Q: How does Nicad or NiMH useable pack capacity compare to A123's? Same flight time for the
same capacity?
-
The example plane here is a 1/4 scale warbird equipped originally with
a single Sanyo 2400ma 5 cell NiCad pack. Load testing between flights, I’d get 4 flights before the ESV at 1 amp would
display under 6v, indicating ‘recharge’ time. Cycling the pack at that point revealed the same amount of ma consumed
on average… but that was it for flying the pack. In essence, the NiCad gives up a bit more than half it’s rated
capacity before I got to a required recharge point.. the LiFe would go much further.. if it had to. The Nicad wouldn’t.
Net effect is seamless to me though.. either way, I was recharging after 4 flights… but carrying significantly
more ‘reserve’ useable capacity with the LiFe pack.It must also be mentioned that both Nicad and NiMH INCREASE
impedance as they discharge.. the LiFe pack did not.. another significant bonus.
*
Q: Can I use my ‘XYZ’
brand NiCad /NiMH charger or Wall Wart on LiFe?
*
No. Let me be specific… HELL NO! Here’s what’s going on.. LiFe’s nominal
voltage per cell is 3.3v. While the charge routine is similar to LiIon or LiPoly, the max allowable voltage under charge is
lower than any other Lithium technology cell, usually about 3.6v; so using a standard LiIon or LiPoly charger will do damage.
For you NiCad - NiMH guys, the entire charge sub-routine is different . As of now, there are a number of LiFe capable
superchargers coming into the marketplace.. these will deal with ‘em as well as the various other types of Lithium and
NiCad/NiMH packs but assume my first answer of HELL NO applies until you review your chargers manual. If you not sure, contact
the charger mfg or distributor. Don’t let ‘em blow smoke up your backside either. Get it in writing if it’s
not called out in the manual.
*
Q: What in heck is the 'Cell Balancer' function all about?
*
Simply put, this monitors voltage of the individual cells and keeps them closely matched or ‘balanced’
in voltage during the charge routine.. Some A123 enthusiasts (and charger MFG's) will try and convince you that A123
packs don’t 'require' balancing. This claim is bunk for those of us that value what we fly... Unbalanced charging may
be adequate for a tool pack or a ground application, however the reality of field trials with a wide variety of non-balancing
LiFe capable chargers has demonstrated that balance charging is the best way to avoid damage to the pack and reduce risk for
the aircraft. Balancing= Good for the pack, good for the plane. See the A123 Setup Guide for how to easily accommodate balance charging at the field.
*
Q: My A123 pack has 2 connectors.. which do I charge
thru?
*
The
light gauge wire and connector is the 'cell tap' or 'node' connection.. The heavy gauge wire is the standard pack
'feed' that connects to the switch harness. Don't attempt to hook the 'cell tap' lead to anything BUT the node or celltap
port of a balancing charger. This connection is used by balancing chargers that require a seperate three wire connection to
the charger in addition to the two wire pack feed to accomplish a balance charge. If your not balance charging, or are charging
at high rates, charging should be done on the standard pack feeds as with NiCad and NiMH packs.
*
Q: I have an FMA
Charger .. it charges ONLY through a 'node connector'.. do you have an adapter for your 'standard univ' cell tap?
*
Yep.. and I've also made available as a no
charge option for the celltap on 2 cell packs the FMA Node Connector. Most folks still wind up ordering the pack with
the Univ cell tap and building their own 'extension' or ordering our FMA Node to Univ Cell tap Adapter to make it a bit easier
to access the pack for charging via a 'ernst' charge port on the side of the plane. See notes below on how to make an extension
from the univ celltap to any brand chargers balance port.
*
Q: I need to make an adapter cable for my 'Brand X' balancing charger for your 'Univ' cell tap.
What are the color codes on your univ tap plug?
*
The 22g univ tap connector on our two cell packs is very easy to build an adapter for. Using an aileron extension
to make an extension/adapter cord is a snap for any charger.. Just snip off the 'male' servo end from the aileron extension
and solder a 'pack side' plug that mates with your chargers balance port.. red is pack positive, black (or brown) is pack
negative and the white (or yellow) lead is 'node 1' on your balance plug. Another way to explain what that white or yellow
lead is relative to the red and black.. it's the 'negative' for the red lead, or the 'positive' for the black lead, allowing
the charger to 'see' the individual cell voltage during the charge.
*
Q: Do I need to ‘balance’ the pack every charge?
