With the continuous development of lithium battery technology, Custom lithium battery pack is widely used in many fields such as consumer electronics, electric bicycles and other mobile products, electric vehicles and energy storage solutions.

However, if there is insufficient safety awareness and improper handling during use, storage, disposal, etc.,  Custom lithium battery pack will become a “ticking time bomb.”

Generally speaking, the safety problems of lithium-ion batteries mainly manifest themselves as combustion or even explosion.

Lithium batteries are both flammable materials and sources of ignition. Once collision, extrusion, overcharge, short circuit, etc. occur, it can easily cause fires, explosions and other safety accidents, resulting in casualties.

The root cause of these problems lies in thermal runaway inside the battery.

After the thermal runaway of the lithium-ion battery, the decomposed flammable gas mixes with air to form an explosive mixed gas. When encountering the high-temperature particles ejected from the lithium battery, deflagration will occur in a local space, resulting in an explosion sound in the early stages of a fire.

The characteristics of custom lithium battery pack fires: fast ignition, long duration, high combustion temperature, difficulty in extinguishing, spontaneous combustion or even explosion for a long time.

Causes of lithium battery fire and explosion

Lithium batteries mainly rely on the movement of lithium ions between the positive and negative electrodes to achieve the charging and discharging process. From a principle point of view, the main factors that cause lithium battery explosions are overcharging and short circuits.

Overcharging mainly occurs during the charging process of lithium batteries. Due to the resistance of the battery, the battery will accumulate a large amount of heat during the charging process. The protection device in lithium batteries can provide a certain degree of protection against overcharge by detecting voltage.

However, when the overcharge time is too long and the voltage continues to be too high, dendritic short circuits are likely to occur inside the lithium-ion battery, causing the temperature and pressure of the lithium battery to continue to rise, resulting in the risk of explosion and fire.

Short circuit mainly occurs during the use of lithium batteries. When the lithium battery is in use, its own temperature will continue to rise, and the battery also maintains normal heat dissipation.

If the battery temperature is too high due to external factors, it will easily cause damage to the battery separator and cause a short circuit, which will cause excessive internal heat accumulation, trigger a chain chemical reaction, and cause the battery to explode and burn.

According to statistics from the emergency management department, in the first quarter of 2023 alone, the spontaneous combustion rate of new energy vehicles increased by 32%, with an average of 8 new energy vehicles catching fire (including spontaneous combustion) every day.

Lithium battery safety tips

Purchase regular and qualified lithium battery products and tools.

When lithium battery products and tools are not in use, try to remove the batteries and store them separately.

Li ion customized battery packs should avoid being stored in humid, high-temperature locations, and should be kept away from flammable and combustible materials.

After the lithium battery is fully charged, the power supply should be disconnected promptly and do not be charged continuously for a long time.

Do not squeeze or drop lithium battery products and tools during daily use.

Lithium battery fire fighting tools

When a lithium battery catches fire, a dry powder fire extinguisher can only extinguish the surrounding flames, but cannot effectively prevent the lithium battery from thermal runaway. Water or water-based fire extinguishers are the first choice for emergency response to lithium battery fires.

The basic principle of dry powder fire extinguisher is chemical suppression. It can generally extinguish solid fires, and can also extinguish incipient fires of flammable liquids, combustible gases and electrical equipment. Although dry powder fire extinguishers can extinguish open flames under initial circumstances, dry powder fire extinguishers cannot reduce the temperature inside lithium batteries. At this time, the internal temperature of the lithium battery is still very high, and the internal chemical reaction continues. After the heat is accumulated, it is easy to reignite or even explode.

Water/water-based fire extinguishers can not only eliminate open flames, but also have a certain cooling effect, so they are the first choice for emergency treatment of lithium battery pack fires.

Key points: The method of extinguishing fires with water/water-based fire extinguishers is suitable for lithium batteries with relatively low voltage, because there is no risk of electric shock. If a lithium battery plugged into AC catches fire, be sure to unplug the power before watering. Otherwise, there will not only be a risk of electric shock, but also a secondary fire caused by the electrolysis of water by 220V AC.

