Heating Solutions for Rechargeable Lithium-ion Batteries

“At cold temperatures, the efficiency of batteries drops considerably, and the battery life shortens. DBK’s heating solutions facilitate optimal thermal conditions for all batteries in challenging weather conditions improving performance with prolonged battery life.”

Thermal Management in Batteries

The capacity, performance, and service life of rechargeable batteries are essential for the market success of battery-powered solutions. For all kinds of applications – such as Battery Electric Vehicles (BEV), Electric Bikes or Scooters, Solar powered Solutions, Off-grid Power Supply Systems, and more – the integration of the battery into the overall system is the key.

In general, batteries are classified by their chemical composition. The most common types of batteries are lithium-, lead-, and nickel-based systems. Lithium-ion batteries are the battery of choice for portable devices and electric powertrains due to their high cycle stability during charging or discharging and high power density.

To perform well in the final application, the battery's temperature plays a vital role while operating, i.e., during its charging and discharging cycles. The optimum operating temperature of Lithium-ion batteries lies between 15 and 35 °C. When operated at temperatures lower than 15 °C, the battery gets automatically heated up at the expense of stored electrical energy. This is because of the increased internal cell resistance at cold temperatures, which leads to long heat-up times. As a result, the battery gets permanently deteriorates in the process.

If it’s too cold, the entire operating performance and battery life are inhibited - a shortfall that cannot be made up in the course of time. The same counts for hot summer days when the battery needs to be cooled down. For operating a Li-ion battery Outside the ideal temperature range (15-35 °C), proper and effective thermal management is required to improve efficiency and avoid permanent damage.

Requirements for Battery Heating

DBK offers battery heating solutions applicable in various sectors, such as:

Battery Electric Vehicles (BEV)
E-Bikes, E-Scooters
BEV charging stations
Solar street lamps
Aerospace and Defense sector equipment
Off-grid power supply systems in offshore or onshore process plants
Remote Monitoring and Control of skids and more

All these applications have one thing in common: their rechargeable batteries are exposed to fluctuating weather conditions. At cold temperatures, the efficiency of these batteries drops considerably, and their battery life shortens. DBK’s heating solutions facilitate optimal thermal conditions for all batteries in challenging weather conditions improving performance with prolonged battery life.

Some of the most common requirements when it comes to battery heating are:

Bring the battery from an initial to a final temperature in a specific heating time. The final temperature refers to the temperature at which the charging or discharging process can be re-initiated in the battery. The initial temperature is the lowest temperature to which the battery is exposed.

The heater should consume a specific power from the battery for the entire heating process, calculated based on thermal analysis of the whole system. Consequently, the voltage and maximum current are defined values for the heater.
The maximum heater surface temperature is also predefined - the value usually coincides with power dissipation and other thermal properties within the battery system.
The heater requires a self-regulating PTC behavior, reducing current flow after reaching the needed heater surface temperature, thereby ensuring high safety.
The heater needs to be flexible, ideally in the form of a flexible film heater, so that it can be flexed according to the surface of the battery case and folded along curves or edges.
The heater usually requires a specific electrical connection or termination.
Uniform heating of the entire battery unit is a must.

Heating Solutions for Lithium-ion Batteries

Each application is unique, so each heater is designed for a specific battery. Also, our experience in this regard shows that PTC heating technology, particularly, has proven successful in this field. PTC heating films provide high-density uniform power dissipation to the battery, and its electrical properties can be easily customized as per requirements:

Voltage up to 230 V DC, depending on the desired power dissipation needed in the system - ideally, it coincides with the battery voltage rating.
High current carrying silver or copper electrical contacts for uniform heating and maximum heater safety.
Heater film size up to 970 x 650 mm.
Wide range of temperature-withstanding substrate materials with the possibility of single or double-side adhesive coating.
Wide range of wire terminations with custom cable length on demand.
Integration of temperature switch for added safety.

Example specification:

Parameters	Battery	Heater
Voltage	24V-30V DC	24V-30V DC
Current		5A Max
Power	1.9 kWh storage	80 W consumption
Physical	35x360x70 mm cuboid shape battery pack inside a battery case	350x790 mm flat and flexible sheet with 2 mm thickness between battery pack and case
Thermal	Heat battery from -20 °C to +5 °C in 2 hours	Max 60 °C surface temperature