By Sean Silvey
Lead acid batteries are everywhere. While they are a cheap and reliable energy source for our cars and generators, they also require a lot of maintenance to keep them at full capacity.
Lithium ion batteries, on the other hand, need less maintenance but cost more up-front. They are lightweight and have a high energy density. They can also be fully depleted without an issue, which is important with variable solar energy since the battery won't always be charged fully.
With the growth of renewable energy, battery storage levels are going to play a significant role now. In fact, regulations on Energy Storage Systems (ESS) were even added to the National Fire Protection Association's (NFPA) National Electrical Code (NEC) in 2017, and updated again in the 2020 NEC.
Batteries can be sensitive to their surroundings. Taking the steps to maintain proper storage and health of the batteries can extend their lives. Three common issues seen with batteries include:
Batteries work best between 15 and 35 °C, and need a charge controller to receive a specific amount of current. At higher temperatures, internal corrosion in the battery is increased. To offset this, store them in shaded and ventilated spaces.
At colder temperatures, the electrochemistry in the battery is slowed - that means it cannot deliver as much current (you've probably experienced this with your car battery not starting when it's cold outside). A battery heater or thermal insulation can help offset this problem.
Terminal corrosion occurs when hydrogen gas is released from the acid within the battery and reacts with other substances. Electrolyte leaking from overfilling with water, or even overcharging, can cause corrosion on the battery terminals. As mandated in 706.31(A) of the NEC, antioxidant material can prevent and remove corrosion (always follow the manufacturer's recommendations).
With lead acid batteries, small sulfate crystals can build up on the terminals. This is also known as sulfation, if the state of charge (SOC) is too low. It's critical to ensure a high SOC or the sulfation will reduce battery performance. To handle this issue, technicians need to watch for when the SOC drops too low. An alarm with a visual and audible notification can alert technicians of a low SOC (50 percent for lead acid batteries). If the charge does drop too low, a desulfating battery charger can be used to dissolve the sulfates with high-frequency electronic pulses.
Tools to diagnose battery health
The first step to keeping batteries running - at maximum capacity - is ensuring that technicians know the internal health of the battery. A battery analyzer is the best tool for maintenance, troubleshooting, and battery performance testing. It can be used with individual, stationary batteries as well as critical back-up battery banks.
A battery analyzer is turned to milliohms, then connected to the negative and positive terminals through test leads, at which point it will simultaneously display the battery voltage and internal resistance. Turning the analyzer's dial to discharge mode allows it to measure capacity loss, meaning the battery stores less charge; in this mode, the analyzer reads the battery's voltage multiple times until it goes below the cutoff value, where it would cause damage.
Temperature is critical for batteries to work properly. An IR thermometer or contact thermometer will help pinpoint where an issue is, especially if the facility has a bank of backup batteries. If a battery is overheating, the threshold setting on the thermometer will give a warning that the battery failed and exceeded the temperature set.
A hydrometer can also be used to show a battery's SOC by measuring electrolyte-specific gravity through the relative density of liquids.
While lead acid batteries have a low entry cost, their ongoing maintenance costs are higher than for lithium ion. It's a smart practice to add the batteries to your preventive maintenance plans. This will help stay in control of weekly cleaning, testing, and top-up tasks to ensure the batteries remain at peak capacity.
In facilities with uninterruptible power supply (UPS) systems, incorporating ongoing battery maintenance into the regular schedule makes a huge difference. UPS systems provide backup power for plant emergency and safety shutdown systems, plant alarms, emergency lighting, generators, fire control, and even hospital life-support systems.
A UPS system can convert stored energy from the battery into AC power to keep plant systems running, even if there is an abrupt interruption in power. During normal preventive maintenance checks, a power consultant should begin by going through the whole facility looking for hotspots, loose connections, and heat dissipation.
If no issues are found, focus turns to the UPS system itself. This involves thoroughly checking over the whole system, starting with the battery charger and individual cell voltage readings. Using a digital multimeter, an insulation meter, a clamp meter, a portable oscilloscope, an mA loop calibrator, and a thermal imager, every aspect of the UPS system is inspected to make sure they're running at peak performance. The consultant's job consists of about 90 percent scheduled maintenance and 10 percent emergency responses. Focusing on regular battery system checks means that customers can depend on their UPS systems without needing the knowledge and expertise to maintain it themselves.
The battery path you choose will depend on your facility's priories and costs. As costs continue to decline for lithium ion and other non-lead acid batteries - and their use in solar and wind energy continues to grow - batteries will increasingly become an essential part of facilities.
Sean Silvey is a Product Specialist for Fluke Corporation, a worldwide company that manufactures, distributes, and services electronic test tools and software.