Capacity matters

02 April 2008

Working at height inside, in poorly ventilated areas and on sites where combustion engines might cause unacceptable hazards, is where battery powered access equipment comes into its own. As aerials are increasingly adopted in these environments, how can users and rental companies ensure that the condition of their batteries does not compromise the performance of their machines?

We are all familiar with the process of charging a battery, but how can you easily establish the capacity and SoC (state of charge) of your batteries and whether they are mismatched? Knowing the true condition of your batteries can reduce unexpected downtime, improve the reliability of rental equipment and reduce false warranty returns.

Cold cranking amp

One method of measuring battery condition, AC conductance, was introduced in 1992. It measures the conductance from which the battery's CCA (cold cranking amp) is estimated. It is quick and non invasive but AC conductance can't read capacity, so has limited use for the deep cycle batteries that are commonly used on electric scissors and other battery powered platforms.

Battery capacity is commonly measured by applying a full discharge. This is an accurate but cumbersome method and wears down the battery unnecessarily. However, in the last 15 years several rapid test methods have emerged which, according to Isidor Buchmann, founder and CEO of battery testing company Cadex Electronics, have eliminated the need to use the full discharge method.

Rapid measurement

In the last five years progress has been made towards making capacity estimations using a technology called EIS (electro impedance spectroscopy). EIS is not new; equipment using this technology been available for decades, but required dedicated instruments and a computer to analyse the data. The set up was expensive, the machinery was large and had to be moved about on wheels, and trained staff were required to carry out the time-consuming analysis.

Now, however, Mr Buchmann's company has produced a handheld unit that uses EIS to test for capacity, conductance and state of charge. He tells AI that the new Cadex Spectro CA-12 been designed to solve the problems of traditional EIS by using powerful signal processors and more particularly a patented algorithm. The device can measure capacity conductance and state of charge in 15 seconds.

Mr Buchmann says he is sure that, in time, measuring battery performance through non invasive means such as this will become the acceptable standard, making discharge methods redundant.

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