Stretch Battery Life with Proper Monitoring and Maintenance
By Arun Patel, CEO, Access Control Group
Battery is the life line of electric equipment used in distribution centers, manufacturing plants, airports and many other facilities. Due to increasing air quality concerns and higher operating costs, more companies are moving towards battery operated equipment.
Best practices for proper charging, discharging and maintenance are crucial to maximize throughput and quicker ROI. These practices can be effectively implemented by electronically monitoring battery performance and make proactive decisions based on collected data.
Battery Basics:
There are several factors which affect the operation of the battery and its ability to deliver expected throughput. Many chemical reactions are affected by temperature. The chemical reaction of a lead-acid battery slows down by lowering temperature which results in a loss of capacity. A battery will deliver 100% of capacity at 77ºF; at 20°F the battery only can deliver 74% capacity.
Excessive heat will contribute greatly to reducing battery life by corroding the positive grids and by excessive gassing which loosens active material pasted onto the positive grid. Overcharging is the most common contribution to excessive temperatures and gassing in a battery.
Consistent undercharging of a battery will gradually run down the cells and result in one or more cells becoming completely discharged before the others, and may become reversed. Capacity and life expectancy are greatly reduced by undercharging. Periodic equalizing charges that return the cells to a normal condition are part of good battery maintenance. Over discharging will also cause permanent damage to the battery. Recharging is more difficult and more time consuming. Often complete recharge is not attained and the undercharged battery is still providing power for your system. Consequently, it is over discharged even further, resulting in loss of capacity and pre-mature battery failure. Optimum battery life can be aided by limiting the Depth of Discharge (DOD) to 80%.
Material handling equipment fleet is vital to a company’s ability to move its products to market and represents a large capital investment. Scheduled maintenance programs are usually designed to keep the vehicle in good operating condition but the industrial battery is often overlooked and poorly maintained. By the time a battery technician is called in, damage has been done and may require expensive repairs or even premature replacement of the battery.
Charging Methods and Associated Issues:
A typical lead acid battery has a life expectancy of approximately 1500 charge/discharge cycles. Charged once per day, this equates to an approximate 5 year battery life. A battery that has been used for 6 or more hours and reduced to 80% discharge must be recharged for approximately the same amount of time. Once fully charged, the battery must have a minimum 6 hour cool-down period.
For a light-duty, one shift operation, that simply means placing the battery on charge after the shift. At the beginning of the next days shift the battery has been recharged , cooled and ready for the next shift. For a 2 shift operation, a second battery would be required and a 3 shift operation would require 3 batteries per vehicle to maintain the operating cycle.
Industrial batteries are expensive and if properly maintained, will give the full 5 year work cycle. To assure proper care and maintenance the owner needs to be able to monitor the use and recharging periodically to assure maximum return on their investment.
Fast and Opportunity Charging in Airport and Material Handling Applications:
Many charger manufacturers are selling fast or opportunity chargers with much higher than normal amperage input during the charging cycle. Their theory is that by recharging at opportunities during the daily work cycle, the need for changing batteries is eliminated, thereby reducing the capital investment in extra batteries. Fast or rapid opportunity charging places increased demands on the battery and makes proper care and maintenance even more important. If not properly monitored, the life expectancy of a fast-charge battery may be reduced from 5 years to 3 years or less due to the frequent charging and constant discharging. It becomes imperative that battery usage and maintenance be monitored frequently to assure full life expectancy. All batteries need to have weekly equalizing charges over a 6 to 8 hour period at slower rates to bring them back to a maximum charge level. Failure to do so will greatly shorten the life of the battery.
Fast Charging and Opportunity Charging of industrial batteries can be a great asset to fleet equipment managers charged with optimizing the productivity of their operations while reducing capital expenditures. Eliminating the process of rotating batteries between the charger, cool-down, and vehicle can save many thousands of dollars in batteries and personnel to do the changes as well as the space required for charging stations – if they monitor battery fleet for optimum charging, discharging and equalizing.
False Battery State-of-Charge (SoC) Reading in Fast/Opportunity Charging:
In fast and opportunity charging environment most end users face the issue of false reading on equipment’s BDI (Battery Discharge Indicator). Most if not all, BDIs supplied on forklifts, GSE and other equipment display battery SoC based on surface voltage. Since the battery is being charged multiple times in each shift, BDI is “confused” and often displays full battery and operators do not charge the batteries as a result. In some cases battery SoC falls below 20% but the lift cutout does not work because BDI “thinks” the battery is full. Drive components such as traction and lift motors can burn out or cause damage to other control components. Another hidden cost is lost productivity. Equipment manufacturers can rectify this issue by using BDI which operates based on current, not just voltage.
