Lithium Polymer Battery
Lithium polymer is a kind of polymer made of lithium (li-poly or lipo or RC lipo)
There is a great deal of misunderstanding about lithium polymer batteries out there right now. A major reason for this is because the cells for which the name was first coined and the cells that are often referred to as lithium polymer cells today are not the same thing at all.
Remember when we spoke about the manufacturing process for lithium batteries? In what way do they consist of an anode, a cathode, and a fluid or more frequently gelled electrolyte substance sandwiched in between them? Right. Consequently, the original name “lithium polymer battery” referred to a novel kind of lithium cells that utilized a solid electrolyte (also known as “dry” electrolyte) rather than the more usual liquid or gelled electrolyte in place of the ordinary liquid.
It was a polymer, or a plastic substance, that was employed as the solid electrolyte in these experimental cells, which gave birth to the term “lithium polymer battery.”
Lithium Polymer vs Lithium Ion
The hope of this technological advances for dry electrolyte batteries was that they would be very safe. A large-scale production of the substance, however, was never achieved. The issue was that the dry electrolyte could not conduct electricity very quickly at room temperature, which was problematic. Therefore, in order to operate correctly, the batteries needed to be heated on a continuous basis. This clearly ruled out the majority of potential uses in this category. A large heater integrated inside a mobile phone or laptop is not something anybody wants.
As a result, the first lithium polymer batteries were never really successful. The confusion over the term arose when some producers began talking towards other cells that were packaged in polymer, such as pouch cells, as “lithium polymer” cells. This became perplexing since these cells did not really contain polymer electrolytes, but rather had their liquid electrolytes gelled with the help of an external polymer, which caused confusion.
These should actually be referred to as “lithium-ion polymer” cells, in order to differentiate them from the original, non-commercialized “lithium polymer” cells that were used in the first place. However, it was when people began referring to them as lithium polymer cells that the misunderstanding arose.
However, the perplexity does not end there! This is because what people started referring to as lithium polymer batteries (which were really lithium-ion polymer batteries in pouch cell forms) are virtually similar to the conventional lithium-ion batteries that were already in use at the time of their introduction. They use cathode and anode materials that are the same or comparable to one another, as well as electrolyte in similar quantities. A micro-porous electrolyte is used in lithium-ion polymer batteries rather than the usual porous separator layer that is put in the electrolyte of lithium-ion cells. This is the most significant distinction.
Is LiPo the same as Lithium Polymer
As a result, all “lithium-ion polymer” and “lithium-ion” batteries now on the market are technically lithium-ion batteries. Every one of them is the same in that they all work by transferring lithium ions back and forth via an electrolyte. However, the word “lipo,” which is an abbreviation for lithium polymer, is now widely used to refer to the form and type of cells, specifically pouch cells, the pouches of which are technically made of a polymer substance. Because of the widespread usage of the word “lipo,” many people now believe that a lipo cell is just another name for a pouch cell, which is incorrect.
In reality, a pouch cell is just a kind of battery cell structure that may be used to manufacture lithium-ion, lithium-iron-phosphate, and perhaps additional battery chemistries in the future. As a result, “pouch cell” refers to the form rather than the chemistry. However, it seems that everyone is now refers to pouch cells as “lipos” (li-polymer cells).
Finally, there is a whole class of lithium-ion cells that are specifically designed for use in radio-controlled (RC) toys and vehicles, which are referred to as lipo batteries. These are very high-capacity lithium-ion batteries that are especially designed for use in the radio-frequency sector because of their capability to provide the greatest potential current.
Nowadays, the word lipo is most often used to refer to the RC batteries that are commonly seen in RC vehicles. This is why throughout the rest of this article, I will refer to these high-capacity RC batteries as “RC lipo” batteries instead of “RC” batteries. Although this is not the original historical use of the word lithium polymer, it is the most frequently used convention today, and as a result, it is the way I shall refer to it in this article. When in Rome, do as the Romans do…
However, please be aware that the words lithium polymer, li-ion, and lipo are all used interchangeably in the industry, and there is a lot of misunderstanding about them. For the sake of this article, “RC lipo” shall refer to lithium ion batteries that are particularly intended for radio-controlled (RC) applications, while “li-ion” will refer to all other lithium ion batteries. I will not use the phrase “lithium polymer” since any cell on the market today that is marketed as “lithium polymer” is really simply lithium ion, and the true “lithium polymer” cells never made it out of the lab in the first place.
Lithium Polymer Battery Explosion
Phew! Okay, I apologize for taking so long to respond, but I believe it is essential to draw attention to the uncertainty and attempt to make sense of it. Now, let’s get down to business and learn concerning RC lipo batteries, which should be entertaining since these are the batteries that go poof when you tamper with them.
