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What "C" (amperage level) should I target??
First, keep in mind that all "C" are NOT created equal. What
really matters
is Watts ( = Current*Voltage), and the Hyperion VX deliver extremely high
voltage, for more power at any "C".
Second, you should know that many cells on the market today are over-rated. That
is, if you run at the true continuous max rate sugggested, not only will voltage
performance be poor, but the pack won't last very long.
For the VX series, we decided instead to do a lot of testing to see what results
we got based on the number of usable cycles the pack could make at various "C"
rates. We found that choosing a prop at 15C to 20C static (tested on the
ground with fully-charged pack) was the "sweet
spot", in which you can expect over 200 cycles with marginal loss in performance.
In fact, the cells deliver so near 100% capacity when new, that you can
outperform many other brand-new "high rate" packs even after you've got a 100+
cycles on the VX!
Our Hyperion VX type batteries are properly rated
for 20C continuous. You may even prop for higher peak current draw in
models using a lot of throttle management, like E3D, when and if necessary.
Does that mean "I should prop for 20C+!"?
Maybe....but maybe not! To decide what rate is appropriate
you should use good sense, based on the facts, to meet your performance
goals and match your model type!
At true 20C continuous, you'll get a safe-margin flight time of about 2.5
minutes max. At 15C continuous, that stretches to more than 4 minutes,
and the battery lifespan is longer.
Assuming your model and flying style call for various power settings, propping
your model such that 15~20C static is obtained on the ground means that your
flights will likely average 6 to 12 minutes, or even more, as average discharge
rates are lower than peak. That's where
we fly most of our own models on Hyperion VX packs: set for
12C~20C static on the ground, depending on model type.
Please pay particular attention to this part:
ANY batteries, NiCd, NiMH, or Lithium Polymer, from ANY manufacturer
will show the same characteristics when run at lower than their peak continuous
rating: They will deliver more voltage throughout the discharge, more
capacity per each discharge, and they will last more charge/discharge cycles.
Keep in mind, also, that many models will not
balance properly if you use the lightest possible Lithium battery. Take a
typical "Speed 400" direct drive model, for instance. You may be tempted
to select the lighest possible pack, and run it at the pack's max continuous
rating. But most S400 models were designed around 7 to 8-cell
packs of 500AR NiCd cells, which weigh 140-165 grams. Result: you
are running your Li-Po battery at its rated continuous limit, and you have to
add lead to the nose of the model to get the balance right. Not the best
solution! Instead, consider something like the LVX1500-2S pack, which has
almost identical form to a 7-cell 1000mAh NiMH pack. It weighs 80 grams,
and that may be enough to get your model balanced (or require a minimum amount
of lead added, anyway). Now you are running the pack at 8C, for these
advantages: (1) Higher delivered voltage [= POWER] (2) Nearly twice the
run time, or two flights without re-charging (3) longer pack lifetime. In
fact, the voltage of the VX pack will be so high at this reduced rate that it
will can exceed the voltage of a 7-cell NiMH pack! If
you are running a geared S400 model, or brushless, you can take this even
further by going to a 3S 1500 pack, and (1) be just about guaranteed the model
will balance without additional weight and (2) get up to 50% more peak power output
(because you added 50% more cells!). Of course, some models, especially
those specifically designed for Lithium cells, can balance with the lightest
pack - so just remember to think the "balance" issue through before you
choose....
General Tips:
Caution! Hyperion VX Series packs retain
high voltage under load. That means that when switching from
a lower-rated pack type to VX series, your motor will likely draw more
current with the same prop. In fact, it can be as much as 40% more
amperage!! That may be too much for your motor, and therefore cause
over-heating and damage. Without a diagnostic tool such as the Hyperion
Emeter to check current draw, you are really "flying blind",
so please check that current draw!
If you are converting an
existing model from NiMH batteries to VX Lithium packs, for example, you should plan on supplying
nearly the same voltage with lithium cells, or more, and changing propeller,
gearing, or motor type if required to attain your target "C" rate.
