The current flowing through the nickel foil forms a circuit within the battery, generating a significant quantity of ohmic heat, thereby quickly heating the battery's core.
In self-heating systems, a larger preheating current may result in overdischarge of the battery pack and damage the battery. Since this system can achieve a high heating rate using a relatively small current, it hardly damages the batteries. 3.2. Influence of the preheating system on battery performance 3.2.1.
The system can preheat the battery safely in the capacity range of 20%–100%. When the battery pack is set in −20 °C, the effective electric energy can be increased by 550% after preheating. An energy conversion model is also built to measure the relationship between the energy improvement of battery and the energy consumption by preheating.
This self-preheating system shows a high heating rate of 17.14 °C/min and excellent temperature uniformity (temperature difference of 3.58 °C). The system can preheat the battery safely in the capacity range of 20%–100%. When the battery pack is set in −20 °C, the effective electric energy can be increased by 550% after preheating.
Why is it important to preheat power batteries quickly and uniformly?
The growth of lithium dendrites will impale the diaphragm, resulting in a short circuit inside the battery, which promotes the thermal runaway (TR) risk. Hence, it is essential to preheat power batteries rapidly and uniformly in extremely low-temperature climates.
Power of batteries preheated to different temperatures at 0.5C (a), 1C (b), and 2C (c) respectively. The average temperature of batteries preheated to different temperatures at 0.5C (d), 1C (e), and 2C (f), respectively. However, the effect of preheating improved with an increase in the discharge rate of the battery pack.
Can a self-preheating system preheat a battery pack?
Owing to small energy consumption and preheat current during preheating, this self-preheating system could still preheat the battery pack from −10 °C to 20 °C even at 0.2 SOC. As shown in Fig. 5 (c), the battery pack was preheated from −10 °C to 20 °C in 180 s, with an increase of the voltage of the battery pack from 14.7 V to 19 V.