Traxxas Battery Basics

Article #76387

Traxxas Battery Basics

NiMH, NiCd, LiIon, LiFe, and LiPo
These terms refer to the materials and chemistry within the battery. Nickel batteries (NiMH, NiCd) have cells with the familiar “cylinder with a button on top” construction and a metallic case. Lithium batteries (LiPo, LiIon, LiFe) are usually constructed of flat cells stacked together. The cells may be encased in heat-shrink to form the final pack, or enclosed in a “hard case.” Traxxas Power Cell LiPos use a “semi-rigid” design that is durable and allows greater battery capacity in a pack of a given size.

NiMH = Nickel-metal hydride
LiIon = Lithium Ion
LiFe = Lithium Ferrous Oxide
LiPo = Lithium Polymer

Capacity
A battery’s capacity refers to the amount of energy the pack can store. Think of capacity as your model’s gas tank; the greater the capacity, the larger the gas tank, and the longer your model can run per charge. In addition to giving your model a longer run time per charge, using a pack with greater capacity also increases “punch,” the feeling of power you get when your accelerating from a standstill or out of turns. The large number (3300, 4000, 5800, etc) on your LiPo battery refers to its capacity in milliamp-hours (mah).

One milliamp is a thousandth of an amp, and amps are the measure of load or “current draw” on the battery. To convert milliamps to amps, divide by 1000; for example, 7600mah is equal to 7.6 amps. Milliamp-hours, or amp-hours, refers to the amount of current draw the battery can sustain for one hour. To continue with the example of a 7600mah battery, it would handle a load of 7600 milliamps (or 7.6 amps) for one hour. Since your powerful Traxxas R/C vehicle will likely draw more than 7.6 amps, it will run less than an hour per charge. The important thing to remember is this; the larger the capacity number, the longer your run time.

Voltage
The more voltage a battery has, the faster your car will go. Battery voltage is determined by the number of cells in the battery. Power Cell NiMH cells deliver 1.2 volts each; a 6-cell pack has 7.2 volts, a 7-cell pack has 8.4 volts, and an 8-cell pack has 9.6 volts. LiPo cells have higher voltage: 3.7 volts per cell. Because of this, they need fewer cells to provide the voltage needed for high-performance R/C. Power Cell LiPos are available with 2 cells (7.4 volts) and 3 cells (11.1 volts).

C-Rating
C is short for capacity. The load a battery can sustain is indicated as a multiple of capacity. For example, a load of 1C for a 7600mah battery is 7600 milliamps or 7.6 amps. A 2C load would be double the capacity; 15.2 amps (7.6 x 2 = 15.2). All Traxxas LiPo batteries are rated for 25C. For our example of a 7600mah pack, that would be 7.6 x 25 = 190 amps. How much amperage can be used to charge a battery may also be indicated as a “C” value. All Traxxas Power Cell LiPo batteries have a recommended charge rate of 1C, and a maximum charge rate of 2C. For maximum performance and longevity, charge at 1C whenever possible. For example, a 1C charge rate for the 5800mah Power Cell LiPo would be 5.8 amps. A 2C charge rate for the same battery would be 11.6 amps. An important note about C-Rating: Each battery manufacturer has their own formula and methodology for determining the C-Rating they assign to their LiPo batteries. For example, a Traxxas 25C battery evaluated using another brand's method of calculating C-Rating might be determined to have a 50C rating. For this reason, you should not compare batteries from different manufacturers by their C-Ratings.

2S, 3S
LiPo batteries contain 2 or 3 cells connected in series (S). So, a pack with 2 cells is a “2S” battery, and a pack with 3 cells is a “3S” battery. A 2S battery has 7.4 volts, and a 3S battery has 11.1 volts. If your vehicle or speed control is rated for “6S” and has two battery plugs (such as the E-Revo Brushless Edition), you can plug two 3S packs into it for a total of 6S. Two 2S packs would be “4S.”

“Series” connection means the cells are connected inside the pack so the first cell’s positive tab is connected to the second cell’s negative tab. This combines their voltages; the two 3.7 volt cells deliver 7.4 volts combined. The other way to connect the cells is in parallel (P), which means the cell’s are tabs are connected “positive to positive” and "negative to negative.” This combines their capacities. If you look at the specifications of your Power Cell LiPo, you may see that your 2S pack is actually 2S2P, meaning it has two pairs of cells, each connected in parallel (2P), and the two pairs of cells are then connected in series (2S).

Chargers for RC Batteries
It is critical for the longevity of your batteries and your personal safety that you always use the correct charger or charger settings for your battery, and observe all the precautions outlined in your battery and charger documents. Traxxas offers the #2930 EZ-Peak and #2932 EZ-Peak 2amp chargers exclusively for use with NiMH and NiCd batteries ONLY. NEVER use a NiMH or NiCd charger to charge a Traxxas LiPo battery. Failure to use LiPo balance charger to charge LiPo batteries can result in explosion, fire, and personal injury! The #2933 EZ-Peak Plus can be used with all R/C battery types including Lithium batteries, but you must be sure to select the LiPo, LiIon, or LiFe mode when charging Lithium batteries. Always place your LiPo battery in a fire-retardant bag or case while charging.  All rechargeable batteries should be charged in a charging bag or case.