Brushless Radio Controlled Cars
News, reviews, tuning and hop-
RC LiPo Battery Charging Guide
Part 1 Part 2
More information on LiPo batteries...
What is a Lithium Polymer Battery?
In a nutshell, a battery consists of two metals immersed in an electrolyte solution. A chemical reaction takes place that causes electrons to flow from one metal to the other. This produces a voltage difference between the positive and negative poles. When a load (such as a motor) is placed between the two poles, electrons will flow through the circuit until the metals are chemically neutralized (battery dead).
The voltage produced between the two metals is called the electrochemical potential. This energy is directly related to the types of metal used in the battery.
Lithium is the lightest metal in the universe and has the highest electrochemical potential. Lithium would be perfect for making lightweight powerful batteries right?
Well, almost... Because lithium metal is very unstable, battery manufacturers began
using non-
Voltage and Capacity of LiPo Battery Packs
Each individual lithium polymer cell has a nominal voltage of 3.7 volts. It is extremely important that a LiPo battery cell is not discharged below 3.0 volts or charged beyond 4.2 volts. Doing so will damage the battery.
Electronic speed controllers (ESC's) designed for LiPo battery packs have a Low Voltage Cutoff (LVC) that will automatically cut the power to the motor when the battery voltage (of an individual cell) reaches 3.0 volts.
To understand how LiPo battery packs are put together, you need to have a basic understanding of voltage and capacity. If you are not familiar with batteries, think of voltage as the "muscle" and capacity as the "energy" of a battery.
LiPo Balancers
As stated above, lithium polymer cells must stay between 3.0V and 4.2V for optimal performance. A standard LiPo charger looks at voltage of the entire LiPo battery pack when charging. Some times the individual LiPo cells become unbalanced over time. For example, one cell may have a voltage of 3.8V while the rest are at 4.2V.
A LiPo balancer monitors and controls how much each cell in the LiPo pack is charged or discharged. Balancing the pack will allow for the fullest possible safe voltage which results in more power while in flight. A balanced pack also tends to last longer as no individual LiPo cells become over charged.
Torque RC .com 2011
Storing LiPo Battery Packs
LiPo batteries should always be stored in a cool environment. In other words, don't leave them in your car with the windows up on a hot summer's day. Keep them in a cool location out of the direct sunlight. It is highly recommended that Lipo batteries be kept in a charging bag while be charged and while not in used. A charging bag is a very cheap form of insurance!
Advantages of LiPo Batteries
- Have nearly double the capacity with half the weight of NiCad or NiMH battery packs
- Retain charge significantly longer than NiCad or NiMH batteries when not being used
- Do not develop a "memory" as NiCad batteries do
- With LiPo cells in combination of series and parallel, LiPo packs can be built to power almost all RC models.
Disadvantages of LiPo Batteries
- Have very short shelf life of two to three years
- Very sensitive to high temperatures
- Very sensitive to high and low voltages. Exceeding either will damage the battery
- Prone to explode if exposed to heat, or charged/discharged improperly
Remember
Safety FIRST
When using LiPo Batteries
