Solar energy systems are being adopted at unprecedented rates all over the world, as energy prices continue to be volatile and fluctuate. Solar energy systems are being deployed to support base loads, become an alternative energy source, or replace previous energy sources entirely.
At the core of a solar energy system is the flow and conversion of energy between DC (direct current) and AC (alternating current).
Solar panels generate electricity in DC form, which is stored in lithium-ion batteries, which are DC systems. However, most loads (homes, commercial equipment, and the grid) operate on AC power. This means energy is constantly being converted between DC and AC via inverters and converters.
During charging (AC → DC) and discharging (DC → AC), losses occur in the form of heat. Under normal conditions, this heat is managed through system design and cooling. But under stress, such as high ambient temperatures, high charge/discharge rates, or inefficient conversion, heat can accumulate within battery cells faster than it is dissipated.
This is where thermal runaway risk begins. This blog details what thermal runway is and how to prevent it.
A thorough understanding of thermal runaway is one of your very best defenses in preventing it from affecting your operations and site.
What is Thermal Runway?
Thermal runway is not just a basic kind of burning fire; it is a chain reaction within a battery cell that can be very difficult to put out.
Typical fires burn out with time, but thermal runways do not easily get put out. They keep getting hotter, higher temperatures release more energy, and this release keeps the fire burning, which increases the temperature further; it is a burning loop that is difficult to end. This is why it takes so much water to put out.
Thermal Runways are becoming more prevalent as the use of lithium batteries becomes even more common.
Thermal runaway in batteries is a self-accelerating exothermic process triggered when heat generation within a cell exceeds its ability to dissipate that heat. As internal temperatures rise, key components like the solid electrolyte interphase (SEI), electrolyte, and cathode materials begin to decompose. These reactions release additional heat and, in some cases, flammable gases, further increasing internal pressure and temperature.
When a battery gets hot, instead of cooling down, it keeps getting hotter until it fails, catches fire, or even explodes.
What Temperature Does Thermal Runaway Start At?
Thermal runaway doesn’t happen at a single fixed temperature, but for most lithium-ion batteries:
1. Early risk can begin around 60°C
2. Thermal runaway typically initiates between 60°C and 100°C
3. Severe failure happens when the temperature is above 120°C–150°C
It’s important to note that high ambient temperatures can significantly lower the threshold at which thermal runaway begins.
What Is the Primary Cause of Thermal Runaway?
The primary cause of thermal runaway is excessive heat buildup combined with internal instability.
Common triggers of thermal runway include:
- Overcharging
- Internal short circuits
- Poor battery management
- Physical damage (punctures, crushing)
- High ambient temperatures
- Inadequate cooling or ventilation
In solar installations, prolonged exposure to heat and improper system design can increase the risk of thermal runaway happening.
What Batteries Are Prone to Thermal Runaway?
The batteries most prone to thermal runaway are Lithium-ion batteries with high energy densities, especially those utilizing Nickel Manganese Cobalt (NMC) and Lithium Cobalt Oxide (LCO) chemistries. Another type of battery that is prone to thermal runaway is lithium polymer batteries.
These are widely used in solar and energy storage systems because of their performance, but they require careful management.
Alternatives that are at a lower risk of thermal runways include:
- Lithium Iron Phosphate (LFP) Batteries: These types of batteries are widely considered to be the safest lithium-based chemistry. This is because they have a higher thermal runway threshold (typically >270°) compared to NMC or NCA (Nickel Cobalt Aluminuim Oxide) batteries (<210°C). Lithium Iron Phosphate cells do not release oxygen during decomposition, and this significantly reduces fire risk.
- Sodium-Ion (Na-ion) Batteries: These are a promising, safe alternative, because they use abundant materials and have naturally superior thermal stability compared to lithium-ion batteries. They typically have less violent reactions during a failure.
- Solid State Batteries: These types of batteries replace the flammable liquid electrolyte of conventional lithium-ion batteries with a solid material, acting as a fire break and reducing the risk of overheating and fire.
- Redox Flow Batteries: an example is Vanadium Flow. These types of batteries use large tanks of liquid electrolytes pumped across a membrane, and this removes the risk of traditional thermal runaway. This makes them suitable for large-scale energy storage.
