Just as different types of solar panels change how a solar power system is operated and maintained, multiple types of batteries will affect the performance and maintenance of a solar-plus-storage system. If someone is looking for a cheap and durable energy storage product, lead-acid batteries might be the way to go, but that requires some more maintenance. Lithium-ion battery storage systems are a mainstream option for owners of solar power systems that require a maintenance-free approach, but they are not suitable for extreme environments.
Different levels of battery maintenance work may affect which energy storage system is used for solar + energy storage. The following will explain the maintenance requirements of several common battery energy storage products used in the solar power generation industry: lithium-ion batteries, lead-acid batteries, nickel-cadmium batteries, flow batteries.
(1) Lithium-ion battery
According to Brent Harris, founder and CTO of Eguana Technologies, lithium-ion batteries are the energy storage product of choice for most solar power applications because of their high density, low maintenance, and low cost. Lithium batteries are not suitable for some specific applications, such as extreme temperature ranges or where long-term energy storage is required, and other batteries may be more cost-effective. The biggest maintenance item for lithium-ion batteries is the degradation rate. Just like cell phone batteries, lithium batteries used in energy storage systems in solar power facilities are severely depleted after a certain number of charges and discharges. Developers must plan for this degradation rate. The two most common types of lithium-ion batteries used in solar-plus-storage projects are lithium iron phosphate (LFP) batteries and lithium nickel manganese cobalt (NMC) batteries.
(2) Lithium iron phosphate (LFP) battery
Lithium Iron Phosphate (LFP) batteries are safe and durable batteries. Since no cobalt is used, there is no thermal runaway (fire) problem, and no ventilation or cooling measures are required, so it can be easily installed indoors, making it ideal for residential energy storage applications. According to Sonnen Corporation, manufacturer of lithium iron phosphate (LFP) batteries, the batteries are ideal for stationary energy storage applications, especially when the batteries are required to be cycled daily for solar power self-consumption optimization and grid-connected services.
Lithium Iron Phosphate (LFP) batteries require no more maintenance, but where they are installed can affect performance. Lithium batteries are required to use a battery management system (BMS) that automatically monitors each battery's temperature, state of charge, cycle life, etc. to maximize performance. As long as the energy storage system is installed in an acceptable temperature range and altitude, maintenance measures are not required.
"As long as lithium iron phosphate (LFP) batteries are stored and installed in a location that matches the environment in which the product is deployed, regular maintenance is not required," said Carlos Restrepo, Sonnen's vice president of technology. It's important. Batteries don't have to be prepared for seasonal temperature changes."
Brad Hansen, CEO of EnSync Energy, said: “Lithium Iron Phosphate (LFP) batteries can be subject to threats from overcharging, high temperatures, and even physical damage and stress, so safety needs to be maintained. When batteries are used in or near living spaces, Choosing the safest battery as an essential part of the system is an important guiding principle."
(3) Lithium nickel manganese cobalt oxide (NMC) battery
Lithium Nickel Manganese Cobalt Oxide (NMC) batteries are durable and very safe as long as they are monitored by a battery management system. By adding elements such as nickel and manganese to the battery chemistry, the battery can store more electricity than other types of lithium-ion batteries.
Like other lithium batteries, lithium nickel manganese cobalt oxide (NMC) batteries require no major maintenance. A battery management system (BMS) will monitor the voltage, current and temperature of the battery to ensure safety and operating life.
Eguana's Harris said, "Extreme operation can shorten the life of the battery, and the monitoring system records the operation through the battery management system (BMS) to notify warranty claims. In any potentially unsafe operating conditions, the battery management system (BMS) Shut down the system.” The company’s battery energy storage system uses lithium nickel manganese cobalt oxide (NMC) batteries from LG Chem.
Lithium nickel manganese cobalt oxide (NMC) batteries can be used in winter as long as the safe temperature range is confirmed.
"If seasonal energy storage systems are required, they should be stored indoors," Harris said, citing Canadian winters as an extreme example.
(4) Flow batteries - especially zinc bromide (ZNBR) batteries
Zinc bromide (ZNBR) flow batteries (most commonly made by Primus Power) are well suited for large-scale long-term energy storage systems. Flow batteries use two chemical components dissolved in a liquid separated by a separator to provide electrical charge. Zinc bromide (ZNBR) flow batteries have zinc bromide salts dissolved in an electrolyte. The battery technology used by Primus Power is slightly different from conventional zinc bromide (ZNBR) flow batteries, and its separator does not require cleaning or replacement. Primus Power uses storage tanks to store electrolyte, and its flow batteries have infinite charge-discharge cycles without performance degradation. Flow batteries generally require very little maintenance.
Flow batteries are like fuel cells, so they're just boxes with electronics and electrolyzers. Primus says its Energy Pods products only require annual maintenance visits from certified operations and maintenance (O&M) service technicians to perform routine inspections, replace air filters, and top up electrolytes. Flow batteries can be used in winter and can be installed in very cold conditions.
“We monitor all deployed batteries 24/7 to ensure proper operation and proactively address any potential field issues. This data is also available to the owner’s O&M provider in real time,” said Primus Power’s CCO Jorg Heinemann. Batteries are designed to last as long as, if not more, solar power plants with energy storage solutions, and do not require additions or regular replacements like lithium-ion batteries.”
(5) Lead-acid battery
It is well known that lead-acid batteries are reliable and inexpensive. Their grid-like structures are immersed in acidic electrolytes, whose electrolytes may require long-term replenishment. Batteries are heavy due to the material and some must be installed in ventilated areas. Their operation and maintenance requirements are well understood at this point, so they are ideal for most solar+storage applications and should be stored in a dry location with moderate temperatures.
The terminal connections of lead-acid batteries should be checked several times a year to ensure they do not loosen over time. Flooded lead-acid batteries need to be replenished with distilled water regularly. Fiberglass separator (AGM) batteries and gel lead-acid batteries are hermetically sealed and therefore do not require replenishment of electrolyte.
If the lead-acid battery is not used temporarily, it needs to be stored properly. Trojan Battery says lead-acid batteries self-discharge over time and need to be charged to a minimum level even when not connected to a load. This self-discharge rate varies with temperature, with high temperatures increasing the discharge rate and low temperatures decreasing the discharge rate.
Trojan Battery experts said, "The maintenance required for lead-acid batteries is not very difficult, but the maintenance work is large. This is especially true for lead-acid batteries that need to be filled with water. When adding distilled water to replenish the electrolyte level, Acid will be exposed. We recommend that battery maintenance staff wear safety glasses and gloves. If customers are concerned with battery maintenance, they can ask for outside help to complete this task.”
(6) Nickel-cadmium (NiCd) battery
Nickel-based batteries are ideal for remote off-grid installations in demanding applications where reliable backup power is required and regular maintenance is not possible. They work well in extreme temperatures and deep discharges.
EnerSys said that, similar to lead-acid battery maintainers, nickel-cadmium (NiCd) batteries should be regularly inspected and replenished. Because nickel-cadmium (NiCd) batteries can operate over a wide operating temperature range, you don't have to prepare for extreme cold in winter, but batteries should not be stored below -22°F. Nickel-cadmium (NiCd) batteries can be stored (not connected to a load) for up to 12 months as long as the environment is dry and within the proper temperature range.
Jay Frankhouser, director of business development and marketing for backup power at EnerSys. “Voltage readings and electrolyte level checks on NiCd batteries can be easily done by the battery system owner. Adding water can be done by the owner, but they will need to take the safety precautions outlined in the installation and operating manual. While capacity testing or other electronic Testing should be done by qualified technicians."