Batteries are considered a consumable, much like the brakes on your car or the fuel in your gas tank. Over time the batteries lose their ability to take a full charge and therefore typically every 2-5 years, depending on the battery type and quality, the battery pack inside of an UPS should be replaced.

The battery chemistry considered standard in the UPS market is the rechargeable, non-hazardous and non-spillable Sealed-lead Acid (SLA), specifically the Valve-Regulated Lead Acid (VRLA), Absorbed Glass Mat (AGM) type. This is due to the chemistries ability to support high-discharge applications while offering a long-term storage life, both standard requirements of UPS applications. The compromise of using the SLA chemistry is that the battery is bulky and heavy due primarily to its low energy-density. While just about every other type of rechargeable battery offers a higher energy-density, none offer the long-term reliability or safety of the VRLA/SLA chemistry.

Additional Battery information includes:

Most UPS applications require a battery capable of handling high-discharge rates while providing a long storage life because the batteries could go for several months or years without ever being used and then instantly have to provide 100% of the energy for that application. Sealed Lead Acid batteries have a remarkably low self-discharge rate when compared to other commercially available chemistries and can sit on float-charge for years without losing capacitance (an effect known as “voltage depression” or more commonly, but incorrectly, referred to as “memory”).

The downside to this ability to sit relatively inactive for years and then immediately provide 100% performance is a relatively low energy density, meaning the batteries are bulkier and heavier than other battery chemistries. Also, care should be taken to not exceed the manufacturers recommend charge rate, meaning it can take up to 6-12 hours to recharge a SLA battery, regardless of capacity. Expedited recharge rates can harm a SLA battery. These considerations, while sometimes frustrating, have been accepted by the UPS market for decades.

Our Uninterruptible Power Supply (UPS) products provide two important functions, both of which are equally important to today’s war fighter:

  • To act as a power conditioner, and
  • To provide battery backup in the event of a power loss

If the UPS malfunctions by way of the circuit board, it is seen as a failure of the entire UPS and therefore the vendor providing and supporting the UPS. Similarly, if the battery pack does not perform to the runtime and lifetime specifications that the design engineers specify (and that the end-user’s expect) it is seen as a failure of the entire UPS.
Therefore, we work hard to ensure the batteries installed in all of our UPS’s meet the quality requirements of our customers, because the batteries are as an important component in our UPS as the circuit board.

To meet the runtime and lifetime requirements as defined-by and required-of our customers, a factory-supplied battery pack undergoes performance-based quality testing prior to final assembly. These processes then make factory-supplied battery packs superior to other identically-looking battery packs in both individual runtime and product life. This testing unfortunately takes a lot of time and is considered labor-intensive.

In all likelihood the capacitance of the battery pack in your UPS has been chosen to meet a specific requirement. Normally, a battery of known capacity will last longer on a lower wattage than on a higher wattage draw application, so both battery capacitance and wattage draw should be taken in considering when designing the battery backup runtime of your system.

Most of our UPS’s are designed to provide at least 4 minutes of battery backup runtime at 100% load. Not all systems are designed to run the UPS at 100% load, so your runtime will vary depending again on battery capacitance and wattage draw. Where your load cannot be supported only by the battery pack in our UPS’s, we offer additional battery backup trays which house additional battery packs and plug into the back of our UPS’s.

Regarding charge time, most SLA battery manufacturers recommending charging their batteries at a fixed charge rate ratio regardless of capacitance. The charge current varies depending on capacitance, but the ratio of charge current to capacitance is always the same. This means that no matter the capacitance of the battery pack, large or small, the maximum amount of time it’s going to take to charge your SLA battery pack is always going to be a conservative 6-12 hours.

There are varying opinions, but most SLA chargers follow a two-stage charging algorithm following by float charge. The last 10% of capacitance is the hardest to put back into the battery, meaning the first 90% of the charge cycle can take as long as the last 10% does.

For additional questions, including more detailed explanations and information:

NOVA Power Solutions advises using only factory-supplied battery packs with all of our UPS products. Failure to do so could void your warranty, cause harm to yourself, and/or damage the unit.