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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 6 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. 