Lithium battery fire fighting

1. Disconnect or remove external power from the fire equipment.
2. Immediately and continuously saturate the electronic device on fire with water or other non-flammable liquid to lower the temperature of the lithium battery cell core, block heat dissipation, and prevent adjacent battery cells from catching fire.
3. If the device was previously connected to an electrical outlet, unplug the power from all remaining electrical outlets until the system is confirmed to be fault-free.
4. Do not attempt to move burning or smoking electronic equipment to prevent serious personal injury.
5. Do not cover or attempt to lower the temperature with ice. This method of isolating the equipment will prevent the heat from being dissipated in a short period of time, which in turn increases the risk.

If you have any question, please feel free to contact us:

• Name: Dawn Zeng (Director)
• E-mail address: sales@himaxelectronics.com

Li ion customized battery packs have the advantages of high voltage, large specific energy, repeated charge and discharge, no memory effect, and no pollution, so they are more suitable for use as backup power sources in fire-fighting equipment.

Fire power supply is an important part of fire equipment. For a fire protection system, if there is no reliable fire power supply, the fire protection equipment cannot be started, the fire shutters and fire doors in the fire protection zone cannot be in place, the smoke exhaust system, fire elevators, fire lighting, etc. cannot work properly. Therefore, reliable fire power supply is the guarantee for the normal operation of fire protection equipment and provides power for the operation of all fire protection facilities in the building.

Usually, we will first choose 18650 lithium ion battery pack and 26650 li ion battery pack, also LiFePO4 32700 battery pack to make fire power supplies. Because these custom lithium battery pack have a wide range of capacity options and are small in size, they can be easily made into battery packs of different sizes to adapt to different fire-fighting facilities.

We have already manufactured different kind of li ion customized battery packs for our customer, like 18650 battery pack 14.8V 17.5Ah, LiFePO4 12.8V 18Ah battery.

HIMAX can make all kinds of custom lithium battery pack and 12v Lead Acid Replacement Battery for our customers. We have full of confidence to meet your quality level. Looking forward to build a long term business with you and we wait for your kind respond

Contact Himax now to unlock your exclusive battery customization options, Himax offers a wide range of options and flexible customization services to meet the needs of different users.

If you have any question, please feel free to contact us:

• Name: Dawn Zeng (Director)
• E-mail address: sales@himaxelectronics.com

Are lithium batteries safe? Generally speaking, the problems of whether lithium batteries are safe are manifested as burning or even explosion. The root cause of these problems is the thermal runaway inside the battery. In addition, some external factors may also affect li ion customized battery packs and cause concerns about whether lithium batteries are safe, such as overcharging, fire, extrusion, puncture, short circuit, etc.

According to statistics, 68% of electric vehicle li ion customized battery packs fire accidents over the years were caused by internal or external short circuits, 15% were caused by charging and discharging, 7% were caused by accidental startup of equipment, and other reasons caused 10%.

From the perspective of the cause of the fire, electrical faults, and spontaneous combustion are the leading causes of fires in electric vehicles, while overcharging, battery cell failures, and short circuits in electrical circuits are the root causes of fires and bring the concern that our lithium batteries are safe.

Which battery is the safest?

So, are li ion customized battery packs safe? The safety performance of lithium iron phosphate batteries will be higher than that of ternary lithium batteries. This is mainly because the heat resistance of lithium iron phosphate batteries is relatively good, and the thermal runaway temperature can reach more than 800℃.

The battery catches fire primarily due to factors such as short circuits, impact, and overcharging, which drives the concern of whether lithium batteries are safe. When the current passes through, a large amount of heat will appear in the overpotential and ohmic polarization, which will locally heat the battery to the temperature of the thermal decomposition of the cathode. The heat caused the battery to explode and catch fire.

The ignition point of the ternary lithium battery is only 200℃, and the ignition point of the lithium iron phosphate battery is 800℃. After an accident, the collision extrusion temperature can easily exceed the critical value.

In other words, lithium iron phosphate batteries will not spontaneously ignite if they do not reach 800℃. The ternary lithium battery is different. The thermal runaway temperature is basically around 200℃. Looking at the spontaneous combustion incidents of new energy vehicles, most of them are ternary lithium batteries. Therefore, for areas of hot weather, the risk of spontaneous combustion of ternary lithium batteries will be higher.

