Workplace injuries are all too common in warehouses, and battery maintenance for material handling equipment is a typical culprit. The ongoing maintenance required to keep flooded lead-acid batteries running presents a danger to the workers tasked with charging, watering and changing batteries.
Batteries come in power equipment on construction sites, in tractors, trucks and automobiles, and most of them contain hazardous substances like lead and sulfuric acid. Unless workers who maintain, recharge and operate batteries know the risks and how to mitigate them, they can suffer severe workplace injuries. Repetitive use injuries, such as sprains and strains are common, but unfortunately the highly corrosive electrolytes in batteries can cause respiratory irritation, eye damage, skin irritation and it can even erode tooth enamel. The sheer size of material handling batteries means that crush injuries also occur during battery changes. New Li-ion batteries eliminate most of these issues because they are self-contained and maintenance free. Iron phosphate, a subset of Li-ion is the safest chemistry available, and its long cycle life means that it will last the lifetime of the truck.
The Risks of Lead-Acid Batteries
The charging of lead-acid batteries is hazardous, but many workers may not remember this as the activity is so routine. The three most common risks are from hydrogen gas formed when the battery is being charged, the sulfuric acid in the battery fluid- with exposure from spills and leaks, and physical injuries from the batteries’ weight. The corrosive electrolyte material is shown in this first image of a damaged lead-acid battery. This is an overview of the risky maintenance for lead-acid batteries:
- The fluid level is extremely important and a safe level requires regular watering. Overwatering and underwatering can both damage the battery. If too much water was added before charging, the electrolyte levels will expand and cause the battery to overflow and damage the battery.
- Conventional batteries contain a liquid “electrolyte” which is a mixture of sulfuric acid and water. The plates in a lead battery contain an active material that should be continuously bathed in electrolytes while oxygen and hydrogen gas are released during charging.
- When batteries are being recharged, they generate hydrogen gas that is explosive in certain concentrations in air, so the ventilation system must provide enough fresh air to prevent an explosion.
- The electrical voltage created by batteries can ignite flammable materials and cause severe burns. Workers have been injured and killed when loose or sparking battery connections ignited gasoline and solvent fumes during vehicle maintenance.
- Wear personal protection equipment such as protective eyewear and gloves when working on batteries. To avoid splashing acid, personal protective equipment such as chemical splash goggles and a face shield must be worn.
- First aid facilities, eye wash stations and emergency showers are necessary to reduce the severity of accidental contacts.
Li-ion Batteries Growing More Common
Li-ion batteries are becoming more and more common because of their long cycle life and short charge times, but they also greatly reduce the risk to the workforce when they are implemented in a warehouse environment. Li-ion batteries are made up of cells, just like lead-acid batteries. The cells have an anode and a cathode with a separator and electrolyte in between. Unlike flooded lead-acid cells, the li-ion cells are sealed and have many safety factors designed in them. The cathode material is the main determining factor in the cell’s performance. In the battery power market today, there is a myriad of available battery cathode chemistries to choose from. It is a critical decision which not only impacts how well the product will operate but also how safely it can operate. Factors such as how much power is required, the time required to charge, operating temperatures, operating environment, packaging dimensions and weight are all examples of key parameters that must be considered.
While higher energy li-ion chemistries are available, Lithium iron phosphate (LFP) is safest with the longest cycle life due to its stable chemical make-up. A demonstration of how much more stable the LFP chemistry is compared to the high energy Lithium Cobalt Oxide (LCO), used in consumer electronics, is to compare the thermal runaway temperatures- the high temperatures at which the chemistries begin to become unstable and volatile. LCO has a much lower thermal runaway temperature of 150°C (302°F) compared to LFP’s thermal runaway temperature of 270°C (518°F). This large difference shows LFP to be the much safer of the two lithium chemistries.
The physical construction of the cell also affects its safety. All lithium batteries contain a critical component called the separator, which is placed in between the anode and cathode layers in the electrode. The separator limits the chemical reaction of the electrode and helps to prevent thermal runaways by closing its porous structure at high temperatures. The safest Li-ion cells incorporate ceramic separators. The ceramic material is resilient at high temperatures and helps prevent the breakdown of the separator that occurs during a thermal runaway event.
The electronics of the Li-ion battery also provide protection against safety events, with incorporated fuses and protection against over-charge, over-discharge and high and low temperature charging. These battery “smarts,” combined with the long cycle life and short charge time seamlessly integrate with the material handling equipment. The fact that the battery is virtually maintenance free over the lifetime of the truck, eliminates the possibility for user error and greatly reduces the risks in the workplace. WMHS
Robin Schneider, PhD, is Director of Marketing at Green Cubes Technology Corporation, a leader in the development and manufacturing of reliable lithium power systems that enable OEM and enterprise customers to transition from lead acid and internal combustion engine (ICE) power to Lithium-ion battery power (www.GreenCubesTech.com).