Forklift truck (FLT) power options typically fall into three categories – diesel, gas (LPG), and electric. Internal combustion engine trucks are good for intensive work, as they are easy to refuel, but so too loud and limited to work outdoors. Gas-powered FLTs, meanwhile, typically have a low purchasing cost and can be used both indoors and outdoors, but refuelling requires more effort and experience.
The electric truck, on the other hand, can also work indoors and outdoors, whilst producing zero emissions and being easier to handle. A downside to electric, perhaps, is that batteries deplete and need charging up, among other maintenance needs. Therefore, if you’re an operator in charge of an electric truck, knowing different battery management techniques to get the most out of the ‘workhorse’ could mean the difference between job well done and job incomplete.
Luckily, FLT trade associations and manufacturers have a range of tips and advice when it comes to battery management, while different products have been placed on the market to give operators a helping hand.
TRADE ASSOCIATION ADVICE
The British Industrial Truck Association (BITA) is a UK trade association for FLT manufacturers and suppliers, and suppliers of associated components and services. Technical manager David Goss says that, first of all, it is important to recognise that there are two distinct battery technologies for materials handling equipment – lithium-ion (Li-ion) and lead-acid (PbA) – and their management requirements are different.
Lithium-ion batteries are virtually maintenance free, thanks partly to a sophisticated battery management system (BMS) that monitors and optimises battery condition, he explains. Although the capital cost of Li-ion is comparatively high, this should be considered against the substantial benefits available:
● Energy efficiency is high during charging, discharging and when recovering energy, such as when the truck is braking;
● Where two-or three-shift usage is envisaged, very rapid opportunity charging, taking place during short periods such as operator breaks, removes the necessity for battery change-out between on-truck use and a charging station.
“Be aware, however, that the power supply requirement for fast charge is higher, in direct proportion to the time saved,” says Goss. “The lithium-ion chemistry used on materials handling equipment is different from that used in the automotive industry. This means that the batteries are much more stable. However, irreversible damage can occur to the cells if the charge is permitted to fall below the critical undervoltage limit.
“All batteries suffer at temperature extremes, and Li-ion batteries intended for cold applications will require heaters and cooling fans, but these draw power even when the equipment is idle, and it is vital to maintain sufficient power to the BMS in order to protect the battery. If this is not done, the battery could enter a shutdown state that may not be recoverable, and eventually the battery may become unstable.”
Goss says that regular visual inspection, and an annual test by a specialist technician, should be the only maintenance required for Li-ion. In fact, repairs should only be attempted by a specialist.
THE ACID TEST
With all the interest surrounding lithium-ion, it “would be wrong” to think that lead-acid battery development has stagnated because “considerable advances in lead-acid battery technology have also occurred”, including reducing maintenance, increasing charge rate and capacity, and permitting opportunity charging.
Goss reports: “With lithium-ion batteries there is likely to be little loss of truck performance as the state of charge declines. Historically, some trucks with lead-acid batteries exhibited a loss of performance roughly proportional to the state of charge. This was bad for productivity, but provided warning to the operator that it was time to head for the charging station. Modern trucks, especially those with AC drives, are much less prone to this.
“Charging of PbA should be carried out in a dedicated and well-ventilated area, as detailed in BS EN 62485-3:2014. This is because hydrogen gas will be emitted during charging, and this represents an explosion hazard. One of the benefits of Li-ion is that no gas is emitted during charging. Also, unlike Li-ion, PbA batteries can be sensitive to the rate and duration of charge, and also to the level of charge present when charging commences. Unless the battery and charger manufacturer have specifically stated otherwise, it is prudent to commence charging when the state of charge is approaching 20%, and to continue charging until full.
“Cell balancing, or equalisation, is required when different cells develop slightly different power characteristics. On Li-ion, the BMS does this automatically. With lead-acid batteries, sulphate deposits on the plates may cause some of the cells to hold only a partial charge when others are fully charged. Typically, equalisation charging is a longer process than an ordinary charge, but the requirements vary according to equipment type and application. The expertise of your battery supplier is an invaluable resource.”
Goss adds that the battery is an expensive item to replace, so investment in best practice is well repaid. Correct PPE is also essential, due to the risk of electric shock and potential contact with acid and gases.