- Zinc-Based Batteries: Examples of these batteries are Zinc-Air, Nickel-Zinc. These types of batteries are naturally safer because of their non-flammable properties. Nickel-Zinc batteries are specifically designed for high-power, safe applications.
- Organic Batteries: These batteries offer one of the lowest environmental and safety risks. They use non-toxic materials, although they typically have lower energy densities.
What Are the Conditions for Thermal Runaway?
Thermal runaway typically happens when multiple risk factors combine; these multiple factors can include:
1. High ambient temperature
2. Overcharging or deep discharging
3. Poor ventilation
4 High charge/discharge rates
5. Mechanical damage
6. Manufacturing defects
In environments with solar energy systems installed, poorly ventilated battery rooms or exposure to direct sunlight can accelerate these conditions.
What Are the Warning Signs of Thermal Runaway?
Early detection is critical in the prevention of battery thermal runaway. Luckily, they can be detected through warning signs. Ignoring these signs can lead to catastrophic failure. Common warning signs of thermal runway include:
1. Rapid or unusual temperature rise
2. Swelling or bulging battery casing
3. Hissing or popping sounds
4. Burning or chemical odors
5. Smoke or gas release
6. Sudden performance drop
What Is the Best Way to Extinguish a Thermal Runaway Fire?
Thermal runaway fires are complicated and need careful and specific handling.
The best ways to extinguish a thermal runaway fire include:
1. Applying large amounts of water to cool the battery and prevent propagation
2. Using Class D fire extinguishers where applicable
3. Containing the fire with sand or fire-resistant materials
Note that even after flames are out, the battery can reignite, so continuous cooling is important.
How to Prevent Thermal Runway in Batteries
1. Store Lithium Batteries Safely
Safe storage is key to prevention. Lithium batteries should be stored in cool, dry environments, away from direct sunlight and heat sources. It should be stored in well-ventilated areas away from flammable material in fire-resistant containers. For solar installations, dedicated battery rooms with temperature monitoring are highly recommended.
2. Observe the 40 to 80 Rule for Batteries
What is the 40 to 80 rule for batteries? It is a simple, effective guideline that entails keeping a battery charge between 40% and 80% for daily use. This helps reduce heat generation, extend battery lifespan, and lower the risk of thermal stress and runway.
3. Avoid Overcharging or Overloading Batteries
Stick to recommended usage limits to reduce stress on battery cells, avoid overcharging or overloading batteries to prevent thermal runway.
4. Conduct Checks Regularly for Warning Signs
Conduct regular checks, so you can spot warning signs early; check for swelling, leaks, or unusual performance changes.
5. Design Systems for Safety
Proper spacing, shielding, and thermal management in system design can significantly reduce the risks of thermal runway in batteries.
6. Ensure Proper Cooling and Ventilation
Make sure to provide conditions for proper cooling and ventilation. Good airflow prevents heat accumulation, especially in enclosed solar battery setups.
7. Use an Advanced Battery Management System (BMS) or Energy Management System
These systems can help ensure safe charging and discharging, as well as anomalies that have to do with overloading, before they become huge disruptions. These systems can also initiate automatic shutdown during unsafe conditions.
8. Monitor Temperature, Including Ambient Conditions
Ambient temperature plays a critical role in heat buildup. Monitoring it helps systems adjust before overheating occurs. Energy management systems like Pai Enterprise help operators and facility managers track/see ambient conditions in real time. They can also see humidity levels and track humidity trends over time.
Prevent Thermal Runway With Pai Enterprise
Thermal Runways are very dangerous, and operational teams should be proactive about preventing them.
With Pai Enterprise, operators can:
- Monitor ambient temperature and humidity in real time
- Track environmental trends across sites
- Detect early warning conditions before escalation
- Perform sizing optimization checks to avoid system overloading
- Gain actionable insights for safer battery operation
By combining intelligent monitoring with operational control, Pai Enterprise helps operators prevent thermal runways and detect early warning signs of thermal runways faster before they become critical failures.
Contact the sales team to book a free walk-through demo with our energy management experts to see how Pai Enterprise can seamlessly help you prevent thermal runaway.