Taking Care of a Portable Lithium-Ion Battery
First developed for portable electronics, lithium batteries are now used in many consumer and industrial products. They are also the primary power source in electric vehicles and grid energy storage systems.
They offer higher gravimetric and volumetric energy densities than other rechargeable battery chemistries. They are low maintenance, requiring no scheduled cycling to prolong their life.
Lightweight
Unlike other battery types, lithium-ion batteries offer the highest energy density per unit mass and volume. During the discharge cycle, lithium ions move from the anode through an electrolyte solution to the cathode where they recombine with electrons and are electrically neutralized. This process occurs in micro-permeable separators between the anode and cathode.
Lithium-ion batteries are commonly used in power banks, laptops and cell phones, largely due to their high power-to-weight ratio, excellent high temperature performance and low self-discharge. Their rechargeability also makes them more economical to use than other battery types.
These batteries use a variety of electrode materials, although lithium cobalt oxide is the most common. They also have Portable lithium-ion battery various electrolyte options including ethylene carbonate and lithium ion polymer. The latter uses a dry polymer electrolyte which allows for very slim geometry and simplified packaging.
Airlines are starting to allow passengers to carry lithium batteries in their luggage, provided that they comply with certain restrictions. These include the FAA’s safety alert that asks airlines to perform risk assessments on lithium batteries as cargo. This is an effort to prevent the catastrophic aircraft loss caused by lithium battery fires and explosions, which can result in thermal runaway. The FAA’s guidelines also address the need for improved battery safety systems and suppression capabilities. This includes a battery’s ability to control internal pressures and temperatures, as well as its external protection circuits.
Longer Lifespan
Today’s lithium batteries have better energy density, allowing more power to be packed into smaller sizes. This translates to smaller, lighter gadgets and a longer runtime. They are also safer than lead-acid batteries when handled properly. While the flammable electrolyte present in their cells can pose safety risks, a lot of research has made them much safer to use. Some of the latest lithium-ion battery technologies eliminate the flammable electrolyte and reduce the risk of fires and explosions.
Lithium-ion batteries have a longer lifespan than their lead-acid counterparts, but the longevity of these rechargeable lithium batteries depends on a variety of environmental factors, such as cycling and elevated temperatures. For example, cycling a lithium-ion battery to extreme states of charge can diminish the battery’s life span by increasing internal resistance. This happens as a result of side reactions within the battery that trap free lithium ions in the electrodes, reducing the number of Li-ions available to shuttle between them.
Elevated temperatures can also shorten a lithium-ion battery’s lifespan by damaging its electrolyte. This is because the battery’s internal temperature rises when it is dwelling in a full state of charge for an extended period, leading to capacity loss and gas generation. In such cases, trickle charging (charging only a battery to its minimal level of charge) is a better option for prolonging the battery’s life.
Fast Charging
Many people will use a portable lithium battery with their mobile phone, but these batteries are also used in many other devices. As a result, these battery systems must be able to charge rapidly. Fast charging can be done by a combination of techniques. One method involves heating the lithium battery to a temperature that prevents lithium plating and limits the growth of solid electrolyte interphase (SEI). Another method is to provide the battery with a constant current until it reaches its end-of-charge voltage.
Most portable lithium batteries can be charged to about 80% of their capacity in just 30 minutes. After that, the battery’s ability to absorb power declines. This is because the battery has already filled up some of its internal resistance and is unable to take any more current without harming the pack’s performance.
In cold temperatures, this effect is exacerbated. Providing a constant voltage after this point stresses the battery and can accelerate irreversible capacity loss. This is why a good portable battery system will allow the voltage to drop slightly before shutting off. It will still provide a substantial amount of energy for its users. A topping charge is then applied to compensate for the small amount of self-discharge and reduce stress. This is a common practice for many lithium batteries, but it can be difficult to implement with some battery designs.
Minimal Maintenance
While lithium-ion batteries are an impressive advancement, their power density demands special care to reach their full potential. Taking care of them can be as simple as regulating the storage temperature and keeping them dry. However, a deeper understanding of how they function is essential for their longevity and performance.
Lithium batteries are essentially two electrodes: an anode made of Carbon and a cathode made of Cobalt Oxide. These are connected by a electrolyte solution containing lithium ions. During discharge electrons flow from the anode to the cathode where they are bombarded until positively charged. This positive charge makes the cathode attract negatively charged electrons and they are then made to flow through our circuit.
High charging and discharging currents significantly reduce battery cylcle life. Also, extreme Portable lithium-ion battery deep discharges can irreversibly damage a lithium battery causing metallic plating on the inside.
To prevent this from happening, most lithium batteries are designed with protective features that open the battery connection once it reaches the peak cut off voltage, which is typically around 4.2V. Then the charger switches to CV (Constant Voltage) mode where a constant charging voltage is applied with the charge current tapering off as the battery gets closer to a fully charged state. This method greatly improves battery cycle life and lifespan. Battery systems with BMS (Battery Management System) also allow for monitoring the internal cell temperatures and disconnecting the battery if it overheats.
