For decades, lead acid has reigned as the predominant battery for uninterruptible power systems (UPS). But lithium-ion is increasingly proving to be a worthy contender whose array of advantages just might revolutionize UPS battery technology. One of the most significant benefits is the level of reliability afforded by the newcomer. In fact, lithium-ion battery failure in UPS applications is almost non-existent. By comparison, 55 percent of unplanned outages and one-third of all UPS system failures are caused by lead acid battery failure, according to a Ponemon Institute Research study.
Why is there such disparity between the two battery types? Consider these qualities of lithium-ion:
1. They offer a longer lifespan — Depending on the chemistry used, lithium-ion batteries boast a lifespan of eight to 15 years, which not only enhances reliability but also represents a huge savings in replacement costs over lead acid batteries, which have to be replaced every four to five years. Lithium-ion’s extended lifespan eliminates constant worry over whether your lead acid UPS batteries will perform when you need them most.
2. They also afford a longer life cycle — A lead acid battery typically operates for about 200 discharge cycles, meaning the battery can be depleted to 50 percent of its rating and recharged back to 100 percent a total of 200 times before it dies. But lithium batteries provide 500-7,000 discharge cycles before battery replacement is necessary. In addition, lithium-ion batteries have a lower self-discharge rate when not in use, boosting their shelf life.
3. They recharge faster— Lithium-ion batteries fully recharge in about two hours. By comparison, lead acid batteries typically require about 24 hours. As a result, a lithium-ion-powered UPS is better equipped to handle multiple outages in a short time period, with the battery able to recharge faster and provide full UPS ride-through for each outage.
4. They can withstand higher ambient temperatures — Lithium-ion batteries are able to operate safely at temperatures of 86°F (30°C) — nearly 10 degrees higher than lead acid. This can be especially advantageous in data center environments by enabling cooling costs to be dramatically reduced. Lithium-ion batteries are also less sensitive to temperature changes than lead acid, with their lifespan not shortened by fluctuations in cold and heat.
5. They include an internal Battery Management System (BMS) —Most Lithium-ion UPS batteries feature a built-in Battery Management System (BMS) that monitors the state of charge and cell temperature, providing accurate information on the battery cell and pack health. The BMS ensures that cells remain balanced and within their voltage limits.
6. They utilize the preferred chemistry for UPS applications — All lithium-ion batteries are not created equal; there are multiple “flavors” of lithium that are used in different types of devices, with lithium-iron-phosphate (LFP) representing the preferred chemistry for UPS batteries. Cobalt-free, the batteries provide impressive power capacity without storing as much energy as other cobalt-containing cathodes used in other chemistries, making them safer for flammability concerns.
Reliability isn’t the only factor that makes lithium-ion a standout for UPS applications. In our next installment in this series, we will delve deeper into another important advantage extended by the battery technology: their small weight and footprint.
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