Target Rates: A static discharge on the ground with freshly charged VX
pack of:
8C to 12C: For slowflyer or long-duration models
12C to 15C: For most sport and scale models out there, this give excellent
performance and long flights
15C to 20C: Extremely aerobatic models and EDF jets
20C to 25C: Pylon racing competition
20C to 30C: May be "best" for some competition classes, particularly club glider
events
To get the most from your high
output batteries, you’ll need to match the battery size and arrangement
to your model’s power system. If
you haven’t got the tools (see the Hyperion Emeter) or experience necessary
to do that, then we STRONGLY urge you to seek assistance from experienced
modelers.
Series and Parallel?
Lithium batteries can be
connected in series to increase voltage, and series packs can be connected in parallel
to increase capacity (and therefore the maximum current available – remember
“C”).
A pack of 3 cells in series (3S1P, or simply "3S") has 3x1= 3
cells. This pack has NO parallel connections.
If you take two 14.8V "4S1P" packs (HP-LVX2500-4S, for example) and wire them in parallel, it would be designated "4S2P", have
8 cells in the
assembled pack (4S*2P=8), have 5000mAh total capacity, and be charged at the same
14.8V "4-cell"
setting as before.
Manufacturers recommend that Lithium Cells be charged at "1C" rate;
0.8A for a
LVX0800 pack, for example. You can charge at lower rate but it will take
a little longer, or up to 1.5C rate without harm if your charger does not have
the exact setting you need for 1C.
"S" affects charge VOLTAGE:
A 2S pack
is ALWAYS charged at 2-cell setting, "3S" at 3-Cell, etc...
"P" affects max charge (and discharge) CURRENT:
A 2500-4S2P assembly has
5000mAh (5.0A) capacity, so recommended "1C" max charge current is 5.0A
An example: A larger model may use an assembly
of "10S2P" VX 2500mAh
(a total of four VX2500-5S packs, or 20 cells)
- Multiply the "S" value of this pack by the nominal voltage
for one cell (3.7V) to get the nominal voltage for the pack:
10S x 3.7V = 37.0V
- Multiply the "P" value by the capacity for
one cell to get total capacity of the pack:
2P x 2500mAh = 5000mAh
- Multiply "C" ratings by the capacity of the new pack (5.0Ah) to get
rates:
12C x 5.0A = 60.0A (a sensible max current level for many large brushless
motors in sport models)
16C x 5.0A = 80.0A (for models like F3A aerobats, ducted fan jets,
etc...)
ADVISORY: In the
past, lithium batteries were rated for 8C to 12C, and even at those low
rates delivered much less than rated capacity and voltage. The
solution then was to build complex "parallel" packs with capacities up to
8000mAh, so that at 60A average current the pack was drawing about 8C and
provided reasonable voltage and delivered capacity.
The Hyperion LVX Series, however, deliver high voltage and capacity even
when propped for 20C static. With capacity up to 3700mAh available, we
have found that almost every class of model can (and usually should) be
flown WITHOUT parallel connections at all. Larger models, using motors
like the Z40 Series from Hyperion, are usually at their best when drawing
current from 40A to 75A. "E3D" models are on the extreme end of max
power requirements, so let's use that as an example. We have a 73" YAK
54 E3D model which uses Hyperion Z5025-20 motor and 10S lithium. Max
current static on the ground is 70A (~20C for the LVX3700), for about 2400W
input power. We chose LVX3700-5S and wired two packs in series, so we
have 10S (37V nominal) and 3700mAh capacity. Flown in an E3D routine,
flight time is 5 to 6 minutes.
The same pack used in large sport planes pulling 65A peak can give aerobatic
flights of 6 to 12 minutes, depending on pilot style.
The important part is that the 3700mAh pack is extremely
light, so the models fly much better all around, and use less power to do the
same manuver compared to carrying a higher capacity pack. Rather than
loading your airplane with a lot of extra battery for the whole flight, get more
flight time by keeping the plane light when it flies, and a second pack on the
charger while you are flying! Same cost as a 2P pack, much better performance,
and more total flight-time.
