Readers’ battery questions answered
The new AMA Youth Membership program got me thinking: why not sign up my great-grandson? His father, U.S. Air Force Capt. Nick Powers, built and flew a Gentle Lady in the summer of 1993 while staying with us as his father (my son) changed stations. While Capt. Powers flies C-130s, maybe the aviation bug will hit Beck.
Of course, there are the usual distractions that take our potential modelers away from modeling. That is a problem we have failed to successfully address.
Reader Questions
J. Linghorne wrote:
"DeWalt has now started to sell power tools that use Lithium‑Ion cells. The cells that are in the batteries look like the 1100 mAh A123 cells. I phoned DeWalt and tried to get a spec sheet and find out more about the cells. I hoped that they might be of use to me as a modeler. I got nowhere; perhaps you can answer my questions.
- Are the cells subject to thermal runaway?
- What will happen if the cells are accidentally completely discharged? Will they be ruined? Will they catch fire or go into thermal runaway, etc.?
- What will happen if they are accidentally overcharged? Will they be ruined? Will they go into thermal runaway, etc.?
I thought that if they were going to start to phase out the A123 cells that I should buy some more, and so I purchased a new 36‑volt pack. To my horror, I discovered that it did not contain 2300 mAh A123 cells, but 20 1100 mAh A123 cells. In other words, a 2200 mAh pack made up of paralleled 1100 mAh cells. I would suggest that you should tell modelers of this change."
Answer: I have not seen or heard of any instances of A123 cells going into thermal runaway with chargers designed to handle them. I suppose any battery can be forced into thermal runaway if subjected to enough current and voltage.
I have inadvertently discharged several A123 packs and found that they recover nicely on the next charge. They are quite tolerant—much more so than LiPo packs—of overdischarge and of overcharge. If you use a charger designed for A123 technology, overcharge should not occur.
A bit of advice: never stock up on battery packs because they begin to deteriorate as soon as they are manufactured. It's better to buy fresh packs as needed, and the price seems to decrease with time.
Mike Wilson wrote:
"Hi, Red. I always enjoy reading about the latest in battery technology, as well as the history behind where we are. I did find one item in your November article that I don't completely agree with. The line, 'When I watch the frustration of newcomers to the hobby who have been led down the gas- or glow-engine road,' seemed like a slap in the face to that side of the hobby.
I began flying Control Line in the early '60s and glow was all we had. The difficulty, and what I believe to be the main problem for the newcomer, both then and now, is the size of the aircraft they are encouraged to purchase.
Back in those days, Cox was selling small and very unmanageable aircraft to newcomers and they just got frustrated and left the hobby. Today, companies sell larger and better‑flying electric models but they are built so light that they will hardly stand even a slight impact, which is going to happen. The electric systems are just as complex and difficult to figure out as any glow or gas configuration.
My first experience programming the ESC with the stick of my transmitter was a nightmare! I also noticed that the small, unmanageable aircraft are still a prominent part of the offerings and these are mostly, if not completely, of the electric variety.
If I were going to give a newcomer advice on where to begin, I would say go glow or gas and here is why: that will force the person to fly at a site where competent fliers are available to help the novice, and where strict rules of safety are observed. Taking an electric model out to the local park where there is no help available is a formula for disaster. Not only will the novice be frustrated beyond measure, the general public will be at serious risk.
Please don't get me wrong, I enjoy the electric side of the hobby and many of my friends fly them. I just believe that either electric or glow/gas is a good way to get into the hobby as long as there is competent instruction. Both have pros and cons, but the balance is fairly even.
Just an old-timer with a different view."
My reply: Mike makes a good point. Start your flying with a club at which you can get proper instruction and help from experienced modelers. It will make your start in the hobby much easier.
Dick Williams, Flowery Branch, Georgia, wrote:
"Your 'Battery Clinic' article in the September 2011 Model Aviation did not mention soldering leads onto LiPo batteries. Is that what you do and is this a safe operation?"
Answer: No! Never try to solder leads directly to LiPos, but you can on A123 cells if they have tabs. For LiPos, use the leads (power and balancing) that come on the pack.
C Ratings Comments
Dr. J.S. Miller, Professor of Biology, Goshen College, Goshen, Indiana, wrote:
"I read with interest your comments about battery C ratings in the July issue of MA.
