It's easy to set the stage for battery reliability if you know the requirements.
Performance and reliability are functions of battery condition in most backup power systems. All of the maintenance effort in the world has little meaning without proper installation. You can easily cut battery life in half or turn maintenance into a nightmare with just one installation mistake.
Selecting the right battery for the job is the first step in a stationary battery installation. Lead acid batteries are the most popular choice in the United States, although nickel cadmium is appropriate for some specialty applications. The battery industry divides lead acid batteries into two categories: flooded and sealed. Most experts refer to sealed batteries as valve-regulated lead acid (VRLA). Some people consider them maintenance-free, but that's not necessarily true. Table 1 (below) shows a brief comparison of the considerations for flooded and VRLA batteries. The installation issues are similar for both types.
Things to consider. Once you've selected your battery, be sure to address the following installation issues to ensure easier maintenance and maximum reliability.
The battery area should be centrally located for easier distribution of power. A clean, dry area improves safety and reliability of the entire system. A flooded battery requires a separate battery room to meet various fire and building codes. You can install a VRLA battery in a room with other equipment and employees, but this area should be restricted. If it becomes a storage area, you'll increase fire and safety risks. You must provide adequate space around the battery system to allow for maintenance tasks.
Temperature control Temperature has a major effect on the life expectancy and performance of any battery system, as shown in Table 2. Considering the shortened life expectancy of a battery at high temperatures, it may be easy to justify installing the battery in an air-conditioned area.
Lead acid batteries have a maximum storage time of six months at temperatures between 65°F and 85°F. At the end of that time, you must either install the battery or give it a freshening charge. Try to schedule the battery arrival at the site as close as possible to the installation date.
Transportation and receiving
Batteries are quite fragile, so you should inspect them for freight damage upon receipt. Verify that the water level in flooded batteries is between the level lines and that none of the plastic containers or covers are broken. Inspect to make sure no posts have been damaged in transit.
Seismic and floor load
Verify that any rack or cabinet in the battery room meets the seismic codes for your area. Many people do this for racks or cabinets that hold batteries, but then forget about nearby racks or cabinets that could fall onto the batteries. Don't make that mistake. Check the total weight of the installed system and verify it's within the floor load limits. You must consider the safety measures involved in transporting battery cells in and out of the area. A stacked VRLA battery can weigh as much as 1,000 lb per sq ft.
Because batteries are “chemical engines,” they can explode and cause serious injury. Whether you're installing the battery yourself or contracting the work out, everyone involved must be familiar with all the battery safety issues, manufacturer's instructions, tools and test equipment, and IEEE installation recommendations. Individuals who work with batteries must use the appropriate personal protective equipment (PPE) and other safety equipment. You'll at least need the following items:
Safety glasses with side shields or chemical goggles.
Emergency eye wash provision.
Emergency spill containment and response equipment.
Water and bicarbonate of soda.
Insulated tools (avoid metal chains and jewelry).
Apron and gloves.
Other items that may be appropriate include a battery spill kit and a battery acid containment system. Once you've addressed all of the preceding issues, you can start the installation.
Assemble the battery rack according to manufacturer's instructions and anchor it to the floor. Verify that dimensions, aisle widths, and clearances are adequate for maintenance access. Place cells onto the rack or cabinet, starting in the center of the bottom row and working outward. Be careful, though, because you can damage the posts if you use them to carry the battery. You'll probably need a mechanical lift to get the cells from the pallet onto the rack. Follow the manufacturer's recommendations for sliding cells on a lifting table or rack, but don't use oil or grease that isn't specifically approved for that purpose. Note that on many seismic applications, you must install spacers between each cell.
The battery manufacturer should supply a layout or connection drawing. Make sure you set the cells so they connect in a series — the positive of one cell connects to the negative of the next. You can verify that all cells are truly connected in series by reading the voltage of one cell, multiplying this by the number of cells in the system, and comparing this to the overall voltage. A 4V discrepancy indicates one cell is installed backward.
Neutralize any spilled acid on cell covers with bicarbonate of soda, and remove any grease from the cell post with a rag or paper towel. Don't use degreasers or solvents.
Polish the post and intercell connector with Scotchbrite, a brass bristle brush, or approved equivalent. If in doubt, ask the manufacturer. Don't use a wire brush, as this may damage the protective lead plating on the copper connectors.
After applying a light coating of NO-OX grease or a manufacturer-approved equivalent to the post and intercell connector, assemble and install the intercell connectors and bolts, and torque them according to the manufacturer's instructions. But be careful: Bolt torque is always in in.-lb, not ft-lb. Once you've finished the installation, read and record the intercell connector resistance from one cell to the next using a micro-ohmeter. This verifies that all intercell connectors are properly installed. You'll need this baseline data for all future maintenance checks.
You can now connect the battery to the system and start the freshening charge. Battery manufacturer's instructions give voltage and time values to assure the battery is fully charged, and to compensate for any charge lost during storage or transit. After the freshening charge is completed, adjust the battery to its proper float voltage. This is usually 2.25V per cell for VRLA and flooded calcium and 2.17V per cell for antimony type. Refer to the manufacturer's instructions. Read and record all individual cell float voltages, specific gravities, intercell connector resistances, and internal cell resistances. You'll need all of these readings for future maintenance.
The IEEE has detailed installation and maintenance procedures for flooded and VRLA batteries (Sidebar below). IEEE Standards Committee 29 has reviewed and updated these procedures and will continue to do so as technology moves forward. Proper installation ensures fewer operational and maintenance problems, while enhancing reliability and lowering the total cost of ownership.
Blohm is the field training manager, EnerSys, Inc., Reading, Pa.
Sidebar: Applicable IEEE Documents
IEEE-484: IEEE Recommended Practice for Installation Design and Installation of Vented Lead-Acid Batteries for Stationary Applications
IEEE-1187: IEEE Recommended Practice for Installation Design and Installation of Valve-Regulated Lead-Acid Storage Batteries for Stationary Applications
IEEE-450: IEEE Recommended Practice for Maintenance, Testing, and Replacement of Vented Lead-Acid Batteries for Stationary Applications
IEEE-1188: IEEE Recommended Practice for Maintenance, Testing and Replacement of Valve-Regulated Lead-Acid Batteries for Stationary Applications