*
The only way to avoid costly and aggravating fried battery packs is by using a balance charger EVERY TIME.. Here's
the prime issue: A close to fully charged pack, deeply discharged pack or out of balance pack may be easily mis-identified
by a 'smart' charger WITH THE WRONG CELL COUNT. The results are usually always a ruined pack. If a quality balancing
charger is used and correctly connected, the charger will see the individual cell voltages in the pack, correctly identify
it's cell count and usually report on the individual cell voltages all the way through the charge routine. Virtually every
pack failure I've seen to date relates back to a 'smart' charger incorrectly identifying the cell count or state of charge
of the pack.. with a wiped out pack (at the minimum) being the end result. I Use the FMA Multi-4 and like it's ability to
balance charge with just a single 3 wire connection between the pack and the charger.. it reports on individual cell voltages,
provides a 'percent of charge' report on the pack at the start of the charge and reports on individual cell voltages at the
end of the charge. Knowing and observing individual cell voltages at the start and end of the charge is the only SURE way
to determine relative charge state and condition for the pack.
*
*
Q: What changes do I need to make to charge these in the plane? I’m using HD JR switches.. do I
need new ones?
*
Nope.. no new switches required. Two approaches
to use here depending on the type of charger you are using. Most balancing chargers use two connections to the pack;
a three wire 'balance tap' lead as well as the power feed. Some balance chargers, like FMA's Multi-4, will balance charge
with just one connection to the charger. EyebalI the Setup Guide to determine how to take advantage of the simpler 'single 3 wire combo' set up if you have an FMA charger. If your
charger requires the dual connection setup, you'll order the pack with a seperate balance tap and seperate power feed. Since
virtually every ‘balancer’ equipped charger out there uses a different oddball plug to connect the balance tap
to the charger I standardized the packs tap to the industry standard universal servo connector for the balance tap lead. To
connect to the universal balance tap on the pack all you need is an aileron extension with the plug that fits your charger
balance port spliced onto the other end. Now, if you balance charge during setup before the first flight of the day,
no extra stuff need be added to the plane.. hook the chargers accessory balance lead to the pack tap. The ‘bonus’
part with the ‘standardized’ tap on the pack pops up when you decide to balance charge in the plane with your
two-connection charger.. all you need is a ‘ernst’ type chargeport in some convenient spot on the plane and a
standard aileron extension from that to the battery balance tap connector... and then you can use the same cable you used
to connect directy to the packs tap to plug into the 'ernst' chargeport to connect to the charger. I like simple. A LOT.
*
Q: These are Lithium’s.. don’t lithium’s need a Voltage Regulator for use as a an Rx
pack?
*
Once more for you folks out there with LiPoly
or LiIon systems.. no regulator is required for modern Rx’s and Servos with these A123 LiFe 2 cell packs... because
these packs at full charge and under load are operating at about 6.6v.. the same voltage level as a fully charged and loaded
5 cell 6v NiCad pack. If you have the latest generation 2.4 radio system and digital servo’s rated at 6v and your system
exhibits twitching or instability on an A123 2 cell pack then something is wrong with your Rx or Servos.I’ve
had folks with 5 cell Nicad packs complain about twitch and jitter with some recent Hitec servos.. these were replaced by
Hitec, problem solved. Folks, if your running some dinosaur Rx or antique servos, all bets are off; proceed assuming you’ll
be using 4 cell NiCad packs until you upgrade your radio gear. However, if your running anybodys 2.4 Rx system and modern
digital servos rated for 6v operation you’ll find the A123’s operate the system perfectly. Rule of
thumb, if your running 5 cell 6v Rx packs without regulators, your good to go with A123’s and no regulators.Note:
If you’re a Heli pilot with a gyro that won’t operate with a 6v Rx pack, then your outta luck too.
*
Q: I’ve got a DA Engine.. can I use this as an Ignition pack?
*
Yup.. according to DA there are no issues with LiFe packs with their ignition modules. Again, no regulator required.
If you’ve got something other than a DA engine with a different ignition module, you’ll need to check with that
mfg or distributor; but again, as a rule of thumb, if you’ve had no difficulties running a 5 cell NiCad or NiMH pack
on your ignition without a regulator then the A123’s should do just fine. Remember the loaded voltage of LiFe ignition
pack is 6.6v.. the same as a fresh NiCad 5 cell pack.
*
Q:
How about use for Turbine ECU’s?
*
Since a 2 cell
LiFe’s nominal operating voltage under load is @ 6.6v attempting to use them as a drop in replacement can (and likely
will) lead to flamer starts and lousy throttle controllability response. We've made available 3 and 4 cell liFe Turbine packs
for those folks that need higher voltge for the ECU, as always, check with the ECU/Turbine MFG or Distributor for the
required input voltage for their device.
*
Q: I read somewhere that A123 LiFe cells can be charged at up to 10 amps.. does that make sense?
