IT’S THE second
anniversary of “The
Battery Clinic.” Just
how much can you
write about batteries
and chargers? That
question went
through my head
two years ago, but
from the E-mails I
get it seems that
there is a
knowledge leak somewhere; the more that I try to pump in, there
never seems to be an overflow.
I RECEIVED the following sad story from a reader.
“I just lost a beautiful 60-inch-span S.E.5a WW I fighter to
possible receiver battery failure. I’m using a JR XP8103dt FM,
digital 811 servos (five), with a 600 mAh receiver pack. I flew for
about 1.5 hours that fateful day when it hit Mother Earth.”
You are flying way too much airplane for a 600 mAh pack. Your
problem is kind of like blaming the gasoline when you run out of
gas.
One should have a good idea of how much his or her airplane is
drawing in flight. This is not difficult to determine. Complete details
are presented at the Battery Clinic at www.rcbatteryclinic.com.
An excerpt from that article charges you to know what your
system consumes in the way of energy per minute of flight. You can
figure this by charging a pack and then discharging it on a cycler to
determine how much capacity it has—fully charged. Then recharge
and go fly.
Record your system on time and immediately discharge the pack
when you return home. This will tell you how much capacity you
have left.
Let’s say you fly for 40 minutes and get 390 mAh when you
discharge the pack. From the initial discharge from a fully charged
pack you got 585 mAh.
That means you discharged 195 mAh in the 40 minutes you flew,
or approximately 5 mAh/minute. From this you know your pack is
good for 116 minutes of flight time under the actual flight loads.
You don’t want to take it this close, so give yourself (and your
model) a margin of safety: 25%. That would set your safe flight time
to 75% of 116 minutes, or one hour, 27 minutes.
You should do this for each airplane. You should also do it for
your transmitter at least once to accurately characterize its “flight
time.” The system usage will vary depending on your flying style,
airplane size, and number of servos used.
If you have no means of checking battery capacity, you are
essentially flying in the dark. I recommend as a minimum an ESV
(Expanded Scale Voltmeter) so you can check the pack before each
flight to see how it is holding up.
As for packs themselves, any Sanyo brand, which a number of
suppliers provide, is as good as you can get in quality. You should
have a minimum of 1200 mAh for your setup.
One way to achieve that is by running a dual-pack setup, also
explained in detail at The Battery Clinic. This way you can use your
present 600 mAh packs and the wall-wart chargers that come with
your radio.
Otherwise you will have to get a charger that is capable of
handling the large-capacity packs. Although there are numerous
How to determine if you are flying too much airplane on a given battery
July 2007 97
The Battery Clinic Red Scholefield | [email protected]
Also included in this column:
• Adapter question answered
• Transmitter charging station
• Bantam BC6 multichemistry
charger/cycler
The JWT connector mates with the transmitter plug. • Adapter tricks
The transmitter charging station in the author’s shop.
The Bantam BC-6, with adapters, can be run with AC or DC
power.
07sig4.QXD 5/23/07 9:34 AM Page 97
good systems on the market, several modelers have proven Great
Planes’ Triton to be an extremely capable unit.
Another reader wrote:
“I have been away for a while. I thought that I had mentioned the
type of radio I had. It’s a JR X378 radio that holds the small tiny
white female plug at the end. How do I connect to the battery pack
when it is moved outside of the transmitter?”
Make a male plug to match the white female plug. I use a small
piece of 1/8 plywood and push two straight pins through it to match
the spacing on the transmitter plug, solder wires to this, protect it
with heat-shrink tubing, then connect the other end to a socket that
matches my transmitter charger plug (available at RadioShack) or
the particular charger I plan on using.
Another approach is to acquire a JWT male plug (used in park
flyer setups). This matches the transmitter plug perfectly.
Transmitter Charging Station: It seems like there is more wall
space than bench space in our shops. I know a handy way to keep
your transmitters stored and ready for use.
I have found the 700 mAh packs that
come with the transmitters more than
adequate for my flying sessions. On the rare
occasion I need more, I take an extra
charged pack or any one of the small,
programmable chargers presently available
and give the pack a fast charge at the field
between flights.
Wood blocks are glued to a piece of
paneling to hold the transmitters. Wall warts
are plugged into a power strip, which is
plugged into a TME CHARGEminder that
is programmed for a fixed charge time and
then automatically goes into a pulsesustaining
charge mode.
Bantam BC6: I get lots of requests for a
multichemistry charger/cycler that can be
operated from either a 120-volt AC line or a
12-volt source. Bantam must have been
listening when it introduced the BC6 that
can be operated in your shop with AC or at
the field with DC power.