If you have any question, please feel free to contact us:

• Name: Dawn Zeng (Director)
• E-mail address: sales@himaxelectronics.com

The use of li ion customized battery packs in low battery temperature environments is limited. In addition to the serious decline in discharge capacity, lithium batteries cannot be charged at low battery temperature. When charging at low battery temperature, the intercalation and lithium plating reactions of lithium ions on the graphite electrode of the battery exist simultaneously and compete with each other.

The diffusion of lithium ions in graphite is inhibited under low battery temperature conditions, and the conductivity of the electrolyte decreases, resulting in a decrease in the intercalation rate and the lithium plating reaction is more likely to occur on the graphite surface. The main reasons for the decline in the life of lithium-ion batteries when they are used at low battery temperature are the increase in internal impedance and the loss of capacity due to the precipitation of lithium ions.

1.Effect of low battery temperature on battery discharge capacity

Capacity is one of the most important parameters of lithium batteries, and its size varies with temperature. For AGM replacement battery, the charge end voltage is 3.65±0.05V, and the discharge end voltage is 2±0.05V. The two curves are the temperature capacity curves obtained by discharging the battery at different temperatures at 0.1C and 0.3C respectively.

2.Effect of low battery temperature on battery internal resistance

The relationship between li ion customized battery packs temperature and resistance is shown in the figure below. Different curves represent different charge levels of the battery itself. Under any charge, the internal resistance of the battery increases significantly as the temperature decreases. The lower the charge, the greater the internal resistance, and this trend remains unchanged as the temperature changes.

At low battery temperature, in the cathode and anode materials, the diffusion and movement ability of charged ions becomes poor, and it becomes difficult to pass through the passivation film between the electrode and the electrolyte. The speed of transfer in the electrolyte is also reduced, and a lot of heat is additionally generated during the transfer.

After lithium ions reach the anode, the diffusion inside the anode material also becomes unsmooth. During the whole process, the movement of charged ions becomes very difficult. From the outside, it means that the internal resistance of the battery cell has increased.

3. Effect of low battery temperature on battery charge and discharge efficiency

The lower curve is the curve of charging efficiency changing with temperature. We can observe that the charging efficiency at -20°C is only 65% of that at 15°C.

The low battery temperature brings about the changes in the various electrochemical performances described above, and the internal resistance increases significantly. During the discharge process, a large amount of electric energy is consumed on the internal resistance to generate heat.

4. Internal side reactions of lithium-ion batteries at low battery temperatures

The performance of li ion customized battery packs degrades severely at low battery temperatures, and some side reactions will occur during the charging and discharging process of lithium-ion batteries. These side reactions are mainly the irreversible reaction between lithium ions and the electrolyte, which will cause the capacity of the lithium battery to decline and further deteriorate the battery performance.

The consumption of conductive active material causes capacity fading. Considering the potentials of the cathode and anode in the battery, these side reactions are more likely to occur on the anode side than the cathode side. Because the potential of the anode material is much lower than that of the cathode material, the deposits of side reactions of ions and electrolyte solvents are deposited on the electrode surface, forming an SEI film. The impedance of the SEI film is one of the factors that cause the overpotential of the anode reaction.

When the battery is further cycled and aged, due to the continuous insertion and extraction of lithium ions on the anode during continuous cycles, the expansion and contraction of the electrode caused by the continuous cycle will cause the SEI film to rupture. The cracks after the rupture of the SEI film provide a direct contact channel between the electrolyte and the electrode, thereby forming a new SEI film to fill the crack and increase the thickness of the SEI film.

These reaction processes are constantly repeated as the battery is continuously charged and discharged, so that lithium ions are continuously reduced in the reaction, resulting in a decline in the discharge capacity of the lithium-ion battery.

During charging, deposits form on the surface of the active material, increasing the electrical resistance. The effective surface area of the active particles is reduced and the ionic resistance is increased. The usable capacity and energy of lithium batteries decline simultaneously. Lithium batteries are more prone to side reactions during charging.