The vast majority of large models fly extremely well on
"1P" packs of LVX3300 to LVX3700 cells. Motors are more efficient, in
general, when using higher voltage and less current - so if you need more power
add more cells rather than more capcity and current...
For very large models, of a competition event when a certain flight time is
required, you may want to parallel Hyperion LVX2500, LVX3300, or LVX3700 packs.
In that case....
Should I use a pre-asssembled "unit" pack or wired
individual packs?
We recommend that individual packs be harnessed or wired together,
in series or parallel, whenever you need to increase voltage or capacity.
Compared to a single "unit" pack, harnessed packs have these advantages:
1) Easy to check, easy to balance, easy and safe to charge:
Two packs harnessed in parallel - for example 2200-3S to achieve a
3S2P, 11.1V 4400mAh pack - can be disconnected at any time, so you retain
the ability to check each individual cell through the multi-connectors, and
to charge safely by separating the packs and using PCM Guard or Balancer
devices. If you have a "hardwired" parallel pack in a single unit, you
don't have the ability to clearly diagnose a single weak cell in the pack.
2) Easy to separate for use as a single pack: If you
decide to retire that big model, you can instantly revert your 3S2P pack to
a pair of 3S packs, for use in a smaller model.
3) Easy to re-wire. Need to convert that 3S2P pack into
6S? With a harness, it's a snap. A hardwired pack would likely
be damaged in the arduous job of re-soldering the individual cells, as
required in such a conversion.
4) Easy to arrange.
Different models require different pack shapes to fit and balance the
model. Harnessed packs allow you to choose the optimal arrangement -
front-to-back (inline), side-by-side, or whatever you need.
Be careful!! We see a number of manufacturers offering "2P" or
"3P" packs in long, slim pack formats for large models. We tried
fitting such packs to various models when deciding what formats to make
Hyperion packs in, and found that there are very few models which can
achieve correct CG balance with long packs. So try to mock up the
weight and size of a pack and try it in your model BEFORE you buy.
Harnessing two packs together is easy. You simply choose connectors
appropriate for the target amperage, and wire them up! Here's an
example made for a pair of older low-rate 2200mAh 3S packs, wired in parallel.
The 2200mAh packs were expected to run a max or 22A each, so we have chosen
AC-CONN-35 short 3.5mm gold bullet connectors on the pack side (right).
These are rated for 40A continuous on battery, so are well within spec.
When paralleled to 4400mAh (left side), max continuous current is doubled to
44A, so we are using AC-CONN-4A long 4.0mm gold bullet connectors here,
which are rated for 60A+ continuous. (note: the female 4mm gold connector in the picture on
left is fully insulated with transparent shrink tubing, fyi)
Charging:
We have all heard how dangerous lithium polymer packs can be if charged
incorrectly, and you probably know that a "balanced" pack will provide
better performance, runtime, and service life. As such, we strongly
recommend that Hyperion LVX packs be charged with a combination of Hyperion
EOS charger and Hyperion LBA6 Lithium Balance Adapter.
The EOS 5i and 7i Chargers both require manual setting of cell count "S",
and they also include Smart circuitry to check your settings. In this
way the human and the machine always "double-check" charge voltage for the
other. In our opinion, chargers that rely on either 100% manual or
100% automatic voltage settings are an accident waiting to happen...
The EOS LBA 10 works with almost any charger on the market, and provides two
important functions:
1) It adds an extra layer of charge safety, and it also checks charger
voltage against the pack to be sure they are matched, and will turn off the
charger if a mistake has been made.
2) It insures that at the end of each charge all cells in the pack are
voltage matched and fully charged
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These
new Hyperion VX-Series 20C+ packs deliver the highest voltage and retained capacity in
their class, and in very slim format packs. We are truly impressed by their
performance. We have tested virtually every other cell type on the market, and
have yet to find one that beats the VX in usuable power over many
cycles.