The term ‘LIPO’ is derived from the words Lithium and Polymer. A LIPO battery is a lithium-ion polymer battery with rechargeable properties based on lithium-ion technology and uses a polymer electrolyte. The LIPO battery is a storage battery that can be recharged over time with a highly dense energy and low rate of discharge, that uses macromolecules as electrically conducting solution.
The "S" stands for a cell; a 1s LIPO battery therefore is a LIPO battery with one cell. LIPO battery voltage is specified by the number of cells in series, each cell has a nominal voltage 3.7V. LIPO batteries are preferably labelled as 1S, 2S, 3S, etc. "P” on the other hand, stands for the number of cells in parallel; for instance, a 2S1P means “2 cells in series and 1 cell in parallel.
The mentioned nominal voltage is for an ideal battery; actual batteries don’t behave this way, instead they start at a higher voltage and then their voltage will slowly decrease as the battery is discharged. So while an ideal battery might have a voltage of 3.7 V during the entire time it is discharging, an actual battery will start at the maximum voltage of 4.2 V and as itt discharges, it keeps decreasing till zero if not properly checked. Manufacturers recommend a certain minimum voltage, called the cut-off voltage; and for LIPO batteries, it is 3.0 Volts. In practice, the voltage alarm is set higher than 3.0 V, preferably 3.3V, to allow the safe landing of the quadcopter before it drops below 3.0 V.
A 1S LIPO has the following properties:
- A nominal Voltage of 3.7V
- A maximum operating Voltage Range of 2.75V to 4.20V
- A maximum charge Voltage of 4.2V with an allowance of ±50mV
- A rated capacity of 1500mAmp- hr for a 1500mAh type Battery, an hour.
Note that the capacity of a battery is anindication of the total energy that a battery can store; and it is inversely related to current. basically, the higher the capacity, the longer your battery will last.
- A power rating of 3.7Wh
- A continuous Discharge Current of 1500mA
- A discharge Cut Off of 2.75V
- An internal Impedance less than 120m?
- An expected life cycle of 500 cycles producing an efficiency of 80% or more.
1S LIPO batteries are mainly used in several consumer electronic devices and in devices where the weight of the material is of concern, like in mobile gadgets (mp3 players)
HOW DO YOU PARALLEL CHARGE 1S LIPO BATTERY?
Connecting several 1S LIPO batteries in parallel, they equalize depending on their voltage differential; due to initial surge pulse of current, it is recommended to keep the voltage of the cells being parallel charged within a safe volt of 0.5V to each other. Charging different 1S type LIPO cells in series, results in unbalancing, a balancer is then needed to rectify this.
However, in the absence of a balancer, 1S batteries or cells can be charged individually or in parallel. Individual charging has no special precautions, but parallel charging, requires maximum attention to monitor the voltages of the cells you are paralleling together to charge, and it is best to keep the voltage difference is at less than or equal to 0.5 volts.
In the case of greater imalance, charging starts from the lowest voltage cell, then as it rises to the value of the next cell, or cells, they are added in. Parallel charging is very safe, but attehtion must be given to the initial balancing currents involved when cells are arranged in parallel.
Parallel charging a 1S LIPO battery basically involved arranging the 1S batteries in parallel before charging, taking note of the initial current of the individual batteries, and setting charger cell count to 1 cell, adjust the charging current to a 1C rate for the lowest capacity cell.
Parallel charging charges all batteries at once; if the batteries are all at the same level of current, it takes all batteries as one with 3.7v and charges at the capacities of one of the batteries.
HOW LONG DOES IT TAKE TO CHARGE A 1S LIPO BATTERY?
The rate of charging a 1S LIPO battery depends on the current applied, but care must be taken not to exceed the current specification for the battery. For instance, a 1000mAh battery, charging at 1000mA will fully charge that battery in 1 hour, while charging it at 500mA will take twice as long, i.e. 2 hours.
The 1C rate charges a fully discharged battery in about an hour. To improve the life of the 1S LIPO batteries, it is important not to fully discharge them i.e. do not exceed about 80% of the battery percentage; a battery at 80% discharge would measure about 3.7V after resting from use.
HOW CAN YOU CHARGE A 1S LIPO BATTERY?
1S LIPO batteries can be charged using the appropriate charger specified for it; first, a power source is connected to the charger, so it can regulate power to the battery. The power supply is connected to either of the barrel jack (with a spec of 5.5mm outer diameter and 2.1mm center pole) or a mini-B USB connector for the charger.
In charging the 1S LIPO batteries, the power supply voltage should be kept between the range of 4.75 and 6V. A 5V USB supply from a mini-B cable connected to either a computer USB port or wall adapter makes a perfect power source, or using the barrel jack input with a 5V wall adapter. After connecting the charger to a power supply, the next step is to connect the battery. Single cell batteries with a nominal voltage output of about 3.7V gets up to around 4.2V at a full charge. To avoid explosions, a current of 1C maximum should not be exceeded, i.e. a 500mAh battery should not be given a charge current over 500mA and a 100mAh should not be charged higher than 100mA.
When charging, it is important to know the battery's capacity and the charge current supplied by the charger.
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