At the beginning of lithium battery charging, lithium ions move to the anode through the electrolyte, so the potential difference between the electrode and the electrolyte decreases, making it easier for lithium ions to undergo irreversible side reactions with the substances in the electrolyte. The different electrode materials of lithium-ion batteries have different relationship curves between the potential and the lithium intercalation concentration fraction of the electrode material.

Lithium battery low temperature preheating technology

Faced with the limited use of lithium batteries at low battery temperature, the technicians found a countermeasure to charge and preheat. Although it is an expedient measure, it has a significant effect on improving the discharge capacity and long-term life of lithium batteries.

Before charging or using a lithium battery in a low battery temperature environment, the battery must be preheated. The way the battery management system (BMS) heats the battery can be roughly divided into two categories: external heating and internal heating.

Compared with external heating methods, internal heating avoids long-path heat conduction and the formation of local hot spots close to the heating device. Therefore, internal heating can heat the battery more uniformly for better heating with higher efficiency and is easier to implement.

At present, most of the research on the internal AC preheating scheme focuses on the heating speed and efficiency, and there is little clear consideration of the heating strategy to prevent the occurrence of side reactions such as lithium deposition.

In order to prevent the generation of lithium deposition during the preheating process, it is necessary for the BMS to estimate and control the conditions of lithium deposition in real time. A model-based controlled battery heating technique at low battery temperature is required to achieve the above functions.

With the development of new energy, the use of power li ion customized battery packs is also increasing day by day. The use of lithium batteries at low battery temperature urgently needs to solve the problem of battery warm-up. This is a field that is very close to practical applications. In addition, AC heating, mobilizing electrochemical substances to generate movement, and the impact on battery life have not yet been seen. It is also a problem worthy of continuous attention.

If you have any question, please feel free to contact us:

• Name: Dawn Zeng (Director)
• E-mail address: sales@himaxelectronics.com

With the development of science and technology, batteries have become an indispensable part of our daily life. Among them, 18650 Li-ion battery pack, as a kind of high energy density and long life battery, is widely used in electronic equipment, electric vehicles, aviation and other fields. This article will introduce the principle, characteristics, applications and safety precautions of 18650 lithium-ion battery pack.

First, the working principle of 18650 lithium-ion battery packs

18650 lithium-ion battery pack is composed of positive pole, negative pole, diaphragm, electrolyte and shell. Its working principle is

• when the external circuit through the current, the lithium atoms on the positive electrode is transferred to the negative electrode, forming lithium ions, thus realizing the mutual conversion of electric energy and chemical energy. This process is controlled by the interaction between the lithium ions and the electrolyte, and the lithium ions migrate between the positive and negative electrodes, thus maintaining the voltage balance of the battery.

Second, the characteristics of 18650 lithium-ion battery packs

• 18650 lithium-ion battery pack has the advantages of high energy density, long life and no memory effect. Its energy density is more than three times that of traditional lead-acid batteries, so it can provide higher power in a smaller volume. Meanwhile, due to its no memory effect, users can charge it anywhere and anytime, which is convenient. In addition, it also has the advantages of good high temperature performance, light weight, easy mass production.

Third, 18650 lithium-ion battery pack application areas

• 18650 battery pack has a wide range of applications, including electronic equipment, electric vehicles, aviation and so on. In terms of electronic equipment, it is widely used in camcorders, digital cameras, tablet PCs and other fields to provide reliable energy security. In the field of electric vehicles, it replaces lead-acid batteries and improves the range and performance of electric vehicles. In the field of aviation, it is widely used in airplanes, providing reliable energy security for airplanes.

Fourth, safety precautions

Although 18650 lithium-ion battery packs have many advantages, it is still necessary to pay attention to safety in the process of use. First, use lithium-ion battery packs produced by regular manufacturers, avoid using low-quality or counterfeit products. Secondly, please do not put the battery in a high temperature environment when charging, high temperature will damage the battery performance. In addition, please do not disassemble, invert or shake the battery during charging to avoid arcing or short-circuiting. Using 18650 Li-ion battery packs in high temperature and high humidity environments may cause safety problems, so it is recommended to use them in a moderate temperature environment.

If you have any question, please feel free to contact us:

• Name: Dawn Zeng (Director)
• E-mail address: sales@himaxelectronics.com