The Battery Clinic - 2011/03 | Model Aviation Library

Author: Red Scholefield

Edition: Model Aviation - 2011/03
Page Numbers: 94,95,96

The Battery Clinic - 2011/03

A half-century of chargers

I'm writing this because I got tired of waiting for someone else to do it.

Early radio-control systems depended on carbon-zinc batteries. Vacuum-tube receivers and transmitters used two batteries: one for filament voltage, usually 6 volts, and one for the "B" high-voltage supply that vacuum tubes required. There were no rechargeable batteries available other than the lead-acid type; these were sometimes used as ground-based transmitter batteries in conjunction with a voltage converter for the higher voltage.

The November–December 1957 Grid Leaks magazine showed circuits for converting a tube receiver to use transistors in place of the temperamental relay. Then transistorized audio sections, and shortly thereafter completely transistorized receivers, appeared. These worked at much lower voltages than the tube versions, so rechargeable packs became viable.

The November–December 1959 Grid Leaks introduced the Eveready Ni-Cd AA battery, while surplus button cells were emerging on the market. These were known as "VO" cells and were sold exclusively through ACE R/C.

Circuits for making your own charger soon appeared. They consisted simply of a current-limiting resistor and bridge rectifier connected directly to a 120-volt AC outlet. These were not for the careless modeler because you were exposed to line voltage anytime you touched the battery pack.

One of the first commercial chargers (May 1960) specifically for the VO and Eveready cell packs was from MC Manufacturing & Sales. It provided a potentiometer that controlled current up to 250 mA; you provided your own 0–500 mA meter.

Radios then appeared with chargers built in. You connected your receiver pack to the transmitter and then plugged the transmitter into an AC outlet. Proline employed such an arrangement.

Our charging needs were soon met by the familiar wall-wart chargers with fixed output for transmitter and receiver batteries. These are still the most common way to charge our system batteries.

Early chargers took many forms and were designed to charge both transmitter and receiver packs at a fixed rate. Readouts were blinking lights, as on the Micropace, or simply an indication of charge status, as on the MEN.

There were specialized chargers for lead-acid field-box batteries as well, which were either wall warts or models such as the ACE CVC. For years ACE chargers fulfilled the need for charging at up to 500 mA rates. The HD500 is good for 500 mA, while the DMVC is 250 mA but can handle two packs independently. If you can pick up one at a swap meet, grab it — it is good for any Ni-Cd or NiMH battery with up to roughly 14 cells.

The need to test packs by discharging was addressed by early clockwork units. They employed a timer that would disengage when the voltage dropped to a preset point and give you a reading of how long the discharge lasted. The discharge rates were preset in the Super Cycle, while you could set them in the Leisure Electronics unit (I had cannibalized this charger for parts, so I'm not sure how it worked). A unit by LR Taylor was similar to the Super Cycle, except that it was calibrated in mAh rather than minutes.

A Charger Ahead of Its Time

The Victor Engineering Super 2 IQ was popular with the RC car set because of its motor-test capability. However, because it was completely user-programmable, it could handle lithium technologies long before they became mainstream. One could set the charge algorithms from a touch pad to suit whatever protocol was required.

I used the Super 2 IQ in my early work with lithium, before any others were available. I removed the motor function and had it reworked for more precise control of the charge currents. It was called the "Industrial" version, because a number of battery-powered-device manufacturers used it for battery selection and testing.

This charger set the bar for all units made since. Unfortunately the manufacturer closed shop to return to Europe to manage the family industrial estate.

Multiport Chargers

Of all the units we have seen, none is more interesting than the Litco Alpha 4. It had the unique ability to charge and discharge four packs independently, but more intriguing was the way it was marketed.

When the Alpha 4 was introduced you could simply order one from the manufacturer/supplier. Once he reached an order level at which he was no longer comfortable, you had to play what became known as the "Litco Lottery." He would open the order window for a few days, and you placed your order there. If you were fast enough, you "won" the privilege of paying a couple hundred dollars for the charger—as long as you were not a resident of Pennsylvania, where sales tax was required. The owner refused to collect sales taxes.

Eventually and without notice, production of the Alpha 4 stopped, and it is no longer available. Hughes RC introduced an alternative in its Spectra 4. It did basically the same thing as the Alpha 4 but also had lithium-charge capabilities.

Sirius makes a four-port charger (with which I have had no experience), but it has limited programming for Ni-Cd and NiMH only. The ElectriFly PolyCharge 4 accommodates only lithium batteries.

Dymond Modelsport has introduced its Super Turbo Quad Charger, which brings Li-Poly balancing to all four ports, as well as offering Ni-Cd, NiMH, and Pb charge/discharge and cycle capability. Dymond also sells a compact 200-watt, 12-volt switch-mode power supply for bench operation.

Preliminary testing of the Super Turbo Quad Charger shows that each channel operates in a manner identical to the Super Turbo II, which I reviewed in the September column. The price is $139, with $55 for the power supply. Hitec also sells a version of this charger.

Four-button units seem to be the chargers du jour; it seems like a new one in this now-familiar format hits the market every day. All seem to have the same general programming. These are good multichemistry chargers and serve most modelers' charging needs.

Computer-Based Chargers

Many units sold today have provisions for connection to your computer to monitor operation, but some can be operated only using a computer. One of the better options is the UBA5 by Vencon.

With its graphical programming interface you can easily design a battery test to do exactly what you want. You can specify the charge method (constant current or constant voltage with peak, timed, or temperature termination) and the charge and discharge currents. You can even use conditional loops in the test.

All voltage, current, and temperature readings are stored in a standard text results file. But the UBA5 is of limited appeal to the aeromodeling community because of its $875 price tag.

Multichemistry Chargers

Many modern units address all battery chemistries that a modeler encounters. One of the more popular options is the ElectriFly Triton series; the latest—the 2EQ—offers either AC or DC input and provides for lithium balancing.

The FMA Direct Cellpro Multi4 is perhaps one of the easier chargers to program. Its computer interface with open architecture lets you create an endless number of charge-maintenance protocols.

Lithium Charger Progress

Lithium batteries brought a new challenge to charger manufacturers. These batteries' needs are completely different from those of Ni-Cd and NiMH.

The first units ignored the fact that lithium packs need to be balanced occasionally and produced poor results and sometimes hazardous situations. The life of unbalanced packs was severely compromised at best, and fires were attributed to their use in the worst cases.

One of the earliest available lithium chargers was the Kokam from FMA Direct. It was followed by the AstroFlight 109, which could miscount the number of cells if a fully charged pack were connected. The FMA Direct Cellpro 4S was one of the first balancing chargers with capabilities extended to cover the new LiFePO4 technology.

High-End Chargers

There is always a quest for the ultimate charger—one that will make everyone happy. Of course that is impossible to attain.

The Tejera Microsystems Engineering Xtrema is an example of design creativity. Although it is limited to lithium technology, it is unique in that it includes a watt-meter function. There are numerous accessories that can enhance the capabilities of the Xtrema.

The Cellpro Power Lab 8 from FMA Direct is touted to support all current and future battery chemistries. The 1,344-watt unit offers high-power charge and discharge capabilities. It features a computer interface as well, enabling the aeromodeler to log and graph all major operations when using the free charge-control software.

I have only scratched the surface; literally hundreds of chargers have been offered to our hobby. Some have been excellent, such as the Shultz and Orbit. To cover more would require a large book and more time than I would want to dedicate to such an endeavor.

Spring is on its way. Make sure that you have that winter project checked over well before your first flight. It might be better to limber up on something familiar.