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Product category: Electrical and Electronic Testing and PAT Equipment
News Release from: BTech Battery Validation Systems | Subject: Battery monitors
Edited by the Engineeringtalk Editorial Team on 28 November 2002

Battery monitors cut the odds of
unplanned outages

Modern battery monitors measure such parameters as voltage, current temperature and impedance and can also allow for variations in a battery's performance during its life.

The role of monitoring process and equipment has been going on since the industrial revolution In ever-increasing spirals of demand and sophistication, everything including stationary batteries is fair game for some form of monitoring

The most intelligent of these monitors is the educated human with sufficient relief for rest and nourishment.

Beyond that, forms of machinery and electronics, assisted by software intelligence, perform the majority of monitoring duties.

Today's competitive marketplace has placed demands on the human work force that require assistance from the hardware and software based alternative.

Stationary batteries, as the lifeline for UPS and quality power equipment, have landed in the middle of these monitoring scenarios.

If space weren't a problem, long proven vented cell designs would dominate in all applications.

In essence, maintenance is imperative for any battery - particularly VRLA cells, where there is no possibility of looking at electrolyte levels or indeed viewing the plates as may be done with the Rolls Royce of all batteries the plante cell.

On the other hand the cold fact is that to repeatedly monitor every individual cell is an onerous, time consuming and expensive alternative.

Thus one has to investigate the problem of finding an alternative and more economical solution to manual maintenance.

As far as the writer is concerned the answer from UPS manufacturers offers a simple form of maintenance in virtually every case.

This won't provide a first class detection of any faults; a sophisticated monitor is clearly the answer, irrespective of the high initial costs.

Such devices are available to measure such parameters as voltage, current temperature and impedance and indeed can also allow for variations in battery performance during its life.

The new approach has been not only to provide all this information but to reduce the mass of cabling between the individual cell and the monitor - by using a daisychain system.

This ensures that the cabling between the batteries and the monitor are simplified without compromising monitoring effectiveness.

The following case study illustrates the point.

A US west coast manufacturing company used the battery monitor to exact as much duty from the battery system protecting their process control as possible.

The company performs this knowing the risks involved but feels its knowledge of the VRLA battery type history and the reliability of the monitoring device allow them to reduce the odds of unplanned outages and exact financial gain from their capital investment.

The battery system consisted of five parallel strings, each containing 32 six-cell monoblocs.

All monoblocs were within manufacturers' float voltage limits with an average of 13.63V.

However, four units were exhibiting impedance values above maintenance limits set by the monitor manufacturer (10%).

Three, including unit 64 were above the critical limits selected (15%) at 30% or better.

This particular sic-cell monobloc battery (unit 64) has exhibited higher impedance than normal since the monitor was installed.

Unfortunately battery monitors seldom make a suspect cell any better.

They may point to environmental and conditioning factors but once a cell is in its downward spiral of life, there is only the reporting of degree.

The owners decided to use the slope level alarm as the suspect monobloc already passed through the critical transition alarm set for the battery string.

The unit consistently alarms as a slope value of 10mohm per week is exceeded and the value was 35% above its critical limit.

Interpreted, this means that it is 45% above the impedance for a new cell, 2.5mW.

As the battery manufacturer has graciously agreed to replace the defective unit at the 50% point, and the trend is safely linear, a new unit was ordered based on the information provided by the battery monitor.

Hundreds of monitor installations were reviewed for this article and it was clear that despite the engineering involved with the data measurement and collection, the dissemination of that information is key to the user.

There is a unique opportunity to provide guidance to the industry as a whole for battery monitoring solutions.

The IEEE has produced a document to be titled, "Guide for selection and use of battery monitoring equipment in stationary applications".

The IEC has issued a document entitled "Guide for the use of monitoring systems for lead-acid stationary batteries".

The author wishes to acknowledge Allan J Baum of BTech, along with Bart Cotton of Data Power, Sacramento, CA, whose participation and guidance contributed to the contents of this article.

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