I can give an additional, slightly different, reason for preferring higher C batteries. I'm flying a 3‑pound Extreme Flight Vanquish. It flies on a 2200 mAh four‑cell (14.4 volt) LiPo. There's a big difference between a 20C and a 30C battery. Because of its lower resistance, the 30C battery has approximately 50% more useful power and 40–50% longer flight times.
The 20C will give unlimited vertical for about one‑third of a flight; the 30C for perhaps three‑quarters of a flight. The 30C battery gives longer flights. With a 20C battery, I can only use 1200–1300 mAh of the battery's capacity. Beyond that, use of full throttle (as in a touch-and-go) will drag the voltage down below 13.7 volts. The 30C battery will supply 1800–1900 mA of power before it gets pulled below 13.7 volts on full throttle.
I have a Castle Ice Light ESC. As someone mentioned in your article, it's really nice to be able to get out all of that information after a flight. That's how I know how many mAh of capacity was used from a battery at any point in time during a flight. It also reports on a continuous basis mAh of power being drawn at any point in time, LiPo battery voltage at any point in time, ESC temperature, etc.
I also have a Spektrum eight-channel transmitter that has the downlink. One of the things I monitor is LiPo voltage, and an alarm goes off whenever the battery voltage falls to 13.7 volts (3.425 volts per cell). The receiver is set to shut off motor power when the voltage falls to 3.3 volts per cell. I like the downlink because it allows me to use more of the battery's charge without risking a low-voltage motor shutdown.
I don't like to have the motor cut out during a flight. Depending on what I was doing at the moment, it could certainly crash an airplane. With the quiet electric engine, one often doesn't realize that the motor has shut down; the electric motor is too quiet, especially if there are other airplanes in the air."
Hitec Aurora 9
It has been reported that there may be an issue with the algorithm used to determine the remaining capacity shown on the Aurora 9 transmitter display. It can indicate much less than true capacity, causing some to needlessly buy replacement packs.
Always check your pack capacity with any of the many available battery maintenance devices.
New Battery Packs
Herewin has launched its HAIYIN brand of RC LiPo battery packs. I received two 3S 2200 mAh 30C packs to review for my column.
The packs are assembled from cells manufactured in a factory in southern China. The high-quality packs are competitively priced and perform well.
I tested the HAIYIN battery with my Telemaster Electro. After 12 cycles of an AXI 2826-12 turning a 13 x 6.5 APC e-propeller, the maximum current drawn was 30 amps.
After a full-throttle run, nominal 350 watts, the capacity was charted (see Figures 3A and 3B). The pack was only slightly warm after this run. A plot of the performance at the cruise throttle setting — approximately 20 amps — is shown in Figures 3C and 3D.
I ran initial discharge capacity tests (Figure 4A) at rates up to 4C (the maximum my CBA III will handle). After 12 cycles, I discharged to see the individual cell capacity (Figure 4B) and how well the cells remained balanced.
HAIYIN RC LiPo packs
- Voltage: 7.4 volts to 22.2 volts (2S–6S)
- Capacity: 500 mAh to 6000 mAh
- Discharge "C" rate: 20C to 40C
- Pack types: regular, hard case, transmitter, Flightmax, special sizes
For more information about HAIYIN's RC packs, see the company website listed in "Sources."
Avoid Confusion
There are battery packs/cells that carry the "123A" designation. These have been around for some time and are popular camera batteries, but are now being offered in lithium technology for high-powered flashlights. These are not the A123 LiFePO4 batteries we use for powering our models. The 123A SureFire batteries are 3‑volt primary cells and non-rechargeable.
Eye Candy
Ed King built a beautiful rendition of the venerable Lockheed Constellation, "Connie." I somehow lost the information on this model. Hopefully, Ed will see this and share the specifics with us.
Spring Cometh
It's time to give those battery packs a good cycle check for capacity before you launch into the 2012 flying season.
Wrapping Up
This wraps it up for another month. Keep sending those cards and letters. No email connection? Drop me a note at:
The Battery Clinic 12219 NW 9th Ln. Newberry, FL 32669
SOURCES: Herewin Technology Company www.herewin.com
HAIYIN LiPo Batteries [email protected] www.haiyinstore.com
Transcribed from original scans by AI. Minor OCR errors may remain.