Recognizing this need, Access Control Group developed the CellVue a real-time battery state-of-charge gauge which works with CellTrac. CellVue mounts in view of the operator and displays Amp Hours, temperature, low electrolyte level, hour meter, service alert and lift-lockout.
Hot Cable Situations:
Poor crimping, wear and tear and stress on battery connector can cause poor connection which can result in excessive temperature at battery connector during charging. In extreme conditions, the connector can melt and in some cases it can catch fire. Monitoring cable temperature can help prevent serious damage to the charger, battery and/or facility.
Dual Cable Setup:
In a high current, fast charge environment, two cables are used to distribute current. Theoretically, current in both cables should be equal. But due to cable resistance and contact quality current can be different in each cable. If actual current is not measured through both cables, Amp Hours supplied to the battery can be wrong and hence battery throughput calculation can be wrong. CellTrac can measure current in both cables for accurate throughput calculation.
Tools to Monitor Batteries:
Battery cost has risen due to higher costs of lead. In addition poor battery management has direct impact on battery life and productivity of the operation. End users cannot treat batteries as a commodity any longer. Good battery maintenance is necessary to protect life expectancy and capacity of expensive battery. One key part of maintenance is record keeping. Without these records you are operating on a “gut feeling”; chemical reactions and gut feelings do not mix. Record keeping can be made virtually effortless with advanced battery management system and software.
Traditionally, the only instruments a technician has to determine the internal operation of the battery are a voltmeter, an amp meter and a hydrometer, providing a static result at best.
What is needed is a means of capturing dynamic operating data throughout the discharge and charge cycles to develop a comprehensive picture of what has happened internally in the battery.
Advancements in technology have transformed how battery performance is measured. Current measurement to and from the battery is a true indicator of battery State of Charge and hence throughput. Temperature, electrolyte level, and other parameters can help determine battery health.
Battery Management System to Reduce Battery Fleet Costs:
The step from conventional to opportunity and fast charging rates means increased temperatures within the battery and on components such as cables and connectors. How does frequent “topping off” affect the life expectancy of the battery and warranty considerations? The need is to monitor what is happening internally to the battery. Previously, tools commonly used were a volt and amp meter, a temperature gauge and a hydrometer. But it was impractical to have someone taking frequent readings on many different batteries during daily work cycles. Operators typically have different methods of working and sometimes subject equipment to conditions beyond normal parameters. Management has no way to monitor abuse and misuse other than to be there when it happens. There has been little or no accountability for improper use which can cost companies thousands of dollars per year and shorten the life expectancy of the equipment.
As service providers are trying to do more with less people, it is important to arm their technical support group with solutions to minimize time spent on data collection. Web based application with automated alerts for exceptions and reports via email allows them to focus on the customers who need immediate attention. Technical support and CSRs can prepare themselves for periodic review of customers’ fleet and help implement best practices to improve process and reduce costs.
Access Control Group, a technology leader in Fleet Management Systems, recognized the problems. After consulting with leading battery and charger manufacturers, as well as large fleet users, we set out to design devices to provide an accurate and detailed look inside the battery.
CellTrac is a non-invasive monitor which attaches to one of the main battery cables and captures crucial data during charge and discharge cycles, recording voltage, amp hours in and out, battery temperature, water level and provides alarms when out-of-bounds limits are exceeded. CellTrac has been designed to fit on top of the battery between cells where it is less susceptible to damage Typical installation time is less than 15 minutes. Data remains in memory even if power is disconnected and is cumulative for more than 1500 charge/discharge cycles. Data can be downloaded wirelessly to a laptop computer for further analysis, providing equipment managers with valuable information to monitor productivity. Standard format reports are provided as well as the provision for custom designed reports.
Each battery is assigned an ID, make, model, serial number, installation date and other pertinent battery data. Subsequent reports are generated for individual batteries, providing valuable data for tracking usage and budgeting for eventual replacements.
CellTrac can interface with fleet management systems such as Vigilant G2, Vigilant LT and AssetPro. Data can be transmitted to a web based application for global access to authorized users. The system can generate automated email alerts and reports to minimize fleet managers’ effort to monitor their fleets and still make proactive decisions.
Maximizing ROI, equipment and manpower utilization is essential to any business, now more than ever. Battery and fleet management systems measure, so fleet managers can manage and maximize performance of their mobile assets, resulting in significant savings – if proactive decisions are made based on information provided.
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