Ni-Cd the Topper
AN EASY-TO-BUILD PROJECT THAT CAN TRICKLE-CHARGE AS MANY AS TEN BATTERY PACKS SIMULTANEOUSLY
In electric flying there are a number of simple tricks that can really make a difference in performance. One of these is to charge the Ni-Cd pack until it peaks (or gets warm) on the fast charger, and then put it on trickle charge overnight before you go flying.
One charger works well to quick-charge several packs, but how do you trickle charge multiple packs for a day's flying? You build the Ni-Cd Topper, a multiple-output trickle charger. By simply adding components, as many as ten charging outputs are possible.
Description
The device is rather simple, consisting of a transformer, rectifiers, current-reducing bulbs, and the necessary connections and enclosure. All the parts used in the prototype are available through Radio Shack or other electrical suppliers. A parts list is included at the end of this article; equivalent components should work as well.
The prototype parts layout is not critical, as this is strictly an AC-to-DC conversion. Each output must have its own bridge rectifier to isolate the Ni-Cd packs from one another. This allows several six- or seven-cell packs to be trickle-charged simultaneously without interaction. If you wish to charge larger packs, a higher-output-voltage transformer will be required.
Transformer and safety
The specified transformer has a rated output of 12.6 volts at 1.2 amperes and is sufficient for up to ten outputs. A 1-ampere-rated fuse protects the circuit in case of component failure. All other parts are over-rated for their tasks to ensure long, efficient life while maintaining low cost. Items such as the on-off switch and the indicator light are not required, but are convenient.
Outputs and connectors
The connecting plugs must match the type of connectors on your packs (Tamiya connectors are shown). Be certain to double-check their polarity before you install them.
The output current is limited to approximately 40 milliamperes (or less) by the bulbs placed in series with each output. This means the packs can be left on trickle charge indefinitely without harming them.
You will find that the Ni-Cd Topper will help keep your Ni-Cd packs performing at peak efficiency.
Author / Contact
Glenn Bolick 10256 Stratford Hall Ct. Mechanicsville, VA 23111-5162
Component List (Radio Shack part numbers are given)
- 270-224 Deluxe Project Case (1)
- 273-1352A Transformer, 12.6 volts at 1.2 amps (1)
- 276-1161A or 276-1152 Silicon Bridge Rectifier, 100 volts at 1 amp (4–10 as desired)
- 272-334A Micro 12-Volt Light (two per package), 60 mA (2–5 packages as desired)
- 272-331B Hi-Bright 12-Volt Light (two per package) (1)
- Tamiya or similar plugs (4–10 as desired)
- Fuse holder and 1-ampere fuse (1 each)
- Solder; switch (1)
- AC cord (1)
- 2 × 3-inch perforated electronic board (1)
- #22 or larger wire (5 feet)
Transcribed from original scans by AI. Minor OCR errors may remain.