“Topping up, also known as watering, must only be done with clean distilled water, as any impurities will rapidly degrade the battery. Watering can be carried out manually to each cell, with a low-pressure float in each cell and single connection point or, most rapidly, with a high-pressure system which automatically cuts off when the correct level is reached in each cell. Typically, this is a weekly requirement; however, low water consumption designs are available which can extend this to several months. It is important that the electrolyte is only topped up to full when the battery is fully charged, otherwise the battery acid will overflow. This is because the electrolyte level rises and falls according to the state of charge. However, all the plates should be submerged before commencing charging in order to prevent overheating,” he adds.
“Recording and monitoring specific gravities and cell voltages when fully charged (after termination of charge, and when voltage stability has been obtained), provides a good indication of battery health. Cleaning is [also] an important maintenance activity for lead acid batteries. Residue on and around the battery will be highly corrosive and must be removed appropriately and without contaminating the cells.”
BITA guidance note GN69, Lithium-ion Traction Battery Applications, and guidance note GN68, Lead Acid Traction Battery Applications, can be purchased online (www.is.gd/dotuju).
Forklift manufacturer Toyota Material Handling has its website updated regularly with company news, case studies, advice, blog posts and product news. It too provides tips for effective battery care, based on advice from its technical team and product managers (www.is.gd/irahok).
It explains that it is important to stick to the manufacturer’s guidelines, especially when a battery is new, because a new battery must be used and re-charged a certain number of times before being topped up. “This differs with batteries from different suppliers, so make sure you read the information that comes with your shiny new battery very carefully,” it explains.
To get the most effective performance out of a battery, operators should also ensure that they use most of its power before recharging. Like Goss, the company says that a generic rule of thumb is that the battery should be at 20% or less charge to avoid damage.
And, when it comes to recharging, operators should allow enough time for the battery to charge fully, and shouldn’t use the truck until it has finished. “Once your battery is fully charged, you should allow it to finish gassing and fully cool down before using it again,” Toyota Material Handling says.
There are many products available for FLTs to help operators get the most out of their batteries. Toyota Material Handling, for example, offers ‘I_Site’, a truck management system that connects to fleets, collects data and gives an overview of what’s happening, as well as what can be done to optimise operations (www.is.gd/wagowe). Features include battery monitoring; truck/driver utilisation; a web portal/mobile app; remote driver access, driver admin and licences control; and smart access (card or fob).
Stored energy solutions provider EnerSys, meanwhile, has introduced the Truck iQ smart battery dashboard, which aims to give real-time visibility of a truck’s battery status, enabling drivers to optimise their battery’s utilisation and power management, while avoiding the risk of damage or productivity loss due to incorrect usage.
Drivers can easily see and understand their battery’s condition and associated parameters from their seat, in real time. Battery data is measured by wireless sensors located on the truck battery, and collected by a compact, harness-mounted Wi-iQ3 battery monitoring device. The battery monitoring device relays this information to the Truck iQ smart battery dashboard via Bluetooth. This communication channel is established quickly and automatically on power-up, without need for driver intervention. Information delivered includes real-time state of charge, and alarms and alerts for the following battery parameters: temperature, electrolyte level, low state of charge and cell unbalance.
The dashboard’s primary screen features a prominent graph showing state of charge, remaining work time and battery temperature. Battery warnings relating to ‘go-to-charge’ – accompanied by a buzzer – and high battery temperature, electrolyte level or unbalance are also visible. Also displayed are the user ID, worked time, and the number of Ah that have been re-injected into the battery by vehicle braking.
“The Truck iQ smart battery dashboard is different, because it presents truck and battery information in real time to the driver on the job, in an easily understood format. This helps to prevent truck misuse, while improving battery utilisation and service life. It also boosts efficiency and energy management,” comments Orjan Eriksson, commercial application manager for monitoring and solutions at EnerSys EMEA. “In summary, the Truck iQ smart battery dashboard allows each vehicle driver to make his own contribution to the power efficiency and operational productivity improvements.”
Independent battery sales and service supplier Ecobat Battery Technologies (Ecobat Industrial) also offers what it says is effective and efficient solutions that provide the answers required by customers. One example is its FULLlife battery and charger care packages.
FULLlife is said to provide customers with real-world benefits that enable them to forecast monthly expenditure and implement productive solution.
Just as they are able to rent a forklift, they can also rent their battery/charger combination, complete with a service package that covers day-to-day use and maintenance.
FULLlife packages are tailored to suit individual company requirements, but can include battery/charger combinations as required by specific application, fleet monitoring systems, battery watering (including the water), agreed reports on battery/charger fleet condition, cover for any size of fleet, fixed weekly/monthly fees and priority service call out.