Uninterruptible Power Supply: All You Need To Know.

An uninterruptable power supply (UPS) or battery backup is a backup solution that provides power whenever your regular power source fails or drops below a set standard of voltage. A UPS solution allows for the safe shutdown of connected equipment. UPS devices also provide protection from power surges.

There are three major types of UPS system, each providing various levels of protection.

Online UPS system

This UPS system provides the most secure form of power when mains power is available and when there is a power outage. The inverter constantly runs and powers the load using either a rectified mains power or generator or connected battery set. An automatic transfer switch monitors the output from the inverter and automatically transfers the load to the raw mains power supply if the inverter output collapses during an UPS overload, short-circuit or fault condition.

Line interactive UPS system

The next step down in uninterruptible power. This UPS has an automatic voltage regulator (AVR) to which the load is connected and supplied a stabilised and filter AC waveform. The battery is charged by a circuit connected to the input AVR and an inverter is live but not powering the load directly. The inverter takes over when the mains power supply fails or fluctuates outside the operating range of the AVR.

Standby/Offline UPS system

Offers basic power protection and operates in a similar manner to a line interactive UPS. A filtering circuit provides some protection from electro-magnetic interference (EMI), spikes, transients, and surges. The off-line inverter powers up when there is a power outage lower than a line interactive UPS system with no automatic bypass. The battery backup is typically limited to an internal battery and this UPS type is available from 250VA to 1kVA.

A UPS system normally use batteries for their backup power. When it comes to UPS the typical battery debate exists: Lithium-Ion vs Lead Acid.

Let’s look at the case for Lithium-Ion batteries.

The key advantages for Lithium-Ion batteries are as follows:

• Energy density: Lithium-Ion batteries can hold a much greater volume of electricity, up to ten times more electricity that Lead Acid batteries.
• Battery memory: This can occur when a battery is repeatedly cycled (charged and discharged) before all of its stored energy is released. This effect can cause a battery to collapse quickly due to memory effect and therefore not provide the runtime expected. The only solution being to completely discharge the battery before the next recharge and usage. Lithium-Ion batteries have no memory, so this isn’t an issue for them.
• Recharge Time: The recharge of a lead acid battery is a non-linear curve. A rule of thumb is for the battery to recharge to 80% within 24 hours, dependent upon the size of the charger used. Lead acid batteries are therefore ideal for standby applications where there is infrequent usage. Lithium batteries are far more tolerant of rapid charge/discharge cycles and recharge faster.

The key advantages of Lead Acid batteries

• Less-Flammable: Lead acid batteries are exothermic on recharge and give out heat when charging as the cells generate heat from the chemical reaction going on inside them. Thermal runway is unlikely in a lead acid battery and the primary flammable material (the plastic case) can be made from flame retardant materials. In a lithium-ion battery, the lithium itself is highly flammable when exposed to air.
• Easier to recycle: Lead Acid batteries are easier to recycle owing to their less flammable nature.
• Pricing: Lithium-Ion batteries cost more than Lead Acid batteries.

Lead Acid batteries are the more common choice for uninterruptible and backup power systems. They are more cost-effective to purchase, as well as easier to recycle. Lithium battery installations require less floorspace, have faster charge/discharge cycles, & design lives have a 20—30% greater capital outlay.  They are also other installation expenses to consider including environmental monitoring and fire suppression. Both Lead Acid and Lithium-Ion batteries are both viable options. Your choice will ultimately depend on your unique needs. A good question to have in mind is how often you expect your UPS battery to discharge. In a typical server room or data center the UPS battery will either provide short term power as a standby power generator starts up or a longer runtime to either ride through long duration power outages or provide enough time for a controlled shutdown. The fast recharge/charge advantages of lithium only come into play if the site experiences frequent power outages and/or is looking to export excess stored energy to a national grid to benefit from feed-in tariffs.

As experts in Solar Power, we can advise you in what battery choices would provide you with the most value for your Solar Power solutions!

Get in touch with us today: Contact Us | Connected House | Connected House