Lipo Battery User Guide

By Published Batteries & Chargers

Kindly Follow the link purchasing various Li-po batteries explained in the blog below,

Li-po Batteries

Introduction:

Li-Po battery is a rechargeable battery that has evolved RC world to a new horizon. It provides a viable power source option over fuel powered Planes, Helicopter and Multi-rotors.

Li-Po works on the principle of intercalation and de-intercalation of lithium ions from a positive electrode material and a negative electrode material, with the liquid electrolyte providing a conductive medium. To prevent the electrodes from touching each other directly, a micro porous separator is placed in-between which allows only the ions and not the electrode particles to migrate from one side against the other.

Cell arrangement:

  • The format xSyP (where x and y are integers) describes the connection arrangement of the cells connected to a battery pack.
  • S and P stands for Series and Parallel respectively. As you may know, series adds the voltage of the cells and parallel adds the capacity of the cells, so a combination of cells in series and parallel results in a battery pack.
  • Batteries are made up of cells, whose voltage is determined by cell chemistry and whose capacity is determined by energy density and physical size of the cell.

A battery is defined through rating system which allows us to compare the properties of a battery and support us to determine which battery pack is suitable for application in hand.

There are four main ratings that needs to be observed for a Li-Po battery.

  1. Capacity
  2. Voltage/Cell Count
  3. Discharge Rating
  4. Charge Rating

Capacity:

The capacity of a battery is basically a measure of how much power the battery can hold. The unit of battery is milliamp hour (mAh). This is saying how much drain can be put on the battery to discharge it in one hour.

Voltage:

The voltage of a battery is also determined by the cell arrangement (series), and there are few common voltage measurements worth noting:

  • Charged – The voltage of a fully-charged Li-Po cell is 4.20V, and charging above this would damage the cell.
  • Nominal – This can be considered a sort of “half-charged” voltage, as it is 3.70V, in between charged and discharged. Nominal voltage is what manufacturers use when describing the voltage of their batteries. The battery should be stored at this voltage.
  • Discharged – The voltage of a discharged Li-Po cell is 3.20V, and discharging below this will definitely damage the cell.

Cell Maintenance: Never store any Li-Po battery fully charged. Storing the battery fully charged will result in puffing up of battery due to gas generation through a process called electrolyte decomposition. The recommend storage voltage is 3.7 V to 3.85 V. Most chargers will allow to discharge Li-Po until storage voltage is achieved under balance mode.

Discharge Rating:

Constant C Rating (Discharge) – The constant C rating (in relation to discharge) tells you how many amps can be safely drawn from the battery constantly. The “C” in a rating of xC (where x is an integer) actually stands for the capacity of the battery in Ah (ampere hour). By multiplying the C rating’s coefficient by the capacity of the battery in Ah, you can determine the sort of amperage you can draw.

Charge Rating:

C Rating (Charge) – Determined in the same fashion as the C rating for discharge, the C rating for charge tells at what amperage one can safely charge the li-po battery.

 

Charging and Discharging for Li-Po Batteries:

All Li-Po batteries (should) have 2 sets of wires coming out of them:

Discharge leads:

The discharge leads are the thicker wires of which there are a positive (red, +, anode) and negative (black, -, cathode), and are used to discharge the Li-Po as their name suggests.

Balance leads (sometimes called balance taps):

The balance leads are used when charging the battery to ensure that all the cells in the battery are charged equally. There is generally a common ground connection on one side of the balance connector, as well as a positive connection to each cell in the battery. Therefore, depending on the number of cells the battery has, it will have a balance connector with a different number of pins.

Charging Characteristics:

  • Power Input – You need to supply more power to your charger than its output due to inefficiency.
  • Power Output – Device specific output power limitation. As wattage is the product of voltage and current, so your maximum current you use to charge your battery depends on your battery’s voltage and vice versa. However, chargers also have a max/min voltage and max/min current output in addition to their wattage limitations.
  • Balancing – Balancing cells is quite possibly the most important part of charging a Li-Po battery. As Li-Po batteries are used, their cells may discharge unevenly and become “unbalanced.” To combat this, balancing chargers have balance plug inserted into the balancing leads of the Li-Po battery as well as the discharge leads, allowing them to individually charge and “balance” the cells within the Li-Po battery so that all the cells are the same voltage (4.20V) at the end of the charge.

Ideal Charges for Li-po:

IMAX B6-AC Charger/Discharger 1-6 Cells

IMAX B6 5A Multipurpouse Battery Charger

Li-Ion / Li-Po 3A Balance Charger for 2-4 Cell Battery

 

Safety precautions:

  • Pick up Li-Po batteries by the body of Li-Po and not with the wires. It can easily break a solder joint inside the Li-Po.
  • Be sure that the correct polarity is observed when connecting the battery pack to charger.
  • Don’t leave Li-Po batteries near a heat source.
  • Do not charge batteries near flammable items or liquids.
  • Keep sharp things away from Li-Po batteries. Poking a hole in the foil wrapper of a Li-Po battery ruins it and can lead to fire.
  • Don’t drop a Li-Po, even from a short distance. Denting/crushing a Li-Po battery can cause an internal short and can cause fire.
  • Be absolutely sure that the Lithium Polymer charger settings are correct for the battery pack being charged – (both voltage and current settings).
  • Li-Po batteries must be CHARGED and STORED in a fire-safe container like a Li-Po safe Bag.
  • Always wait at least 15 minutes after using a Li-Po to let it cool down before charging it. This prolongs the life of the Li-Po and prevents possible overheating and damage.