98 MODEL AVIATION
It can accept three types of Lithium batteries: Li-Ion, Li-Poly,
and LiFe (A123), as well as Ni-Cd, Lead-Acid, and NiMH
chemistries. The BC6’s specifications are as follows.
• Operating voltage range: DC 11-18 volts, AC 100-240, 50/60
Hz
• Circuit power: Max 50 watts charging, max 5 watts discharging
• Charge current range: 0.1-5.0 amps
• Discharge current range: 0.1-1.0 amps
• Current for balancing: 300 mA/cell; Ni-Cd/NiMH cells: 115
• Lithium cells: One to six
• Weight: 20.5 ounces
• Dimensions: 5.5 x 5.1 x 1.8 inches
The unit has an individual-cell-voltage balancer built in so it
does not need an external balancer when charging Lithium
batteries for cell balancing. It can also monitor and balance
individual cells during the discharge process. If the voltage of
any one cell varies abnormally, the process will be stopped with
an error message.
Fast-charge capability reduces Lithium batteries’ charging
time, and storage mode sets the final battery voltage at a suitable
level for long-term storage (several months or longer). The packs
should periodically be submitted to the storage charge to assure
that their voltages have not dropped to a level that is detrimental
to the pack.
Each of the five data memories can be recalled anytime you
need without reprogramming. Perform one to five cycles of
charge>discharge or discharge>charge for battery-performance
confirmation.
For the advanced user the BC6 offers an optional PC-based
program that shows a graph of voltage, current, capacity, and
temperature curves. It also shows the individual voltage of each
cell in the Lithium battery pack.
Connection to the computer is via USB port. The unit is
housed in an aluminum case that provides for efficient cooling.
Adapters are available for most popular battery systems
including Align, Dualsky, ElectriFly, E-flite, Poly-Quest,
Hyperion, E-Tec, MaxAmps, Kokam, and Thunder Power. Also
supplied is an adapter-plug pigtail to make your own, as I did for
a Cellpro 4S pack to the BC6. (Shown below the charger.) You
can review the manual at www.bantamtek.com/Manual/BC6%
20English.pdf.
I found an interesting aspect of this charger. The 12-volt input
cable is hot; it has 12 volts on it when the unit is connected to an
AC outlet. If these are shorted together the unit shuts down. The
good news is that you can use this as a 12-volt supply to run
Removing the pin from the balance connector.
Make a parallel connection adapter. Text has details.
07sig4.QXD 5/23/07 9:35 AM Page 98
another charger at the same time you are
using the BC6.
The amount of current available is
limited but ample for most chargers/
cyclers. I cut the 12-volt source leads
approximately 4 inches from the unit (see
photo), soldered on 5/32 brass tubing,
covered with heat-shrink tubing, and can
now plug in another charger or leads with
alligator clips when needed and not have a
long cord cluttering up the bench when it is
plugged into AC.
The BC6 testing sample was provided
by RC Accessory, Inc., 3304 Foxridge Cir.,
Tampa FL 33618; Tel.: (813) 765-0124; Email:
[email protected].
Adapter Tricks: J. David Johnson from the
RCGroups “Batteries and Chargers” forum
submitted the following information.
“It took a little while to find this info so
I thought I’d share it. I have the Cellpro 4S
charger with the Thunder Power/Poly-Quest
multi adapter card ... I can attach a 3S FP
EVO into the TP port for 3S, and it charges
fine ... But when you attach a 4S FP EVO
to the TP 4S port, the red light comes on
indicating a reverse polarity error. It does
appear to go ahead and charge with no issue
... but the light is unsettling.
“There is not a real polarity problem ...
but the EVO 4S packs (and possibly newer
Thunder Power packs) have both the five
and six pin connected and only the fifth pin
is needed ... it seems that if the sixth pin is
connected ... the Cellpro adapter board
reads it as a polarity problem ... ”
Since I’ll only be using the Cellpro 4S
charger (I love this thing), I decided to
disconnect the sixth pin. You can remove it
from the connector by lifting the little tab
on the last red wire at the end of the
connector and backing out the wire. Cover
the bare pin with heat shrink and slip it
back into the battery pack beside the power
lead.
Do you want to run two packs in parallel
for longer flight time?
1) Epoxy two male Deans Ultra Plugs
together.
2) Solder the positive pin of the female
Deans between two pins on the male Deans.
3) Solder a short piece of copper wire
between the three negative pins.
4) Cover with shrink sleeve.
This makes a compact parallel connector
setup.
It is the peak of the flying season here in
the swamp. I have models to prep, batteries
to charge, and flying to do. I hope to have
new battery/charger goodies to tell you
about after my trip to the Toledo Weak
Signals Expo.
I’m still at 12219 NW 9th Ln., Newberry
FL 32669, and my computer still