Lithium-ion battery FAQ
Lithium-ion UPSs represent a significant progression in UPS battery technology, which for decades has been dominated by valve-regulated lead acid (VRLA). Because lithium-ion batteries offer a 10- to 15-year lifespan—as opposed to their lead acid counterparts, which generally need to be replaced every 3 to 5 years—the technology offers a number of advantages.
What are the primary benefits of switching to lithium-ion UPS batteries?
The most common reason cited by our customers is the significantly longer service life. With lithium-ion, IT professionals can easily deploy lithium-ion UPSs without the maintenance and refresh challenges of those utilizing traditional lead acid batteries. The extended battery life enables users to align their UPS refresh cycles with the rest of IT stack, saving time and money spent on labor and battery replacement. This “set it and forget it” value proposition is especially conducive at sites where operations are critical yet IT resources are constrained. Lithium-ion also provides a greater cycle life (the number of charge/discharge cycles ranges from extends into the thousands, versus approximately 500 for VRLA batteries), as well as a longer standard warranty. Additionally, lithium-ion UPSs can provide more runtime in the same footprint without the need for external battery modules (EBMs). Many customers have also found the lighter weight of a lithium-ion to be an added benefit.
What are some of the downsides of lithium batteries compared to VRLA?
The primary downside is that because the technology is so new, many manufacturers have limited experience in UPS applications. However, this is changing rapidly, with successful deployments now exceeding four years.
Do lithium batteries pose a higher fire risk than VRLA batteries?
While any battery has the potential to catch fire if abused, lithium has a reputation for more dramatic ‘thermal events.’ However, in UPS applications, the presence of a Battery Management System (BMS) — which controls charge rate, voltage and temperature — makes lithium batteries less likely to enter thermal runaway than traditional UPS batteries. Additionally, the manufacturing of lithium-ion UPS batteries is not as restrictive on packaging space as other applications such as cell phone or laptop battery modules, which have appreciably constricted space. UPS manufacturers can utilize the extra space to ensure that the plates inside the battery will not short out, even in extreme conditions. As long as the battery and its packaging are designed to dissipate more heat than can be created on overcharge, the battery cannot go into thermal runaway. All UPS vendors and battery vendors are ensuring that this is the case for lithium products.
Are lithium-ion batteries more expensive?
In general, they vary from slightly more expensive than good-quality VRLA, to two times more expensive, especially when shipping costs and commissioning services are considered. In addition, Eaton requires a customer service engineer to be on site for large battery cabinet startup service, which isn’t needed for VRLA batteries. It is important to note that in the near future, when vendors start shipping battery cabinets pre-loaded with batteries, we expect the shipping costs for lithium batteries will actually be slightly less than that of VRLA batteries.
What is the cost per kWH of lithium-ion batteries compared to VRLA batteries?
The cost of lithium-ion battery systems for UPSs have plummeted 50-75% over the last four years. Today, if we compare the cost of a VRLA battery system with a monitoring system and a lithium-ion battery system with the required battery management system (BMS), the cost per kWh is comparable and, in some cases, is even less. Currently, though, the initial setup costs associated with lithium-ion – including freight from overseas to the United States and additional field service set up and commissioning costs – can drive the cost up to 1.25x the cost of a VRLA battery system. The ten year service life of lithium-ion batteries negates most of those extra costs.
Can lithium be mixed with other types of batteries (for example, VRLA)?
No, lithium cannot be put in series or parallel with other types of batteries or other lithium products.
Does Nalkar Renergy see lithium-ion fully replacing traditional VRLA batteries?
Yes, However we do believe there will continue to be places where VRLA is more appealing and expect to offer a balance of VRLA and lithium-ion solutions even as we continue investing in longer life battery solutions.
What else can a UPS system do with the addition of lithium-ion batteries?
With lithium-ion, UPS operators can play a role in helping energy providers balance power generation and consumption with the EnergyAware solution. EnergyAware enables facilities to support sustainable energy solutions, optimize the cost of powering their buildings and create additional revenue streams from their power protection assets.
I like the benefits of lithium ion for UPSs but how do I make sure it’s the right investment for me?
The longer lithium-ion battery life of the UPS—2x battery life vs VRLA—can eliminate the cost of procuring replacement batteries as well as the labor cost for in-person battery replacement. So while it is true the capital expenditure is higher for lithium ion, the lower OPEX costs can offset the up-front investment for many customers.
Are there small office/rackmount UPS lithium-ion battery solutions available now on the market?
Yes, office-sized UPSs with lithium batteries are now available. They are dramatically lighter than UPSs with VRLA batteries and the battery will typically last the entire life of the UPS.
Can I replace a VRLA battery system with a lithium-ion battery system?
Yes, Nalkar Renergy offers lithium-ion battery retrofit systems, which include new cabinets and batteries, for several of our UPS products. The field engineer will need to make minor firmware modifications to the UPS. We cannot, however, deploy a mix of VRLA and lithium-ion batteries for the same UPS system.
Are lithium-ion UPS batteries safe?
Yes, we are comfortable and confident that all the vendors’ products we offer are safe, when used with our UPS, installed per the manufacturer’s recommendations, and when their environmental requirements are observed. The battery management system (BMS) is one component which ensures the safe operation of the battery, by monitoring temperature, voltage balance, etc., and it has the ability to disconnect the battery string if conditions warrant. The other component is the design of the battery cells and battery modules. All of our vendors comply with UL1642 (Battery cell safety); UL1973 (Battery module/cabinet safety). The BMS complies with UL1973 which pulls in UL991 and UL1998 (Software safety) and UL9540A (large scale fire testing) as appropriate. We also select lithium battery chemistries that provide a balance of energy density and thermal performance.
