opinion AMHSA l Li-ion: a power of good
In this month’s article in the series from members of the Automated Material Handling Systems Association (AMHSA), Kenny Watson, European business development manager for JBT Corporation, explains how lithium ion batteries are set to revolutionise automated guided vehicles.
L
ithium ion batteries (also known as Li-ion or LIB) are a family of rechargeable battery types that are brand-new to providing traction power for free-roaming materials handling vehicles. Of course, they have for a few years been common in consumer electronics, powering items such as mobile telephones and cameras. Beyond this market, lithium ion batteries are growing in popularity for military and electric vehicles and aerospace applications.
At the recent CEMAT exhibition in Hanover, we saw the first ever lithium- ion-battery-powered pallet truck. In addition, a major lift truck concern has entered an agreement to trial lithium ion batteries at the distribution centre of a major supermarket.
If there is an ideal materials handling application for Li-ion, it must be automated guided vehicles (AGVs), as
If there is an ideal materials handling application for Li-ion, it must be AGVs, as here we could really reap the benefits of this new battery technology.
here we could really reap the benefits of this new battery technology.
Smaller and lighter
So what are the benefits? Li-ion batteries have one of the best energy densities in the battery business. This gives them a superior weight to power ratio. In comparison to the very heavy lead acid batteries that are now the typical power source for forklifts and AGVs, a lithium ion battery that could perform the same work shift would only weigh in at some 12 to 18kg. This equivalent- capacity lithium ion battery would only
52 ShD October 2011
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be about the size of a briefcase and could easily be carried by one person to a local charging point, with the battery case incorporating a carrying handle for this purpose.
This avoids the need for heavy lifting equipment if battery changing for multi-shift working is required. With Li- ion batteries, the AGV of the future will be smaller and neater, whilst its overall weight will be significantly lower.
No memory effect
Lithium ion batteries have no memory effect, a factor that can swiftly deteriorate other types of traction battery when they are not given deep charge/discharge cycles. For example, the typical capacity reduction on a lead acid battery is just over 30%. Li-ion batteries also offer slow loss of charge when not in use – a useful advantage in a seasonal industry.
In addition, they can work at very low temperatures without problems, making them ideal for cold stores – which, given the harsh conditions, could be seen as growth area for AGVs.
Faster, simpler charging Many of the advantages of Li-ion batteries over lead acid ones relate to charging issues. Charging a Li-ion battery is fast compared to lead acid, taking about a hour and a half to give a full recharge of a battery suitable for an AGV, compared to at least six hours for a lead acid battery. Lithium ion batteries are also very suitable for spasmodic opportunity charging, which is a very common occurrence in AGV-based handling systems.
In addition, there is no need for a dedicated, ventilated charging bay as, unlike lead acid batteries, no fumes are
emitted during the charging process. The Li-ion battery connects with the vehicle like a plug-in cassette, with no need to make a series of connections as with lead acid batteries. In fact, there is no need to have specialised technicians to change and charge batteries. Whereas the deionised water in lead acid batteries needs to be topped up once a week or so, there is no need to top up a Li-ion as there is no fluid in the system. As well as having no water, there is no acid, which eliminates the possibility for acid spillage.
Cost comparison
So why have Li-ion batteries not swept their lead acid rivals out of the traction battery market before now? It’s a matter of cost. Lithium ion batteries are some nine times more expensive than lead acid ones.
But we need to look further than these figures to get the true picture. Discharging a lead acid battery to 50% and recharging would result in a life of around 1500 cycles, whereas the same for a Li-ion could give up to 10,000 cycles. Now add into the equation the fact that their suitability for opportunity charging means that Li-ion batteries eliminate the need for customers to invest in two batteries per shift, as they usually do for lead acid batteries. Don’t forget that there may also be labour savings due to the maintenance- free operation of Li-ion batteries. Finally, work out the savings that opportunity charging and shorter charging times secure in terms of reduced downtime. Using these more comprehensive calculations, the future for lithium ion batteries in AGVs looks very bright. ●
www.amhsa.co.uk
opinion
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