packs as well as electric motor packs.

That being said, I have noticed that my Li-poly's drop off a little after
being fully charged, I have not yet tested how long they hold their charge
before they are used.

In the final analysis, if they work well, then they are lighter and thus
attractive to pattern players.

Regards,

Eric.


 -----Original Message-----
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]On
Behalf Of mike mueller
Sent: Monday, January 26, 2004 8:52 AM
To: discussion at nsrca.org
Subject: Li poly's vs: Li Ions


 Last year I ran a 2 cell 7.4  2000 mil. Li Ion pack in my plane. Since
then I've been building small E. planes and have gotten used to the newer
technology of Li poly's. My question to all you experts is should all my
new receiver battery packs from here on be Li Poly's? Does anyone see an
advantage or disadvantage to this. The setup I thought would be best was a
7.4v  2100 Mil 2S Thunder Power Li Poly with the appropriate 5.3 regulator
( what's your suggestion?) for 5 JR digital servos and a Jr pcm receiver.
If this has been asked before I apologize I just havn't seen it discussed.
Also I have a Triton charger so that's not an issue. Thanks, Mike


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