Meaning
Electrochemical battery degradation processes occur in lithium thionyl chloride cells when high-current demands accelerate the breakdown of the protective passivation layer and temporarily drop the cell voltage below the operating threshold. This LiSOCl2 pulse current depletion is caused by the sudden demand of wireless transmissions, which draw more current than the chemical cell can supply without a buffer capacitor. The resulting voltage dip can cause the microcontroller to reset, interrupting the telemetry transmission.
Chemical Action
The passivation layer is a lithium chloride crystal layer that forms on the lithium anode, preventing self-discharge during storage. When a wireless module activates and draws a high pulse current, this layer must be cracked or dissolved to allow ion flow. If the current is drawn too quickly, the cell voltage drops before the chemical reaction can catch up.
Hardware Mitigation
Design engineers use supercapacitors or hybrid layers in parallel with the battery to handle these high-current spikes. The battery slowly charges the capacitor, which then supplies the burst of energy needed for the wireless transmission. This hybrid configuration protects the battery from excessive depletion and prevents premature shutdown.
System Evaluation
Testing of these systems requires measuring the voltage response under simulated transmission loads at low temperatures. Lower temperatures slow down the chemical activity, increasing the severity of this voltage drop. Monitoring these profiles ensures the device remains reliable over its entire operating lifetime.
