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What’ s your FTTH backup battery strategy?
Lead-acid battery-based UPS systems cost too much and underperform. It’ s time to talk about lithium-ion, says David Atman( right), president, Lindsay Broadband Inc.
Fibre to the home( FTTH) is an increasingly viable option for delivering services to new and existing cable TV subscribers. As the numbers have grown, so too has concern about the new demands that FTTH places on network providers, such as ensuring power to the optical network unit( ONU).
The challenges posed by potential power outages are compounded by operational limitations of lead-acid based FTTH uninterrupted power supply( UPS) systems. An alternative lithium-ion based system enables improved technical operations and much better total cost of ownership.
FTTH and UPS Systems These were once more limited challenges. Because of the resilience of the hybrid fibre / coax( HFC) network, the cable industry has for the most part looked to FTTH as a niche play. Standardised in 2010, the RF over Glass( RFoG) network design was seen as a good greenfield solution. However, with a slow economy, for many years there just wasn’ t much new construction.
Then the economy picked up, creating more greenfield opportunities. In addition, FTTH is gaining support in some quarters for rebuilds. One North American operator, for instance, has announced plans to pull fibre to all of its 8 million subscribers. Whether or when that happens remains to be seen, but momentum for RFoG and passive optical networking( PON) is strong all the same. Between September 2016 and September 2017, new FTTH‘ homes marketed’ hit a record 4.4m in the US, according to the Fiber Broadband Association.
With more deployments comes increased attention to the challenges of FTTH. One factor is fibre itself. Subscribers don’ t necessarily expect other parameters to improve when their data service becomes faster over an existing( DOCSIS) infrastructure, but with FTTH, it’ s different. Once fibre is drawn to the house and an ONU is installed, the game changes.
The baseline expectation is that with fibre
you get faster connection, higher throughput and 24 / 7 service – with no interruptions. If the lights go out, subscribers expect the ONU to stay on.( Regardless of whether they have back-up power for routers or other CPE devices.)
That’ s a reasonable expectation. After all, the ONU is a fibre-optic node. It just happens to be at the customer premises. So, it needs backing up. The question is how?
For most service providers, the‘ lights-out’ strategy for FTTH involves on-premises UPS systems that use lead-acid batteries. Yet that’ s becoming an issue. Service providers that we know have shared several areas of high-level frustration with existing solutions. We hear that:
• They are bulky and hard to work during installation and service calls
• Their battery life and runtime are both too short
• Poor design leads to connectivity problems, and
• Their total cost of ownership is climbing out of control
Adding to the frustration is the impression that these battery-backup UPS systems have failed to modernise. While rechargeable batteries have undergone change in consumer electronics and other innovative applications, the UPS market segment has been less dynamic.
The original rechargeable battery cell, designed more than 150 years ago, used two lead-based sheets( positive and negative electrodes), a separating element and a sulphuric electrolyte. In the 1970s came the valve regulated lead-acid( VRLA) battery, which sealed the electrolyte in new ways, promised minimal maintenance and enabled operation in any direction. Today’ s typical FTTH UPS backup battery is VRLA, but that original design remains largely in place.
Lead-acid batteries are well-established and good at delivering high-surge currents, but they have limits. They are too big for small electronics, and while they do well powering automotive starters, they are impractical for powering cars directly. What consumer electronics and electric car manufacturers use instead is the rechargeable lithium-ion battery.
Lithium-ion vs. Lead-acid Lithium-ion technology first emerged in the 1970s and went into production two decades later. Like lead-acid, these batteries also consist of electrodes and an electrolyte, but use lithium instead of lead. In addition to being lightweight, lithium is highly reactive, so it can store a lot of energy. The net outcome is a low-weight battery with high-energy density.
Consumers may be aware of lithium-ion in smartphones or laptops or hybrid cars. They may also recall reports of heat-related failures and recalls. But this powerful technology, which is now subjected to multiple layers of protection in manufacturing, is now impacting more traditional markets, too. Motorcyclists, for example, can switch out a lead-acid for a lithium-ion battery, dropping from 12 pounds to a little more than 2 pounds in the process. The lithium-ion motorcycle battery also comes with a longer warranty, provides more powerful starts, charges faster and has a better discharge rate.
In markets where lead-acid batteries are competitively priced, lithium-ion batteries are more expensive.( This is not the case in the FTTH UPS market, as we note below.) One reason is that lithium-ion batteries become inert if they are completely discharged and, as a result, require an on-board computer to manage the charging process.
But maybe lithium-ion batteries should command a premium. Consider these advantages:
Weight. Lithium-ion is much lighter than a lead-acid. A standard VLRA battery used by a
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