*
Yup.. that’s correct. According to A123’s specs.. 10 amps. Of course, here’s where a brain on the
part of the end user comes into play. What are your connectors and switches rated for? If your like me and use HD system switches
and industry standard battery and servo connections, then you’d better cut the charge rate down to what those connectors
can handle.. 3-4 amps. Tops. If your using direct connections from the pack to the charger via 18g wire and Deans or Anderson
connectors, then you can use the 10a charge rate if your charger will go that high. For most of us, the 3 amp rate through
the HD switch ports makes sense, and the difference in time (15 min vs 3 minutes for a normal battery refueling at ½
discharge) is of no consequence.
*
Q: I've got a 25% Sized Yak with a
DA 50, all digitals and I fly the pants off it.. what A123 LiFe setup would you recommend?
*
Keeping things light is always important.. and in the 25% birds, battery system weights have a bigger percentage of
total weight impact than in the larger birds. In your situation a minimum setup would be a single 2300 A123 LiFe pack
with dual leads and feeding dual switches. For the Ignition, a single 1100 A123 LiFe pack and with this setup, you'll likely
get 3-4 flat out flights between charges at least.. maybe more. See the notes above about how to find out how many flights
you can get with your bird the way you fly it.
*
Q:
I’m Running two 2400 Nicad 5 cell packs with dual switches in my 40% Extra.. DA-150 up front. What will I need to upgrade
to A123’s?
*
An A123 Charger, a charger cable to connect to
your pack or switch, a balancer cable, a servo extension to make your balancer cable out of and a pair of A123 two
cell 6.6v 2300 packs. You MIGHT want to pick up a pair of 'ernst' type charge ports for the side of the plane to use the balancer
for on-board charging if you don't have the FMA Cellpro or Multi-4 charger.. Note that your CG may change.. this dual pack
A123 system will weigh approximately HALF of what the two 5 cell pack NiCad system weighed. For the ignition.. one more as
above.. it'll probably run the engine all day.
*
Q:
Same Question, same size bird, but I have a single 4500 NiMH 5 cell pack with dual leads & switches and
I don't want to lose flying time with the 2300 LiFe's.
*
Same
answer as above.. use a Dual 2300 LiFe pack setup with your two switches. You won't lose a bit of flying time.. in fact, you'll
probably gain a flight or two and will have improved the dependability a bit to boot without adding a bit of weight.
*
Q: Do I have to buy a new charger?
*
Yes.. Normally.
Unless your charger is A123 compatible. There’s a work-around available called the ‘dapter’ to allow safe
charging of A123 cells with a NiCad/NiMH charger.. do a quick internet search for this device to see if it fits your needs
and will work with your current charger. The feature that I like to see most on a charger used for A123 support is the balance
feature.. while there’s likely to be ongoing debate on the need for balancing A123’s with every charge there is
at this time no doubt that running a balance charger will prevent charger mishaps that result in fried packs.
*
Q: Do I need to disconnect the switches from the Rx if charging two packs at the same time like I did
with my NiCads and NiMH parallel setups?
*
Ahh... the insidious
'common ground issue'. Yup; chances are; unless your charging through a power box designed to eliminate this issue, then you'll
need to unplug one of the switches to eliminate the common ground.
*
Q:
I have a standard A123 Charger that won’t ‘cycle’ or discharge. Can I use my programmable NiCad/NiMH charger/cycler
(Triton, Triton II, Multiplex LN5014, Accucycle Elite, etc) to discharge them and get capacity numbers for evaluation and
testing?
*
Yes.. IF you can set the voltage cutoff on discharge
and discharge load, no problem. (most cyclers are programable for low voltage cutoff in the Nicad or NiMH menu's) Again..
this is for cycling for formation or evaluation.. not for charging. The discharge rate should be 1amp, the voltage
cutoff should be 2v per cell. See your charger/cyclers manual for how to effect these changes and use an A123 LiFe Compatible
Charger to charge A123 LiFe packs.
*
Q:
What Charger do you recommend?
*
Lordy..
well; there's an awful lot of chargers out there that'll handle LiFe now.. FMA's Cellpro and Multi-4 are my personal favorites
since they accommodate balance charging with just one three wire connection to the pack and with a simple adapter can balance
charge, check individual cell voltages and produce a reliable reading on the percentage of charge in the pack right
through the switch chargeport. There's a fair number of charger reviews on RCU and plenty of opinions
out there.. in my experience, if a pack can be easily checked and balance charged via the switch chargeport, the chance of
a pack or charger issue ruining your day are reduced by a potentially dramatic degree. See our Setup Guide for a charger discussion and various setups.
*
Q: Do I need to Formation Charge A123
LiFe packs?
*
Yes.. but in this situation and with these cells
the concept of ‘slow’ charge and ‘fast charge’ no longer have the meaning we associate with NiMH and
NiCads. The normal formation routine would be WITH the balancer feature in use and the charge rate should be 2 to 3 amps maximum.
