You have to accumulate to accelerate – the right choice of battery plays a critical role in the efficiency of the electric truck fleet. Lucy Tesseras investigates.
When scouting out a new electric forklift it may be the load capacity, lift height, speed and size that initially grabs an operator’s attention, but all those things become fairly redundant if the right type of battery isn’t chosen to power the machine.
Unlike a toy car, it’s not a case of popping in a couple of double As, turning it on and watching it go. There is a myriad of options, from standard lead-acid batteries to lithium-ion models and maintenance- free types, all of which come in a number of sizes and with a plethora of charging options.
Add to that the cost, safety concerns, the environmental aspect and maintenance and it becomes a more complicated matter.
Craig Johnson, Jungheinrich UK’s marketing manager, says choosing the right type of battery for the right application is critical, and a number of factors should be considered, not least the question of whether the truck is expected to operate single or multi shifts.
However, there is a trend towards low maintenance batteries which require longer intervals between services. He says: “Jungheinrich’s low-maintenance batteries used in conjunction with our special charging technology and electrolyte circulation system, which enables air to be pumped into the battery to thoroughly mix the battery acid, results in faster charging and less servicing work because water consumption is lowered. And that means less truck downtime and even more impressive production efficiency.”
Jungheinrich provides its own range of batteries and chargers for its electric trucks, which it says enables it to simplify truck maintenance procedures.
“It is not uncommon in the event of an electric-powered truck breaking down for the truck supplier to blame battery malfunction for the problem and the battery supplier to argue that the cause of the malfunction lies with the mechanics of the machine itself.
“Because Jungheinrich is a one-stop shop capable of offering truck, battery and charger, our clients never face such potentially awkward ‘blame game’ problems,” adds Johnson.
The company recently launched JiBOS, the Jungheinrich Intelligent Battery Organisation System, which is designed to enhance efficiency of the battery pool, by allowing a forklift truck fleet’s battery usage to be monitored and controlled.
When it comes to swapping batteries, the system highlights the most appropriate battery to take in the charging area via an LED display.
Jungheinrich’s sales director Bill Goodwin reckons that “operators naturally select the most conveniently-located battery when it comes to changeover time” which often means batteries placed nearest the entrance to the charging bay are most frequently picked.
“Overused and insufficiently cooled batteries have a dramatically reduced capacity and life. JiBOS promotes longer battery life through uniform usage and optimises maximum available battery cooling time. As a result, both battery and charger fleets age at the same rate, which means reduced maintenance and operating costs for the user.”
JiBOS is already in operation at a number of retailers’ warehouse facilities and in all cases on-site battery charging costs are reportedly down. “Furthermore,” says Goodwin, “at one user site, four year old batteries that would normally be expected to be holding a lower charge are actually holding a charge for longer, which means they need less frequent changing.”
And at another user’s facility, the system has enabled the company to reduce its battery pool so significantly that floor space once dedicated to battery charging has been converted into an additional storage area.
Similarly, battery manufacturer Hoppecke helped French hypermarket chain Géant create a floor space saving of 70 per cent by installing a fully automatic powered two level battery changing system for the company in Poland.
The system accommodates batteries and chargers for 30 power pallet trucks, 44 low level order pickers and ten reach trucks. Drivers can now change batteries in three minutes with no physical effort and it has enabled Géant to move to a two shift operation.
All batteries and chargers supplied use Hoppecke’s trak air system, which comprises a traction battery with electrolyte circulation and a microprocessor-regulated charger to create rapid and gentle charging of the battery.
“By constantly pumping air and circulating acid the life of the battery can be extended as charging the battery is that much faster,” says Bernard Molloy, managing director of Hoppecke.
Charging times can be cut by around two and a half hours, which also helps to minimise operating costs by reducing energy consumption by up to 35 per cent. In addition, battery availability is increased and as its temperature is kept down the life of the battery is prolonged.
“Batteries normally last for around 15,000 cycles, but this can be boosted to 18,000 cycles with a good high frequency charger,” adds Molloy, meaning it will last seven to eight years, rather than the usual five.
A battery normally equates to 20 to 30 per cent of the capital cost when buying a forklift, “but in a way that becomes irrelevant because the money spent charging equipment over its lifetime is variable,” says Molloy.
As big a concern as cost is in the current climate, it is important operators don’t get seduced by the price of smaller batteries. “It might look cheap on paper,” he warns, “but as batteries need to be charged more often customers could end up getting stung by higher electricity costs and it could easily end up being more expensive in the long-run.”
Hoppecke is the preferred battery dealer for forklift trucks supplied by Barloworld Handling. It uses the company’s high frequency chargers and low maintenance batteries as part of its battery management service.
Barloworld’s Roger Massey explains: “The advanced batteries feature a unique air circulation system which means they can be fully charged quicker with up to 75 per cent reduction in the emissions produced by charging… even opportunity charging is possible without damaging the battery.”
To ensure full battery capacity over the life of a contract, Barloworld uses a battery regeneration system called MACBAT, which optimises battery performance and removes the sulphation on battery plates, helping capacity and shift life to be maximised.
“The system will also regenerate sulphated batteries, helping to minimise battery replacement costs,” adds Massey.
