Do It Yourself Battery Packs

By Philip Sarelis

Every R/C Modeler needs a battery pack to power their crafts, and of course the radio, too. Here's an article that is sure to give you the insight to create your own AA packs in any configuration you need for your application, for less money than you had thought. Whether you need a cell for your boat, plane, car, watch, camera, straight razor, mustache trimmer, ipod, flashlight, , gps, wind speed indicator, etc., Battery Companies continue to deliver higher capacity higher quality cells, enabling us to enjoy our electronics longer, and improve the performance.

Although Alkalines or what are commonly referred to as dry cells, deliver higher voltages, which is a must for standing in close quarters amongst other transmitters to attain the stronger reception and ultimate clarity, they will not provide the long run times and are not as environmentally friendly. With a good quality charger that will terminate charging either by temperature or voltage and not by time, rechargeables can be dialed to outperform the alkalines, retaining higher voltages longer, more amperage, and recharged hundreds of times. Thus yielding a more enjoyable time, beacause in any R/C Model Sport repeatability is the key. Contrary to Dad's or Grand Dad's charger from the 60's and 70's, it is dangerous to recharge Alkalines.

I needed some cells quickly, and a tip from a fellow R/C car racer lead me to the electronics department of a retail store that just happened to be named Whale Mart. There I found the latest and greatest AA cells for my application. Energizer is retailing 2500 mAh AA cells for /#/$2 each. Weight of each cell is 1.1 oz. (30g), heavier than the industrial 1800's and 1650's that we usually get from Hobby Shops, battery retailers, online discount sites, and well worth the weight. I do not recommend the toy charger that is sold with these batteries, just buy the cells. These cells are 4 times the capacity of most receiver packs that you get with a new radio which are /#/600 mAh. Sail all day long (6 hours) without recharging in the field and with no battery memory as found with NiCad's.

Too heavy for your Yacht, Sailplane, or Park Flyer? Lower capacity cells can be found on the shelves as well as AAA, and LiPo's.

What you'll need:

  • Batteries: Most receiver packs are 4.8v, and 6.0v can be used for sailwinch systems. Consequently, the higher voltage and higher amperage draws needed for these powerful motors, actually decreases the life of the servos and the 5 cell 6.0v packs last about as long as the 4 cell 4.8v packs.
  • Soldering tool capable of 800° (solder station)
  • Solder-unleaded
  • Fine sand paper
  • Copper De-soldering braid
  • Wire cutter/stripper
  • Hobby or Battery Vise
  • Battery connector (J plug, Z plug, Zero Loss, Deans, etc)
  • Strapping tape
  • Shoe-Goo (silicone)
  • Small fan for cooling
  • Quality battery charger - Choose one that will charge with 1 amp or less and terminate when charging is peaked, Peak Charger.

Begin by deciding the best configuration for your model. Flat, stick, nested, brick, hump, and saddle, are all terms used to describe battery configurations. Since batteries double as ballast, you could strategically place them in the hull to your advantage. Think low and inside, and I'm not talking baseball here. Move the batteries aft on the windy days and forward on the light days if your Class Rules allow it but, never change a battery pack with a different one (weight) during a regatta. Automatic DQ.

Lightly scuff all the battery terminals with fine sand paper. This makes it easier for the solder to stick to the cell. Using strapping tape, form the pack being conscience of how the connections will be soldered. If all the batteries will be in series then the cells must be opposite of each other. Solder just a spot of solder to each terminal. This will also pre-heat the surface so you won't need much heat during the actual soldering process. Cut some de-soldering braid to the length to cover the terminals without touching the cell's outer edge. For AA size, 5/8" is plenty. Once the batteries are tightly taped together and you are satisfied, put the pack in a holder or hobby vise and start soldering. It helps to use some silicone or Shoe-Goo to adhere the cells to each other to alleviate any stress on the solder connections. Batteries don't like heat so do not hold the iron down very long. Wipe off any excess solder on the braid between the cells for a lower resistance connection.

Nickel Metal Hydride (NiMh) and Nickel Cadmium (NiCad) cells perform at their best after at least 4 cycles of charging and depletion. NiCads will develop a charge memory and need to be depleted before every charge while NiMh's are happy in any state. Never ever short cells to 0 volts. That's great way to ruin a good cell not to mention potentially starting a fire.

Please dispose of all rechargeable batteries properly, our R/C hobbies are at stake.

Use the images below as references.

battery in vise

Work with batteries secured in a holder such as an Xacto hobby vise
battery on discharger

Very good idea to cool the pack after soldering and before charging. Never charge a hot battery. Shoe-Goo (silicone) was used to adhere the cells to prevent accidentally breaking the connections. Just a little dab will do ya. Too much will preven them from cooling properly.
did it myself battery

The final product ready to cycle and use. A solder with a high silver content was used. Total weight of pack is 4.2 oz or 120 grams. The container that the batteries are sold in makes a very convenient jig to form your packs after adding the silicone between them.

The AMYA is not responsible for any injuries, or property damage as a result of soldering or battery misuse.