Have Nalkar Renergy lithium-ion UPSs experienced any battery failures or fires?
At this time, no UPS manufacturer has suffered a thermal event with its lithium batteries. The presence of a BMS has been instrumental in the detection and mitigation of any anomalies. While we have seen individual batteries fail to retain a charge, these rare instances were not thermal-related and occurred only after we abused the batteries in our lab with stress testing. When the individual cells were replaced, the system operated correctly.
How is thermal runaway detected and mitigated?
The battery management system (BMS) and battery module construction handles the detection and mitigation and meets code requirements. The BMS can disconnect the string via opening the cabinet breaker.
What type of gas do lithium-ion UPS batteries give off?
Lithium-ion UPS batteries do not give off any gas during normal charging/discharging.
What is the difference between an active battery management system (BMS) and a passive BMS?
An active BMS has the ability to physically/electronically disconnect either individual batteries or battery strings if thermal or cell balance conditions require intervention by the BMS control. This would happen only after an early warning and shutdown imminent alarms and warnings are issued. A passive BMS is only a monitor. It can issue alarms, but cannot take any protective action on its own.
Why is a battery maintenance system (BMS) required when deploying a lithium-ion battery bank?
A battery maintenance system (BMS) provides a necessary level of safety against thermal runaway events.
How does the lithium Battery Management System (BMS) compare with a traditional Battery Monitoring System, like Cellwatch, for example?
Lithium battery management systems and battery monitoring systems, like Cellwatch and BTech, have the following similarities:
- Both monitor individual battery voltages and string currents
- Both provide instantaneous status of individual batteries
- Both (can) monitor battery terminal temperature and cabinet ambient temperature and can warn of possible thermal runaway conditions
Lithium battery management systems differ from Cellwatch/Btech, in the below capabilities:
- Lithium Management systems ‘manage’ the battery and can take action independently of customer interaction. For example, the BMS can disconnect the entire lithium battery string (cabinet) from the UPS if determined to be necessary and can do this without the client’s permission or acknowledgement.
- Lithium BMS systems also track and manage individual pack DC voltage balance to limit potential for development of thermal issues.
- Most Lithium BMSs lack a user-friendly HMI interface/display. Modbus information to the site’s Building Management System (also called BMS), is available for the user to implement their own data log, and storage.
- Lithium BMS tracks voltage, current, temperature, and balances voltages constantly for every battery. It communicates status changes and alarms immediately to the UPS, which can then send this info onto the client’s network via the PXGX card. But the information history is not logged in the lithium BMS.
What happens if a lithium-ion battery management system (BMS) fails?
If the BMS fails, stops operating or loses power for any reason, the cabinet or battery string will disconnect from the associated UPS. If AC power to all BMSs in a system fails, all paralleled battery cabinets will disconnect from the associated UPS.
How does a battery management system (BMS) function during a wide imbalance of the internal cabinet temperature for each lithium-ion battery?
The BMS will use the UPS charge voltage to balance the cell, similar to how we do with an equalize charge on flooded batteries.
How long is a lithium-ion battery expected to last in a UPS application?
Nalkar Renergy vendors expect 10-15-year float service life like we utilize in our UPS equipment. Both vendors offer a 3-year defect warranty and a Performance warranty of 10 years.
What is the shelf life of lithium-ion batteries before they need to be checked or charged?
Samsung’s Warranty is voided after 6 months of storage, including storage prior to shipment, but there are exceptions. Check with your Eaton representative if batteries will be stored longer, or at different temperatures than mentioned here. And, to ensure a functional battery when put into service, a voltage check of stored batteries should be done every 6 months to ensure that batteries remain functional. If the voltages are out of vendor’s limits, a recharge will be required. After recharge, the batteries may be stored an additional 6 months, and should still work properly. Eaton Service can provide the voltage check service and recharge service onsite.
Are there different recharge rates between lithium-ion and VRLA batteries?
Lithium batteries can be recharged significantly faster than traditional UPS batteries; however, keep in mind that the manufacturers limit the amount of battery charge current that the UPS can supply. During recharge, the BMS monitors not only voltage levels, but also the internal temperature of each individual lithium cell. In this manner, the system will automatically limit the charge if a cell gets too warm, which can potentially lengthen the recharge time. In general, the VRLA rule-of-thumb of “10x the discharge time to 90 percent capacity” may not apply to lithium.
How long does it take to return a lithium-ion UPS battery to 90% capacity after a discharge?
At the vendor-specified recharge currents, it should take no more than 4 hours. Very large battery systems may require longer recharge time.
Do lithium-ion batteries have recycling and/or disposal issues?
Lithium-ion batteries are disposable and, while currently not readily recyclable, new options are expected in the future.
Should recharging lithium-ion UPS batteries be delayed after a full discharge?
No. We have limited the charge current per cabinet to a level that will not add internal heating to the battery, thus we can begin recharging immediately upon return of input power.
What is max room temperature for lithium battery UPSs?
Operating temperature range: 32 to 104°F / 0 to 40°C. Note that while lithium-ion batteries will operate safely at this temperature, the lithium-ion performance guarantee specifies a narrower temperature range. That is; 18-28 degrees C to assure the full 10 year warranted life.