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Understanding RC Batteries

2/8/2010 by Gary Katzer

Copyright:© 2010 Horizon Hobby, Inc.

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Whether you run a nitro or electric car - regardless of scale, size or speed - your RC vehicle is going to use a battery pack of some type. Unfortunately getting the right battery for your vehicle isn't quite as simple as going down to the local hardware store and picking up a pack off the rack. With so many different sizes, types, chemical compositions and designs, getting the right battery for your application can take some research. We've done the legwork to try to help answer some of the most basic questions for you regarding Ni-Cd, Ni-MH and Li-Po battery packs. From charging, discharging, storage and more - we have you covered.

In addition to the information in the video we have put together a list of common terms used when talking about RC battery packs.

Battery Pack
An assembly of individual batteries that are connected in a way to increase the total voltage, total capacity or both.

Cells
Another name for the individual batteries used in the construction of battery packs. Common configurations can be found below.

Sub-C
The typical size of a rechargeable Ni-MH or Ni-Cd battery pack for use in an RC car, truck or boat. A Sub-C looks similar to a traditional alkaline C-sized battery but is slightly smaller.

Ni-Cd
This abbreviation stands for Nickel Cadmium, a chemical compound used in rechargeable batteries. Ni-Cd batteries tend to be inexpensive however they are limited in terms of performance, cycle life and runtime. Ni-Cd batteries are very susceptible to "memory" problems if they are not completely discharged. The performance of a Ni-Cd battery pack tends to be reduced by multiple charges in a single day.

Ni-MH
This abbreviation stands for Nickel Metal Hydride, a chemical compound used in rechargeable batteries. Ni-MH batteries tend to have improved performance and cycle life when compared to Ni-Cd batteries. Ni-MH batteries have fewer "memory" issues than Ni-Cd battery packs and can be run multiple times in a day without a detrimental impact on the overall performance of the pack. They are also more environmentally friendly and easier to dispose of.

Li-Po
This abbreviation stands for Lithium Polymer, a chemical compound used in rechargeable batteries. Li-Po batteries are a totally different design and construction than Ni-MH or Ni-Cd batteries. Due to the average voltage of individual Li-Po cells the overall voltage of a Li-Po battery will be higher than a comparable Ni-Cd or Ni-MH battery pack. Li-Po batteries are also considerably lighter than their Ni-Cd or Ni-MH cousins. Li-Po batteries can be run multiple times in a day without an appreciable reduction in performance or runtime. Li-Po batteries do need to be charged with Li-Po specific chargers.

4.8V
The rated voltage output of a conventional 4-cell Ni-MH or Ni-Cd battery pack. This is accomplished by multiplying the voltage of the individual cells (1.2V) by the number of cells (4).

7.2V
The rated voltage output of a conventional 6-cell Ni-MH or Ni-Cd battery pack. This is accomplished by multiplying the voltage of the individual cells (1.2V) by the number of cells (6).

7.4V
The rated voltage output of a 2-cell Li-Po battery pack. This is accomplished by multiplying the voltage of the individual cells (3.7V) by the number of cells (2).

8.4V
The rated voltage output of a conventional 7-cell Ni-MH or Ni-Cd battery pack. This is accomplished by multiplying the voltage of the individual cells (1.2V) by the number of cells (7).

11.1V
The rated voltage output of a 3-cell Li-Po battery pack. This is accomplished by multiplying the voltage of the individual cells (3.7V) by the number of cells (3).

14.8V
The rated voltage output of a 4-cell Li-Po battery pack. This is accomplished by multiplying the voltage of the individual cells (3.7V) by the number of cells (4).

mAh (Milliamp Hour)
A measure of a battery's capacity. The larger the number of milliamps the longer the battery cell will last.

Peak Detection
Refers to a type of Ni-Cd or Ni-MH battery charger that automatically shuts off when a battery is fully charged.

CC/CV
Constant Current/Constant Voltage. This is the type of battery charger required for charging Li-Po batteries.

Charge Rate
The output of a battery charger, generally rated in amps.

1C
This refers to the charge rate that should be used with most Li-Po batteries. 1C refers to charging at a rate that is 1/1000 the capacity of the battery. For example a 1C charge rate for a 5000mAh battery would be 5-amps.

C-Rating
Refers to the amperage output of a Li-Po battery pack. A higher C-rating translates to a battery capable of handling a higher amp load placed upon it.

Balance Plug
Located on newer Li-Po batteries with two or more cells; Balance Plugs can be connected to external devices to monitor the voltage of separate cells in the pack individually. Balancing is done to ensure each of the cells in the pack is charged to the same state.