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Executive Report: The debate heats up Following recent concerns about Lithium-Ion batteries in laptops, EHN power tools specialist Phil Mist asks whether cordless equipment in hire fleets could be affected. The recent major recall of Lithium-Ion batteries by Sony and Dell sent shivers down the spines of many in the power tool world. The reason for the drastic action is that certain batteries have overheated and caught fire when fitted to laptop computers. Power tool manufacturers claim their Lithium-Ion batteries are quite different. Put simply, a laptop computer battery is charged and discharged relatively slowly and at a low amperage, whereas a power tool’s charging cycle is much more aggressive, with lots of power being packed into the battery in the shortest possible time. However, power tools are often abused, resulting in a heavy discharge cycle that can cause a rapid rise in the core temperature. In the last few years, laptops and cordless tools used the same type of battery. NiCads (nickel-cadmium) were the only choice available initially, and all were recharged using a twelve, three or a one-hour charger (the so-called fast charger). Regardless of the total charging time, all of them worked by switching off when the battery reached a particular core temperature, usually around 40°C. Serious consequences Since heat build-up is damaging to any battery, and with heat being generated during not only the charging cycle but also the discharge cycle, it can have serious consequences. In the case of a power tool being abused, the battery is expected to operate at, or even above its rated capacity. Not surprisingly, many have failed. Batteries attached to laptops, on the other hand, were not as prone to succumb because of the less demanding situations in which they operated. With the advent of electronic battery chargers, and other more carefully controlled charging systems, many of the overheating problems experienced with power tool batteries have been more or less resolved. However, in the last few years, power tool companies have attempted to replace environmentally harmful Ni-Cad batteries with ‘greener’ NiMH (nickel metal hydride) batteries. At the time of their launch, they were said to offer more power, less build-up of heat, and little or no so-called memory effect, but with hindsight they were overrated. Five years on, we now have Lithium-Ion. Their features are tempting, including more power, less weight and a smaller size, leading in turn to more compact power tools. But because of the problems now being experienced in the computer industry, I attempted to obtain answers about the reliability of the new batteries in power tools. Unfortunately, I met with a series of standard replies that were somewhat disappointing. According to scientists I have spoken to, lithium is more sensitive to heat than any other material ever used in battery construction. It has a melting point half that of nickel or cadmium and, whilst being much more environmentally friendly, it would seem to be critical that Lithium-Ion batteries are cooled during charging or discharging. If lithium is so sensitive, and the laptop problems would seem to confirm this, what could happen to power tool batteries? The attitude from most power tool manufacturers has been, ‘Problem? What problem?’, yet there are rumours of at least one company having already experienced overheating problems with a new Lithium-Ion cordless tool range. Most of the manufacturers promised me a statement, but at the time of writing none has been received. And two companies claim their batteries are so different from the others that they have no problems. If – and it is a big if - there is actually a problem with Lithium-Ion batteries, any tools used in the hire industry would expose it quickly. Its customers are more demanding than any others. In addition, hire companies’ requests over the years have led to power tools and other equipment being more robust, better designed and more user friendly. So, even though there may be no ‘problem’, to quote the manufacturers, they should give us the facts quickly. • Executive Hire News › Archives › October 2006 › Executive Report › The debate heats up
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