Getting to Know Your UPS Batteries II- Wet Cell Batteries
The second battery on our “get to know you” list is the Wet Cell, or Flooded Cell battery. UPS Systems are used in a variety of applications and, as a result, may require a wide variety of run time requirements or discharge characteristics. The battery cell is comprised of a hard plastic enclosure, typically Polycarbonate or Styrene Acrylonitrile (SAN) Plastic, lead plates and an electrolyte that allows the flow of current.
A flooded UPS battery does require a higher level of maintenance than its sealed counterpart, and because they contain spillable liquid, must be properly orientated and protected from damage by forceful movement like vibration or excessive shaking.
The main advantage of a Wet Cell UPS battery set-up is the long, extended run-time that they provide. They are also typically built to have up to a 20-year design life, though environmental conditions may shorten that lifecycle.
UPS Wet Cell batteries can also be heavy and are required to be installed in a controlled environment with proper spill containment, monitoring and exhaust mechanisms in place. Routine maintenance is required on these batteries, along with a schedule for keeping fluids filled, keeping proper venting clear and they may also require hydrogen monitoring and exhaust systems in place.
Some common hazards from Wet Cell battery mishandling are:
- Gaseous Venting- Improper venting can create an explosion hazard from the hydrogen component of this battery.
- Low Water Hazard- Not keeping the batteries properly filled with the liquid they need can cause plate damage inside the battery and a potential fire hazard.
- Burn potential- Since the water in these batteries is corrosive, it can cause potential skin lesions, burns, and blindness if a person is exposed to it. Proper clothing and handling procedures MUST BE FOLLOWED with these batteries to keep everyone safe.
When handling these batteries, proper clothing and gear must be worn as part of spill containment procedures. This includes:
- Special protection aprons
- Approved gloves
- Approved masks
Here is a sample listing of semi-annual and annual maintenance measures for UPS Wet Cell batteries. Please note this is a sample list and may vary based on individual conditions.
Sample Semi-Annual inspection includes the following:
- Record float voltage, specific gravity, and electrolyte temperature of pilot cell
- Measure and record A/C ripple voltage and current
- Record overall float voltage
- Inspect general appearance and cleanliness of battery system
- Record charger output voltage and current
- Inspect electrolyte levels
- Visually inspect jars, terminals, connectors, racks and cabinets
- Record ambient temperature
- Inspect proper operation of ventilation system
- Check for unintentional battery grounds
- Obtain specific gravity readings on 10% of string and record related electrolyte temperatures
- Add water to cells if more than ¾” below high line (NOT unless the batteries are offline)
- Measure and record cell voltage readings on 100% string
Sample Annual Inspection Includes the Following:
- All steps performed in semi-annual or quarterly inspection
- Obtain specific gravity readings on 100% of string and record related electrolyte temperatures
- Perform detailed visual inspection and condition of each cell
- Obtain inner cell connecter resistance readings on 100% of string and torque as needed
- Clean and re-secure all inner cell connections, as necessary (up to 20%)
- Inspect rack or cabinet integrity
- Clean and neutralize, as applicable
- Review spill control and safety equipment (spill kit, neutralizer, PPE, spill containment systems, hydrogen detection, signs)