Battery cooling is usually framed as a problem of removing heat, and for the most part it is. Charging and discharging generate heat, and packs need active or passive cooling to stay within a safe operating window. But cooling too aggressively carries its own risk, one that is easy to overlook until it causes a fault.
The other side of battery cooling: overcooling
If a pack is cooled below the surrounding ambient temperature, it can dip below the dew point, the temperature at which air can no longer hold its moisture and that moisture condenses onto cooler surfaces instead. Inside a battery enclosure, that condensation can settle on terminals and lead to shorting or corrosion, turning a cooling system meant to protect the pack into a contributor to failure. Metis Engineering’s Cell Guard sensor monitors dew point and humidity directly, giving a battery cooling strategy a way to see this risk coming rather than discovering it after the fact.
Feeding cooling control loops with better data
Cell Guard’s dew point and humidity readings can be used as an input into a pack’s thermal management system, alongside the temperature data a battery management system already relies on. That combination allows a cooling strategy to keep the pack within a safe band on both fronts, warm enough to avoid condensation risk and cool enough to avoid degradation or thermal events, rather than optimising for temperature alone.
Liquid cooling and the condensation question
Liquid cooling systems, which actively pump a coolant around or between cells, are increasingly common in higher power battery packs precisely because they remove heat more effectively than passive approaches such as heat sinks or phase change materials. That effectiveness is exactly what makes the overcooling and condensation risk more relevant, not less. A liquid cooling loop that runs colder than necessary can push surfaces inside the enclosure below the dew point even while the cells themselves remain within a safe temperature range, which is why dew point monitoring matters as much in advanced liquid cooled designs as it does in simpler air cooled packs.
Cooling and thermal runaway prevention work together
Battery cooling and thermal runaway prevention are often treated as separate systems, but Cell Guard links them directly. The sensor can also trigger the process that cuts the circuit to a battery pack, giving it the chance to cool down before an emerging issue develops into thermal runaway. Seen this way, a cooling strategy informed by dew point, humidity and VOC data is not just about comfort or efficiency, it is part of the pack’s safety architecture.
This is particularly relevant for second life battery deployments, where packs built from repurposed EV cells are asked to perform reliably in a new static energy storage role despite an unknown history of wear. A cooling and monitoring strategy that can account for that uncertainty, rather than assuming the pack behaves exactly as it did when new, gives operators a more realistic basis for managing risk over the pack’s second working life.
Logging data for diagnostics, not just control
Beyond driving the cooling system in real time, Cell Guard’s continuous stream of pressure, humidity, dew point and VOC data provides a record that engineers can look back on. If a pack develops a fault months after installation, that logged history can help distinguish a genuine cell issue from a cooling system that has been running slightly too aggressively for the conditions it is operating in, which is a much faster route to a fix than starting an investigation from scratch.
Practical fit for battery cooling architectures
Cell Guard’s compact CAN based form factor, configurable bus speed and address, and supplied DBC file make it straightforward to integrate into liquid cooled or air cooled pack designs across electric vehicles and static energy storage systems alike. Its small size and mass mean it can sit close to the cells it is protecting without adding meaningful weight or complexity to the pack.
Parla con Metis Engineering
If your battery cooling strategy currently relies on temperature data alone, Metis Engineering can talk through how Cell Guard’s dew point, humidity and VOC monitoring adds the missing layer of insight.
