This article assumes that you have a basic knowledge of electronics. If you don't, consult a local hobby shop for help before attempting this.
One of the main reasons for building (or rebuilding) battery packs, other than the cost savings, is the ability to improve the connections between the cells so the current will flow more easily from one cell to the next with the least amount of resistance. Resistance causes the cells to overwork themselves and heat up. Heat is bad for battery life and performance. The hotter the pack is, the less runtime, current, and life it will give and have. And the hotter your battery runs, the more resistance there will be.
A common misconception about battery packs is that they are one very large battery when they are actually made up of a number of individual batteries, called cells, that are connected together to work as a single pack. There two basic types of battery packs. Stick packs, or shot-gun, stack the batteries positive to negative ends like batteries in a flashlight. Brick, or side-by-side packs have cells laid next to each other forming a cube or “brick”. Which style you use depends on the space available and the voltage you need for your particular model. This information is generally found in the “Items Needed to Complete” section.
There are two ways that the cells can be connected together. “In Series” is where the positive terminal of one cell is wired to the negative terminal of another cell. With this method, the total voltage of the pack is the sum of the individual cell voltages. For example, a 6-cell NiCd or NiMH pack is made up of cells rated at a nominal 1.2 volts each. When wired in series the total nominal voltage of the pack is the number of cells in the pack (6) multiplied by the voltage of each cell (1.2V in this case) to get the total pack nominal voltage (7.2 volts for this example). This is the most common cell connection method found in the RC hobby.
The second is called “Parallel” where you connect the positive terminal of one cell to the positive terminal of another, and negative terminal of one cell to the negative of another. Wiring cells in Parallel increases the total capacity of the pack but the nominal voltage remains that of a single cell. To figure out the actual end result capacity add the mAh rating (milli-amp hour) of the cells. If you put 2 cells in parallel that are each 2100mAh (commonly referred to as “2P”), multiply 2100 by 2 for a total capacity of 4200mAh.
The number of cells you’ll need and the configuration of them in your battery pack will depend on what you are powering, how much power you need, the amount of space you have to hold that battery pack, and the weight distribution in your vehicle. In some cases your chassis space for a battery pack is not adaptable, so be aware of those constraints before you start. Check your owner’s manual for your vehicle’s specifications. It can also be very helpful to draw out the cell configuration and double check your connections and voltage requirement before you begin assembly.
Lay out all the parts and tools you'll be using on your heat resistant work table so you won't have to get up for anything. Make sure each cell is fully discharged to reduce the chance of an accidental short during the assembly process causing serious damage or harm. Make sure you follow all safety precautions for soldering tools, equipment, and chemical based batteries.
CAUTION: If it takes you more than a second or two at this point you can cause damage to the battery and / or reduce its performance.
CAUTION: it should take between 5 - 7 seconds to solder each joint. Any longer and you risk damaging or overheating the battery.
Acid Core Solder: Solder with an acid flux in the center. It is used for soldering more difficult metals, such as galvanized iron. Soldered surfaces should be washed after each soldering to remove the corrosive effect of the acid.
Ampere: A unit of measure of the rate of electron flow or current in an electrical conductor. One ampere of current represents one coulomb of electrical charge (6.24 x 1018 charge carriers) moving past a specific point in one second.
AWG: American wire gauge (AWG) is a standardized wire gauge system used since 1857 predominantly in the United States for the diameters of round, solid, nonferrous (not iron based), electrically conducting wire.
Battery Bar: Strips of solid metal and some times braided wire strands that are used to connect and carry the current between cells in a battery pack.
Battery Pack: A group of any number of (preferably) identical batteries or individual battery cells configured to work together to deliver a desired voltage or power density.
Brick Pack: When cells in a battery pack are arranged side-by-side creating a cube or “brick”. Also called side-by-side packs.
Cell: A single battery in a battery pack.
Current: Essentially how fast electrons are moving in a circuit. It is measured in amperes (amps). Current (Amps) = Potential (Volts) / Resistance (Ohms)
Desoldering Braid: See soldering wick.
Desoldering Wick: See soldering wick.
ESC: Short for Electronic Speed Control. It sends power to the motor, and tells how much power to give it, in relation to trigger movement on the remote.
Flux: A chemical cleaning agent which facilitates soldering, brazing, and welding by removing oxidation from the metals being joined.
Jig: A devise used to hold the correct positional relationship between a piece of work and the tool or between parts of work during assembly.
LiPo: Short for lithium polymer, a lithium based rechargeable battery that uses a polymer case allowing it to be lighter and specifically shaped for its application and offer a very high capacity for its weight. They need to be carefully monitored during charging as overcharging or charging a physically damaged or over discharged cell can be a potential fire hazard.
Nicad, NiCd: Short for Nickel Cadmium, a type of rechargeable battery used for RC products. They are relatively inexpensive. They need to be fully discharged after each and every use. If not, they will not discharge to their full potential on subsequent discharge cycles.
NiMH, NI-MH: Short for Nickel-Metal Hydride, a type of rechargeable battery used for RC products. They have a significantly higher energy potential (capacity) in cells approximately the same size and weight of comparable NiCd cells and they don’t require complete discharge between charging. They were developed as an alternative to Nickel Cadmium cells.
Milliampere-hour: Designated as mAh. It is one-thousandth of an ampere and used to describe how much electrical charge a particular battery will hold, especially for small batteries.
Multi-Meter: An electronic measuring instrument that combines several measurement functions in one unit. A typical multi-meter may include the ability to measure voltage, current and resistance. Also known as a volt/ohm meter or VOM.
Parallel: A configuration for connecting cells in a battery pack where the positive terminal of one cell is connected to the positive terminal of another, and negative terminal of one cell to the negative of another. Polarity: Refers to the direction of electron flow. The polarity in cells is indicated by a positive (+) end (terminal) and a negative (-) end. Electrons move from negative to positive.
Resistance: Describes how easily electricity flows through a material. Where resistance is high more effort is needed. A smaller-diameter electrical wire has more resistance to electrical flow than a larger-diameter wire. It’s measured in units called ohms.
Rosin Core Solder: Solder with a rosin flux in the center. Used for soldering electrical wiring.
Series: A configuration for connecting cells in a battery pack where the positive terminal of one cell is wired to the negative terminal of the next cell, which is wired to the positive terminal of the next cell, and so forth.
Soldering Wick: Usually found as a roll of fine, braided 18 to 42 AWG wire of high conductivity electrical copper, which has been treated with a rosin solder flux. In RC it is an option used to connect cells in a pack. It is also used for removing solder from any solder joint. Also called desoldering wick or desoldering braid.
Stick Pack: When cells in a battery pack are connected in a line, positive to negative like batteries in a flashlight. Also called shotgun packs.
Tinning: The process of coating a metal with a thin layer of solder. Tinning is often done to make attaching components and wires easier and quicker.
Voltage: The rate at which energy is drawn from a source that produces a flow of electricity in a circuit; the measurement of electrical pressure.
Watts: Watts is a measure of the amount of electricity being used; a rate of electrical power consumption. The formula for determining how many watts an electrical circuit can carry or how many watts an electrical device will require is Watts = Volts x Amps.
This free how to is courtesy of
Inland Craft Products, Co.
32052 Edward Drive
Madison Heights MI 48071