With temperature rising across the nation this summer, we have been seeing an uptick in the number of emergency situations for thermal runaways. We’ve all seen the images of cellphones and portable batteries catching fire. Imagine that happening on a larger scale in an industrial setting.
What is Thermal Runaway:
In simplest terms, thermal runaway begins when the heat generated within a battery exceeds the amount of heat that is dissipated to its surroundings. If the cause of excessive heat creation is not remedied, the condition will worsen. Internal battery temperature will continue to rise, causing battery current to rise, creating a domino effect. The rise in temperature in a single battery will begin to affect other batteries in close proximity, and the pattern will continue, thus the term “runaway.”
Responding to Thermal Runaway:
If caught in time, a thermal runaway damages a single cell. If not caught, this situation can quickly escalate leading to fires and explosions. Some things to look at to prevent a thermal runaway from happening:
· MAKE SURE THE AC IS WORKING – Batteries are fundamentally a chemical reaction. Higher temperatures means faster chemical reactions. Faster reactions means more heat is being generated.
· LOWER THE CHARGING CURRENT – As batteries heat up, the internal resistance changes meaning more current to flow through the battery for the same voltage applied. In a normal situation, a properly maintained battery will be drawing less than 1 amp.
· TOP UP THE FLUID LEVELS – If possible, make sure the cells are topped up with liquid. Some styles of batteries cannot be filled. In that situation, your best bet is to lower the temperature and reduce the charging current.
· ISOLATE THE PROBLEM CELL – Using thermal imaging can identify which cells are causing the problem. The problem cell can then be isolated before causing the rest of the string to fail. If you cannot isolate the individual cell or the thermal runaway has spread to other cells in the string, remove the power and cool the batteries.
- CALL YOUR BATTERY EXPERTS – Contact Power Storage Solutions Contact us today
Since all batteries off-gas some volume of hydrogen, you need to be aware of the potential of an oxygen deficient environment. If you are not comfortable dealing with a thermal runaway situation, the experts at Power Storage Solutions are here to help.
Preventing Thermal Runaway:
A properly designed and implemented PM program for your battery back-ups can help identify and correct any deficiencies before they become catastrophic failures.
So, what do you look for with a regular PM program?
- Charger voltage – Is the charger voltage too high, over 2.4V per cell? Is the charger temperature compensated?
- Shorted Cells – Has there been a change in the internal impedance values from the last PM? Are all the cells in the string moving the same direction, or is there one that is standing out? In VRLA batteries, impedance is a surrogate for electrolyte level.
- Individual Cell Voltages – Have the cells been fully discharged and not charged properly? Where are the cells at with regards to their state of charge? Are the individual voltages even across the string?
- Damaged Cells – Are there signs of physical damage or corrosion on the battery terminals, posts or jars themselves? Can the damages be corrected, or should the cells be replaced?
- Room Cooling/Ventilation – In certain regions, temperatures inside battery rooms or enclosures can reach over 120°F. Can the ventilation/AC system keep up? Is there enough ventilation to prevent buildup of dangerous levels of hydrogen gas?
Preventive Maintenance is essential to the reliability of your plan. Request a Solution today for your company’s peace of mind. We will help put your plan together.
For more technical information – IEEE Abstract – B. Ashdown and N. Tullius, “Prevention of thermal runaway in VRLA batteries,” INTELEC – Twentieth International Telecommunications Energy Conference (Cat. No.98CH36263), 1998, pp. 532-535, doi: 10.1109/INTLEC.1998.793589.
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