Use a discharge current of 1 amp, and a discharge cutoff voltage value of 2v per cell. I run 3 charge/discharge routines..
but have had folks tell me no more than one is required. I smile and say “That’s nice.. how much time and money
do you have invested in your plane?” Folks, I’m a cautious
old codger, and I’ll likely go to the grave that way.. without ever losing a bird to an underperforming battery that
was hurried through a break-in process. These are chemical engines.. THAT part of this technology
is no different than any other.
*
Q: What Field Charge rate do you use?
*
I normally field charge at 3 amps.. but that’s the limit of my switches and connectors. When I field charge with
the balancer on the first charge of the day, it’s at 2 amps. How you set up and charge is really limited by the connectors
and wiring and the charger capabilities. One work-around to speed up charge time with chargers that work at higher rates is
to charge the pack directly.. not through the standard system connectors on most chargeport switches. Install an Anderson
or Deans connector on the switch input side, order the pack with Anderson or Deans plugs to match and disconnect the
pack from the switch and charge through the pack feed.
*
Q:
My NiMH packs are often pretty low after just a couple of days of sitting. Will these (LiFe) hold their charge better?
*
Yup. Lots better. And better than NiCad’s, too. The rapid
self discharge characteristic present in low impedance Nicads and NiMH cells is just not present with LiFe cells. BUT.. (there’s
always a ‘but’.. you notice?) we are in a brave new world or radio gear and systems applications. In an awful
lot of equipment out there I’m finding system loading present at the pack even with the system ‘off’. On
some of the 2.4 systems and most ECU’s and some ignition modules there’s a constant current draw of 2-4 milliamps..
so, leaving packs plugged into the switches for weeks or months at a time can cause grief and surprises. I don’t like
grief and surprises. I unplug my packs from the switches when I’m done flying. I strongly recommend you do the same.
Get in the habit, just do it.
*
Q: How should I store A123 packs?
*
My preferred method is to balance charge and cycle, record the capacity info, then balance charge again and disconnect
them from all devices. What these cells DON’T like is discharge to 0 volts under a load and they don’t like sub
zero weather conditions. Since they have a very low self discharge characteristic there’s no risk of finding a zero
voltage pack in the spring after a winter layup. If you keep your plane in an unheated environment and suffer with sub-zero
conditions where the plane is, it would be prudent to take the packs out of the plane and bring them in where you are. Like
most batteries, they like the same temperatures you like.
*
Q:
What happens when the plane gets hot? My NiMH packs suffer on hot days, I notice lower voltage and capacity. Same when it’s
real cold out.
*
Another thing I like about the LiFe’s is
the thermal increase performance… these cells are more resilient than any other battery type to temp build-up inside
the application it’s powering. A123’s specs indicate routine operating temps as high as 140 degrees with only
a 12% drop in capacity. So, if your big bird has a lot of canopy glass cooking your NiMH packs down quickly, LiFe will be
a pleasant improvement for you. On the other end of the scale, once the outside temps drop to 4 degrees below zero F
we see about 20% loss of capacity. Just in case you like to fly in Alaska in the winter, take a flight or two less than in
the summer.
*
Q: Can I get custom electric flight packs from you built
out of A123’s?
*
Not without using a gun. I worked for a guy that
was a pretty smart feller once.. he used to love to say ‘Just because you can do something, doesn’t mean you should’.
Over the course of the last 5 years I’ve had a lot of folks tell me ‘I’m missing the boat’ with electrics
and electric flight. Gent’s, I built that boat… back when we used to tear down Drill Motors for gearboxes
and measure current draw by the amount of smoke coming out the back on the climb out. I have a wall full of trophies and fond
memories of the days when ingenuity in electric powered modeling and pilot skill made a bigger difference than the amount
of money thrown at the challenge.
-
My current joy in the hobby is The Big Birds..
it’s what I fly when I finally get out to enjoy a day as a modeler. This is my retirement, and what I do is a labor
of love.. not a driving grind to rake in the bucks and fleece folks. So, there's no big shop, no leveraged inventory, no staff
to supervise, no national ad campaigns, no smoke and mirrors and 'man behind the curtain' crap. It’s just
me and my many decades of experience in this narrow field, and that’s the way I like it. Since I'm still working
despite the crushed economy, I guess it's how my customers like it too. The amount of work that comes in here from the commercial/military
RPV end and the folks flying Giant Scale and IMAC keep me more than busy enough to pay the bills; they are, by the nature
of what they are doing and the level of investment in time, effort and craftsmanship they do it with; competent
modelers and pilots... and they keep food on the table without driving me batty with ‘is the red wire important’
questions. So, no.. I’ll not be building packs for the electric flight folks in our fine hobby any time soon. Don’t
ask, and I promise not to promptly skin you alive and feed the cat with your entrails. J
s
Steve Anthony
NoBS Batteries
/ Hangtimes Hobbies
October 2008, updated May 2010
email: hangtimes@optonline.net
