What kind of energy storage battery is suitable for use in high latitude countries or regions and what are the precautions for this kind of battery pack process? Maybe many people who live in Russia, Canada, Iceland, Norway, Sweden, Denmark, and Finland have the above doubts.
The division of latitude is based on the fact that geography experts divide the earth into the southern hemisphere and the northern hemisphere. The equator is 0 degrees, and the South Pole and the north pole are 90 degrees. So it is divided into three equal parts between 0 degrees and 90 degrees. The northern and southern hemispheres add up to a total of six equal parts, one of which is 30 degrees. According to this division method, low latitude, middle latitude, and high latitude are formed.
The winter in high latitudes is long and cold, and the monthly average temperature is below 0 ℃; Summer is short and warm, and the monthly average temperature is above 10 ° C. The annual precipitation is 300 ~ 600mm, and the relative humidity is high. The annual temperature range is large. This area is the source of polar continental air mass with high latitude, long night time in winter, small noon sun altitude angle, snow cover, intense ground radiation cooling, and can not be adjusted by marine air mass.
Due to the relatively low temperature in winter in high latitude countries or regions, can NCM batteries/ lithium titanate batteries/lithium iron phosphate batteries be used?
Different Lithium Battery Type Analysis In Cold Environment
1. NCM Energy Storage Lithium Battery
The temperature characteristic of the NCM low-temperature lithium battery pack is an indicator of battery reliability, and the performance of the battery can also be evaluated by changing the ambient temperature. The low-temperature characteristics of NCM lithium batteries are mainly investigated from the low-temperature discharge characteristics and cycle life. The most important thing of low-temperature batteries is to maintain the fluidity of materials under low-temperature conditions so that lithium ions can shuttle freely between the positive and negative electrodes to realize the charging and discharging of batteries.
At present, NCM lithium battery manufacturers can basically achieve a discharge temperature of -20 °C, with a discharge capacity of more than 50%, and cycle life of about 800 times, which can fully meet the needs of ordinary energy storage systems appliances and power consumption scenarios.
However, in special aerospace, special equipment, and other special products, or in the northern, alpine and other cold environments, NCM lithium battery packs must be able to reach a lower discharge working temperature to meet the harsh service conditions.
2. Lithium titanate battery
Lithium titanate battery is a kind of lithium-ion battery cathode material – lithium titanate, which can form a 2.4V or 1.9V lithium-ion secondary battery with cathode materials such as lithium manganate, NCM material, or lithium iron phosphate. In addition, it can also be used as a positive pole to form a 1.5V lithium secondary battery with metal lithium or lithium alloy negative pole.
Lithium titanate battery has good wide temperature resistance and strong durability. It can be charged and discharged normally from -50 ℃ to 60 ℃. At -20 ° C, the discharge capacity can still reach 76% of that under room temperature. But the cost is extremely high, so seldom people use lithium titanate batteries for energy storage.
3. Lithium iron phosphate battery(LFP Battery)
The working environment of lithium iron phosphate battery is generally -20 ° C to 65 ° C. At -20 ° C, the performance is only 30-50% of normal temperature, and the cycle decay is very rapid. But the cycle life is 3000-6000 times, so the long cycle life is attractive to many household owners.
From the comparison of the -20 ° C discharge performance of the above three lithium batteries, it can be seen that NCM batteries and lithium titanate batteries are more suitable for high latitude areas. But due to the household energy storage batteries are used at home or commercial indoor, the home temperature is normally above -20 ° C, so the lithium iron phosphate battery can also be widely used in the energy storage battery. And the LFP battery’s 3000-6000 long cycle life advantage makes the LFP battery most economical and competitive in altitude countries.
Battery Pack Technology Advantage or Disadvantage
For lithium batteries used in high latitude countries or regions, in addition to the selection of cells, the packing process is also very important, mainly reflected in the series or parallel mode of cells, the connection mode of power lines, and the installation mode of voltage acquisition lines, etc. At present, lithium battery pack processes mainly include laser welding, locking screw, spot welding, soldering, etc.
1. Laser Welding Technology
As a very important process of battery production, it has a great impact on the consistency, stability, and safety of the battery. There are many laser welding parts of the battery, and the process is difficult, so the requirements for the welding process are higher. High efficiency and precision laser welding can greatly improve the safety, reliability, and service life of batteries.
The laser welding equipment is generally 3KW. When welding 1mm thick connecting aluminum sheet, the power is adjusted to 40% – 60% of the total power. When welding, the connecting piece should be in full contact with the end face of the pole of the electric core to prevent gaps. The connecting piece shall be in the H state, which has high strength and is not easy to tear when moving the battery pack.
2. Locking Screw Technology
It is an advanced packing process of lithium battery, which is common in the field of low-speed vehicles and household energy storage. The way of locking the screw makes the lithium battery pack simple, saves the laser welding equipment, and only needs a wrench to realize it. At the same time, it is convenient to disassemble the problematic battery.
3. Soldering Technology
Solder generally refers to the solder alloy of tin-lead or tin silver copper. Under normal circumstances, the melting point of tin is 231.9 ℃. Generally speaking, the melting point of tin bar alloy is lower than that of any of its constituent metals. Take lead solder (tin content 63%, lead content 37%) as an example, the melting point of lead solder is about 183 ℃. The melting point of lead-free solder is about 220 ℃ (tin 99.3%, copper 0.7%).
When soldering tin, it may be necessary to adjust the temperature higher, because the copper-plated aluminum sheets used for series or parallel connection of electric cells need to be soldered with tin at a higher temperature.
4. Tin plague (low temperature)
That is, tin will get sick, mainly because it loses its original characteristics at low temperature, that is, the phenomenon of tin collapsing into powder at low temperature.
Tin has two kinds of crystals. When the temperature is above 13 ℃, it is a bright block of white tin（ β Tin), that can be used as noble decorations or watchcases, wine pots, and teapots. However, if the temperature is lower than 13 ℃, the crystal will gradually crack and begin to transform into its allotrope gray tin（ α Tin), but the transformation speed is very slow. Once the temperature drops to about -33 ℃, the change of crystal disintegration is extreme, and white tin becomes powdery “gray tin”.
When β Tin (density 7.298 g / cm) is converted to α When tin (density 5.846 g / cm) increases by about 20% in volume, it will collapse into powder. The small amount of aluminum, copper, magnesium, manganese, zinc, and other impurities contained in the original tin can accelerate this transformation; However, impurities such as bismuth, lead, antimony, silver, and gold can slow down the transformation, and even inhibit the transformation when the content increases to a certain amount. In order to avoid the occurrence of tin epidemic, the temperature of tin during storage and transportation should not be too low, and tin containers or tin welding containers should not be used in cold areas. Powdered gray tin can be remelted into the white tin.
Based on the above welding methods, it is recommended when lithium batteries pack are produced to be used in high latitude countries and regions, the battery cells can be connected in series or in parallel by laser welding or locking screw, and the voltage acquisition line can be connected by low-power laser welding or locking screw, and the power line is connected by locking screw.
SmartPropel factory production line adopts both laser welding technology and locking screw technology due to different battery pack applications and ensures their energy storage battery for household energy saving and power battery for electric vehicles perform excellently.
Their batteries are available for high-altitude countries, such as Russia, Canada, Iceland, Norway, Sweden, Denmark, and Finland. People in these countries can relax to use lithium batteries even in extreme cold snowy weather.