Li poly's vs: Li Ions for RX packs

[fishgod at pobox.mtaonline.net]

Troy,
Very good point.  I guess I was thinking about the loads that all the
digital servos in an IMAC plane put on batteries.  They can easily stall
digital servos causing huge loads.

Michael Laggis
NSRCA 3618  





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



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