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Safe as robots – LiFePO4 batteries explained

Article by Michael Trimmer
yellow circuit board with wires and green elements

Batteries have often been an item of concern when it comes to health and safety. Whether it’s the chemicals they are made of, the potential to overheat, or the risk of fire, batteries often get extra risk-assessment-related attention. Thus, understanding the specific advantages and disadvantages of particular types of batteries can be extremely important.

Wise Robotics and Hikrobot paid special attention to these issues when developing the technology behind our flexible automation solutions. We went beyond merely meeting the CE safety baseline, and deliver you equipment fitted with Lithium iron phosphate batteries. Sometimes better known as LiFePO4 batteries, these offer a near-complete absence of the hazards that make batteries the centre of attention in most risk assessments.

No overheating

With many other battery types, overheating is a serious concern because of thermal runaway. This is when an internal chemical problem occurs due to insufficiently cooling. That extra heat creates an exothermic reaction, making the battery start generating its own heat.

This creates a heat-based feedback loop. The overcooked battery makes itself hotter, which causes the heat-generating reaction to spread, making the battery even hotter, causing the reaction to intensify further, and so on.

Whatever the issue that causes this, whether it’s mechanical damage, a short circuit, or a cooling malfunction, the result is the same. Hazards range from simple casing damage to toxic fumes from melting plastics, to even potential fires if combustible materials are kept anywhere near the batteries.

LiFePO4 batteries avoid this problem with a combination of chemical stability and physical robustness. Because of the chemicals involved, and the solid state they all exist within, LiFePO4 batteries both stay stable at a much wider range of temperatures and heat up far slower when they do.

Other battery types, such as Lithium Cobalt Oxide and Lithium Nickel Cobalt Aluminium batteries heat up at rates of 470C per minute during thermal runaway. Lithium Nickel Manganese Cobalt is marginally better, heating up at 200C per minute. But LiFePO4 batteries are radically more stable, heating up at a rate of just 1.5C per minute. Also, thermal runaway only happens when LiFePO4 batteries reach temperatures approximating 200C, a fully 25% higher than other Lithium-based alternatives.

With such a slow thermal runaway rate, and a much higher threshold where such a problem would ever happen, overheating with LiFePO4 batteries becomes functionally impossible. This is why Wise Robotics and Hikrobot chose these batteries for our AMRs.

No combustion

Overheating near flammable items is not the only cause of battery fires. In many circumstances, such as too much charge, too little, or a charge that happens too fast, other types of lithium-ion batteries are vulnerable to catch fire spontaneously, or even potentially explode.

Unlike many other types of batteries, LiFePO4 batteries represent radically lower risk. They use a much more stable chemical composition and charging arrangement that makes them much safer in a far wider range of circumstances.

LiFePO4 batteries feature solid-state internal structure, as opposed to the liquid/semi fluidic states used by other batteries. This makes the kinds of chemical changes that lead to combustion much rarer. The battery as a whole is more stable and less vulnerable to external pressures that could lead to combustion.

LiFePO4 batteries also have a far stronger chemical composition when compared to other alternatives. The covalent bonds between Phosphorous and Oxygen in the PO4 section of LiFePO4 are extremely robust. Far more so than the bonds between Iron and Oxygen in the various other battery types that you might find in other types of robotics. With the Oxygen atoms more firmly contained, combustion becomes radically less likely. Even in the event of short-circuit, overheating, or physical puncture, LiFePO4 batteries mean your risk of fire is radically reduced.

No hazardous materials

Batteries may be safe and stable when the warehouse is functioning normally and everything is moving according to plan. But health and safety operations need to consider the edge case scenarios as well as the everyday periods of extended normalcy.

In the event of serious physical damage, many other types of batteries present a clear and present danger. Chemicals found in many other types of batteries like Nickel and Cobalt can be extremely hazardous when not properly contained, such as during a fire, or if a battery’s structural integrity has been compromised.

Contact with Nickel can cause cardiovascular and kidney disease, fibrosis of the lung, and various forms of cancer.

Exposure to Cobalt can cause severe abdominal pain, impact thyroid function, cause cancer, and can create potentially fatal cases of what’s called “hard metal disease”.

LiFePO4 batteries are a much safer alternative. Containing neither Nickel nor Cobalt, LiFePO4 batteries present far less danger should they become structurally compromised. LiFePO4 batteries are also completely solid, meaning that any structural compromise is far less likely to spread any of its contents in a way that could cause direct exposure to nearby staff.

Discover Wise Robotics safety systems

LiFePO4 batteries are a key component of Wise Robotics commitment to making the solutions we offer as safe as physically possible. Combined with the suite of sophisticated sensors that prevent collisions, and the emergency failsafe systems placed within easy reach, it’s easy to see why the systems associated with flexible robotics represent a radical change for warehouse automation.

If you’d like to learn more, come and see for yourself. Wise Robotics owns and operates Europe’s first flexible automation demonstration centre. You can watch what happens when industry 4.0 goes live, and discover why the robotics revolution isn’t coming. It’s already here.

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