The Battery Clinic
Red Scholefield | [email protected]
Is a two-cell Lithium battery too much for your receiver/servos?
Hobbico is selling LiFe Source 6.6-volt, 1100 mAh 10C receiver battery packs. This Lithium-Iron-Phosphate (LiFePO4) technology yields a lightweight, high-energy, high-density battery with more power than Ni-Cd or NiMH receiver batteries.
It is claimed that no regulators are required. While LiFe Source packs have a nominal voltage of 6.6 volts, they can be as high as 7.2 volts immediately off a charge.
Most manufacturers are okay with 6.0 volts for airborne packs. Futaba advises against this higher voltage. Is that company merely being conservative? I don't know about other manufacturers.
Hard, fast numbers are difficult to pin down in these cases, and higher voltage is generally more stressful for electronics designed for a specific voltage. So how much is too much? I sought the advice of Tony Stillman of Radio South, and following is his reply:
"I am a little concerned as well, but many people have used this LiFePO4 chemistry without any regulators. I know that some servos don't like 6 volts, so they should not be used with these packs. The receivers should handle the voltage without problem."
(Editor's note: Using the LiFe packs from Hobbico has been a success so far in 30- to 90-size helicopters and aerobatic models.)
Staying Charged for Years
You might have been going to the same RC meets for years, but have you noticed that one person who always seems to be there to hold down the frequency impound? At the On Top of the World RC Flyers events in Ocala, Florida, that is Adella Sherman. She is the wife of club member Sid Sherman (who was a World War II PBY crewman).
I asked Adella how long she has been handling impound duties. She replied that she offered her services for Orville and Wilbur at that little meet they had at Kitty Hawk, North Carolina, but that they didn't need it.
Adella is the kind of person who makes this hobby what it is: fun! Everyone should be particularly nice to the impound lady.
Dymond Modelsport Super Turbo II Charger
The first thing you might notice when you unpack the new Dymond Modelsport Super Turbo II charger is the unusual finish on the case. The carbon-fiber look sets it apart from many other units at the field. I asked Dymond Modelsport what the material is; they replied:
"The design of the housing can be called Carbon Look plastic. The same technique is used by Graupner and some other manufacturers for electronic devices like chargers, amplifiers or phone housings."
The configuration of the Super Turbo II is basically standard for today's four-button chargers. Identification on the programming buttons is molded into the case and can be difficult to read from certain angles, but the layout is familiar and intuitive. Connections are on the right-side panel, where they do not clutter the working face of the charger.
Versions and physical features:
- Sold in two versions: 12-volt DC only, and 110-220V AC/DC.
- The AC cord plugs into the charger so you don't have to carry it to the field.
- The DC power cord uses a regular removable plug (similar to transmitter chargers), so it can be removed and not congest your charging bench.
- The housing has a carbon-look finish.
Adapters and connectors:
- Four adapter boards are available (you can specify which ones when ordering) to accommodate nearly any balancing connector (except the FMA Direct Revolectrix).
- The charger provides an "octopus" with seven power connectors, including transmitter, receiver, glow driver, Deans Ultra, and GWS.
Manual and functions:
- A pocket-size, 15-page instruction book (clear English) covers operation and includes a Program Flow Chart for Li-Poly, LiFe (A123), Li-Ion, Ni-Cd, NiMH, and Lead-Acid batteries.
- Modes include fast charge, balance, storage, and cycle charge options. Warnings and error messages are listed.
- Includes a storage function for lithium-based batteries and a modest discharge capability (up to 1 amp).
- Charge rates up to 5 amps (or 75 watts) can be programmed into any of the five memory slots.
- Choice between balance charging or not for lithium packs.
- Allows cycling packs up to three times to check or confirm capacity.
Performance and specs:
- 0.1- to 5.0-amp charge capacity.
- Accommodates:
- 1- to 6-cell Li-Poly packs,
- 1- to 15-cell Ni-Cd or NiMH packs,
- 1- to 10-cell Lead Acid packs.
- Cutoff sensitivity (for Ni-Cd) selectable from 5 to 20 millivolts per cell.