According to Stanley Handling, gel batteries, and increasingly absorbed glass mat (AGM) cells, offer a safer alternative to lead-acid batteries, particularly in deep cycle applications, as the sealed nature of the cells minimises the chance of gas escape, leakage or corrosion, as does the use of gels or absorbent sheets rather than a liquid electrolyte. They are particularly good for applications where there is a fire or explosion risk or in food and other “clean” environments.
In storage, gel and AGM batteries will last between six and 12 months between recharges, compared to about three months for conventional batteries. Degradation rates are also lower and as sealed units they require no topping up.
Stanley Handling uses this type of cell in its specialised pallet trucks and stackers.
It recently supplied missile manufacturer MBDA with stacker-based missile rotation units and similar units to be carried on board the aircraft. The company also uses them in all its PowerMate stair climbers as they can be used at varying angles with no danger of spillage.
Gel and AGM batteries do demand a premium price though. Monobloc 6v/12v batteries tend to be about 35 per cent more, while 2v cells, which are linked together in a series to give the required voltage, are up to 50 per cent more expensive.
Another alternative to traditional batteries is hydrogen fuel cells, but Bill Goodwin, Jungheinrich’s sales director warns operators not to believe the hype.
Hydrogen fuel cells have been billed as a sustainable alternative to more conventional batteries as hydrogen is one of the most abundant fuels on the planet, but as they have to be produced as a compressed gas or cooled to a liquid form before being used that’s not necessarily the case.
Both processes involve the use of other energy sources, such as traditional fossil fuels which Goodwin says is “counterproductive”, or renewable sources like wind, solar and tidal-based schemes, but he doesn’t believe these have the ability to provide anywhere near the kind of energy levels needed for mass production.
Furthermore, he says the growing of crops to provide bio-fuels instead of foodstuffs is “ethically questionable” and the use of nuclear fuels, while arguably more attractive, is going to be less suitable for British users “given the UK government’s reluctance to embrace the nuclear option”.
Additionally, he says comprehensive and reliable evaluations of the benefits of hydrogen as a fuel source for materials handling equipment have yet to be undertaken and as such, believes “the lead-acid battery currently remains the industry standard forklift power source”.
Going forward, he suggests in the short-term lithium-ion batteries will be able to offer rapid charging, long running times and compact dimensions, and over the next two to three years, methanol fuel cells will be widely available.
“Hydrogen could well prove viable as a forklift power source, but because of the issues that still surround it, hydrogen-powered forklifts will not be seen in any significant numbers in Europe for many years.”
Safety: Acid test of safe operation
The British Industrial Truck Association has outlined a number of pointers for the safe handling of forklift truck batteries.
1. Create a safe working space
A safe working environment must be created. Bob Hine, BITA’s technical consultant, says: “Assign a restricted area for the sole purpose of battery charging and provide a warning sign in accordance with ISO 6405, denoting an electrical hazard.”
It is also vital to ensure that smoking, use of naked flames, or welding operations are prohibited in the vicinity, and the space is kept dry, clean and clear of spillages.
The battery charger must be positioned away from moving trucks and an adequate mains electrical supply needs to be provided for each charger, together with fuse or circuit breaker protection and an isolator that the operator can easily reach.
2. Wear appropriate clothing
Operators should always wear protective clothing, including acid-resistant gloves, goggles and rubber footwear. Synthetic fibres, jewellery and metallic watches should not be worn and operators should always use tools with insulated handles.
3. Be prepared for accidents
A powder fire extinguisher, water supply, eye bath and eye medication should be kept in the battery changing area, along with some form of neutralising alkali such as soda ash, sodium carbonate or sodium bicarbonate.
If a spillage of acid does occur the affected floor area should be neutralised as quickly as possible using an alkali. If skin comes into contact with acid it should be washed off with clean water, and if it gets into the eyes they should be immediately flooded with copious amounts of water before seeking medical advice.
4. Encourage safer working practices
Batteries should always be disconnected when carrying out maintenance or repair work on electric trucks. The battery top should be kept clean and dry, while terminals should be clean and kept free from corrosion with petroleum jelly.
After charging, the earthed terminal should be disconnected first and reconnected last, and batteries should always be kept upright when lifting.
5. Train operators adequately
Operators must be properly trained in safety procedures and best practice. BITA provides a number of booklets on the subject to encourage better working conditions.
EnerSys has introduced the Hawker XFC FLEX battery range, which thanks to advanced thin-plate pure-lead technology can be “opportunity” charged, used while partially charged or rapidly re-charged.
As such, the company claims the range offers up to 30 per cent more power density than similar batteries and needs little maintenance as no water topping-up is necessary.
Fast charging and deep discharge is made possible due to the alloy thin grid plates, which allow for the electrolyte to be absorbed in a microporous separator.
Whereas conventional lead-acid batteries should usually be discharged for up to eight hours then recharged for eight to 12 hours, the operating instructions for the XFC FLEX state: “use the truck and when not in use recharge the battery”. The battery can also be fully fast charged from 60 per cent depth of discharge in three and a half hours, helping to reduce downtime and increase productivity.
In addition, the range has minimum gassing and energy consumption can be reduced when used in conjunction with EnerSys’ high frequency chargers.Hydrogen-powered forklifts will not be seen in any significant numbers in Europe for many years.