When it comes to UPS batteries, there are two rudimentary — and yet somewhat contrasting — truths. First, batteries are the heart of any UPS system. And second, they can be inherently unreliable.
Because of that, it is recommended that you deploy multiple strings of batteries to ensure your UPS performs as expected during a power outage. Studies have shown that battery failure is one of the leading cause of load loss. Likewise, it has been well documented that equipping a UPS with multiple battery strings in a parallel configuration can dramatically reduce that risk.
In recent years, there have been improvements in battery technology that have reduced the threat of unexpected failure, including advanced charging techniques, software management, and firmware upgrades that add intelligence. Yet none of these capabilities can completely eliminate the risk of battery failure. One of the simplest and most cost-effective ways to prevent the loss of a critical load during a power outage is to equip your UPS with at least two battery strings.
A string of UPS batteries is often compared to a string of holiday lights; if one fails, the entire chain goes dead. Although one faulty UPS battery doesn’t necessitate having to replace the entire string, determining which battery has failed can be challenging. Even more, it is crucial to test the cell level health of the entire string in order to identify if other units have been damaged by strain from the faulty battery. The most effective plan of attack is to spot-replace bad batteries that are less than two years old and swap out the entire string between the fourth and fifth year. Continuous battery monitoring, coupled with scheduled maintenance, is the only way to identify bad batteries early enough to complete a spot replacement.
To reduce the risk of unexpected load loss from a failing UPS battery, it is wise to invest in a UPS that offers the option of multiple battery strings. By tying together battery strings in a parallel configuration, it eliminates a single point of failure in the UPS. For example, consider a UPS system that has 20 batteries connected in a series. If a problem occurs in any of those batteries, the entire string will likely fail, taking the UPS — and your critical load — down with it. Yet by adding another 20 batteries in a parallel configuration, if either string fails, the UPS has the capacity to continue operating for a limited time on the other string until either a backup generator comes online or the connected load is safely shut down.
Although the upfront investment in additional battery strings will run more than a single string, consider the alternative: for Fortune 1000 companies, the average total cost of unplanned application downtime per year is $1.25 billion to $2.5 billion; the average hourly cost of an infrastructure failure rings in at $100,000 per hour; and the average cost of a critical application failure per hour is $500,000 to $1 million. Indeed, the dollar amount required to bolster availability through the purchase of additional UPS batteries is dramatically less than the price tag associated with potential downtime, which can include equipment damage, loss of application services, data loss, damage to reputation and loss of productivity, among other costly consequences.
In our next installment of this series on UPS batteries, we will break down one of the main factors impacting battery life and longevity: battery temperature.
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