In extreme conditions, one of the most important things to have is a reliable power source. If you want to know what battery is best for your situation, you should first know how cold weather affects them. Batteries are very sensitive to frequent temperature changes and certain weather conditions and it affects battery life, hence it is important to design effective battery thermal management systems to enhance heat dissipation and to meet the requirements such as high power, fast charging rates, and improved performance have been developed and implemented. These rapid changes of the batteries had to be monitored carefully and managed to avoid safety and thermal related issues. So, in conclusion Thermal management in an electric vehicle is important to extend the life of the battery in extreme weather conditions.
Using Lithium Batteries in Cold Weather:
Off-grid living can become treacherous when the temperatures drop below freezing, and you want to know that you have your necessities covered.
Lead-acid batteries tend to have a lower performance rate than their lithium counterpart. This makes lithium batteries a top power source for anyone wanting to explore places where the temperatures drop to frigid conditions. The damage to the battery when charging at colder temperatures is proportional to the charging rate. Charging at a much slower rate can reduce the damage, but this is rarely a practical solution. Temperatures below the 0°C mark will reduce both efficiency and usable capacity of lithium batteries but still operate with very little loss providing 95-98% of their capacity.
When temps fall between 0°C and -10°C,batteries cannot be charged at higher than 1C. When temps fall between -10°C and-20°C, batteries cannot be charged at higher than .05C. At approximately -30°C,battery Ah capacity drops to 50%. At freezing (below -30°C), capacity is reduced by20%. These charging rates will definitely increase charging duration and complicate the entire process. When charging at above-freezing temperatures, the lithium ions inside the battery are soaked up as in a sponge by the porous graphite that makes up the anode, the negative terminal of the battery.
Below freezing, however, the lithium ions aren’t efficiently captured by the anode. Instead, many lithium ions coat the surface of the anode, a process called lithium plating, which means there’s less lithium available to cause the flow of electricity and the battery’s capacity drops. Charging below freezing at an inappropriate charge rate, also causes the battery to become less mechanically stable and more prone to sudden failure. Unless you're BMS communicates with your charger, and the charger has the ability to react to the data provided, this can be difficult to do. If you do charge below freezing temperatures, you must make sure the charge current is 5-10% of the capacity of the battery.
Wide temperature variations
Battery charging voltage also changes with temperature. It will vary from about 2.74volts per cell at -40°C to 2.3 volts per cell at 50°C. This is why you should have temperature compensation on your battery charger or charge control if your batteries are outside and/or subject to wide temperature variations.
We have seeing the growing demand for low-temperature (<–40°C) battery from specific field, such as high-altitude aircrafts, polar expedition, some military equipment and so on.
Meanwhile, the frequent occurrence of extreme weather, such as the recent polar vortex sweeping across half northern hemisphere, incurred many concerns on reduced range of battery-packs as well as reduced durability of battery in many other electronics or electric tools, and it also promotes the increasing requirement on battery performance under ultra-low temperature. The origin of the electrochemical performance deterioration at low temperature has been revealed as the following:
- the electrolyte becomes more viscous or even freezing, worsening the ion mobility and electrode wettability
- the charge transfer within the electrode becomes much more difficult due to the intrinsic grain-boundary resistance and the slow metal-ion diffusion in in organic lattice
- the solid electrolyte interface (SEI) becomes less permeable to metal-ion
- the metal deposition reaction becomes very problematic. These factors collectively lead to the kinetics fading and intertwined impacts make the issue harder to solve
To test our model using thermal analysis for batteries operating in severe weather conditions such as -40°C, following steps have been performed and results are shown:
- Set the Testing Parameters:
• Defining the specific aspects of thermal performance, considering the extreme low temperature (-40°C), we have Identified the critical temperature limits or performance criteria that the batteries must meet in these severe weather conditions.
- Computational Modeling:
• Use thermal analysis software capable of simulating the battery's thermal behavior under extreme cold conditions, a detailed virtual model of the battery system is created, considering its geometry, materials, and internal components and the model accurately representing the physical characteristics of the batteries is ensured.
• The boundary conditions, including the ambient temperature set to-40°C, heat generation rates, thermal conductivity, and specific heat capacities of the materials involved are defined and simulations have been performed.
- Experimental Testing (Optional Method):
• Consider conducting experimental testing in cold chamber facilities to validate the results obtained from the computational modelling using thermocouples or other temperature measurement devices to monitor the battery's temperature during the tests and evaluate their performance, capacity, and stability
• Compare the experimental results with the simulation results to validate the accuracy of the computational model.