- Charging behavior for Li-Poly shows current tapering as cell voltage approaches the per-cell limit (e.g., 4.2 V per cell).
Accessories and price:
- Charger comes with one balancing board suited to the 1- to 6-cell connector of your choice; three additional boards available. Full set of four balancing boards costs $15.
- List price: $149.95. Discounted on the Dymond Modelsport website to $79.99 plus shipping and handling. DC-only version: $59.99 plus shipping and handling.
The compact Super Turbo II has the features necessary to maintain the health of common hobby battery packs and is an excellent value, especially if you already have DC available at your charging bench.
First-Class Charging Station
Following is a piece that Walt Thyng posted on an online forum describing his club's charging setup:
"This is what the Fox Valley Aero Club in St. Charles, Ill. (my club) did.
"The 'Juice Bar' (my wife came up with the name and it stuck) comprises nine charging stations powered by three Iota DLS 55 power supplies. The 12V lugs are 3/8" threaded brass tubing with a 3.2mm hole for banana plugs. This covers just about any type of charger power lead requirements.
"Because there are some flyers with special needs, each station has 110V AC as well. Each group of three stations has its own power supply and on/off switch so that we don't have to run the whole system all the time. The entire system is controlled by a master timer which turns it on and off at the beginning and end of the day."
Vaporware Department
Here are a couple of items to ponder from recent tech coverage.
Flexible energy-harvesting sheets (MIT Technology Review) "Material could charge portable electronics with every step. Researchers at Princeton University have created a flexible material that produces record amounts of energy when stressed.
"The researchers say the material could be incorporated into the soles of shoes to power portable electronics, or even placed on a heart patient's lungs to recharge a pacemaker as he/she breathes."
Maybe you can use your imagination to apply that to aeromodeling.
Lithium-air batteries (Gizmag, Darren Quick) "Lithium-air battery technology looks to have a big future. With the potential of providing energy densities up to three times that of conventional lithium-ion batteries, many companies, including IBM and General Motors, are pursuing work on lithium-air batteries.
"Researchers at MIT have made a breakthrough that could help make the commercial development of lightweight rechargeable batteries a reality. Unfortunately, lithium-air batteries haven't become a commercial reality because there has been a lack of understanding of what kinds of electrode materials could promote the electrochemical reactions that take place in these batteries.
"The MIT team admits there are still a number of issues that need to be addressed before lithium-air batteries become a practical commercial product. The biggest issue is developing a system that retains its power through a sufficient number of charging and discharging cycles to be useful in vehicles or electronic devices.
"Researchers also need to investigate the chemistry of the charging and discharging processes, to see what compounds are produced and where, and how they react with other compounds in the system.
"While some companies working on lithium-air batteries have said they see it as a 10-year development program, [MIT associate professor Shao-Horn] says it is too early to predict how long it may take to reach commercialization. 'It's a very promising area, but there are many science and engineering challenges to be overcome,' she says. 'If it truly demonstrates two to three times the energy density of today's lithium-ion batteries, the likely first applications will be in portable electronics such as computers and cell phones, and only later would it be applied to vehicles once the costs are reduced.'"
Solar Impulse first flight (Gizmag) Also covered on Gizmag.com, the Solar Impulse HB-SIA flew for the first time over Payerne, Switzerland. The solar-powered, man-carrying craft reached 4,000 feet and performed control-system maneuvers. It was airborne for 87 minutes before landing safely.
"With the wingspan of a Boeing 747 and the weight of a car, never before has an airplane as large and light as the Solar Impulse flown before. It lifted off at a speed no faster than 45 km/h and, once airborne, completed a series of turns by gently tilting its wings that measure 63 meters (208 feet) from tip to tip."
I think that one will work for us—at least here in the Sunshine State. —MA
Sources
- Hobbico
(217) 398-8970 www.hobbico.com
- Dymond Modelsport
(858) 220-4004 www.rc-dymond.com
- Gizmag.com
- The Battery Clinic
12219 NW 9th Ln. Newberry FL 32669 www.hangtimes.com/redsbatteryclinic.html
Transcribed from original scans by AI. Minor OCR errors may remain.