Let’s get this out of the way right now, shall we? RC lipo batteries are the most hazardous kind of battery. These are the ones that are eager to set your home on fire if you don’t charge and discharge them according to manufacturer’s instructions. They may be completely safe when used appropriately, but they can also be very volatile when used incorrectly.
Let’s take a look at what made RC lipo batteries so unique now that we’ve gotten that out of the way. RC lipo cells are a specialized chemical based on lithium cobalt that is well suited for use in high-capacity electric vehicles. They have the ability to produce very high discharge discharge rates over extended periods of time, as well as crazily high discharge rates for short periods of time (before they overheat and we get back to that unfortunate fire scenario I warned you about).
RC lipo cells are almost solely utilized in the remote control vehicle sector for applications like as RC drones, helicopters, aircraft, automobiles, and other vehicles. They are also employed in the military and law enforcement industries. These gadgets need the use of a tiny and lightweight battery that can provide very high discharge rates. Even though RC lipo cells aren’t the lightest cells available (they are variations of traditional li-ion cells), those who may provide much more power for just a small increase in weight.
Lithium Polymer Battery life
RC lipo cells are also the most affordable lithium-ion batteries on the market. They are much less expensive than lithium-ion and lithium-iron-phosphate (LiFePO4) cells (we will learn more about LiFePO4 cells soon), making them appealing for use in other applications that need DIY batteries, including certain electric bicycles batteries. Another significant disadvantage of RC lipo batteries (apart from the issue that they are essentially mini explosives which can also be used to power electronics) is that they have extremely short cycle lifetimes.
A RC lipo cell with a cycle life of 200 cycles would be regarded to have quite excellent performance. Certain RC lipos could be pushed closer to 300 cells, but they don’t last as long as li-ion cells and can’t really come halfway to LiFePO4 cells in terms of battery life and performance. (Please keep in mind that these cycle numbers are based on full charging and discharging cycles. The effects of partial charging and discharging on the life of almost all kinds of lithium battery cells will be explored later.)
A further disadvantage of RC lipo cells is that their charging procedure is more complex. In contrast to Lithium-ion and Lithium-ion-polymer (LiFePO4) cells, which are very simple to charge, RC lipo cells need more costly balance chargers to guarantee that all cells in a battery are kept at the correct voltage and synchronized with each other.
One of the reasons for this is that when RC lipo batteries deviate significantly from their rated voltage range, they become extremely volatile and dangerous. To gain a better understanding of what I’m talking about, search on YouTube for “overcharging RC lipo cell.” It is essential that RC lipo cells be charged within their designated voltage range in order to achieve maximum performance. They should never be released at a pressure that is too low.
Discharging a rechargeable lithium-ion battery to below 2.5 volts and then charging the battery may result in the cell catching fire, particularly at higher charging currents. In order to avoid this, RC lipo cells must be closely monitored during discharge in order to guarantee that they do not drain too far.
RC lipo batteries that’ve been excessively discharged may be recharged, however this must be done at extremely low currents and can potentially result in a fire depending on how much the battery cell has been damaged. Idealistically, this would not be tried, but it should be done in a controlled setting and away from anything that might catch fire or ignite the surroundings.
Lithium Polymer Battery Charging Tips
A nominal voltage of 3.7 V is provided by RC lipo cells, which are electro-chemically comparable to lithium-ion batteries. Nonetheless, since it is important to avoid over-discharging the cells, it is not advised to discharge them to a voltage lower than 3.5 volts. Attempting to get a higher voltage of 3.2 V is regarded to be safer. Many pilots in the radio-controlled aircraft field will cease flying when the battery voltage gets as high as 3.5 V, thus preserving a greater safety margin. This means that the maximum voltage of RC lipo cells should never be higher than 4.2 V.
In addition, it should have been noted that certain voltages are referred to as the “under load” voltages. According to the present load, a lithium battery cell (of any chemistry) will experience a decrease in voltage level. Voltage sag is the term used to describe this decrease in voltage. When in operation, an RC lipo cell should never be allowed to dip below 3.0V.
The reference voltage recorded after the load is removed will return to a higher level, most likely in the 3.3-3.5 V range, though an even safer level for at-rest voltage is around 3.7 V. If discharge stops at 3.0 V under load, the reference voltage measured just after load is removed will revert back to a higher level, most likely in the 3.3 V-3.5 V range, though an even safer level for at-rest voltage is around 3.0 V. In order to guarantee that RC lipo cells do not over discharge beyond a safe limit while under load, it is essential to continuously check their performance under load.