Saft: Li-ion technology takes telecom backup power to the next level

Effective, reliable backup power is essential for the telecommunications industry to maintain continuity of service as networks need to evolve to meet the demands of the ‘always on’ world that now includes cloud computing and high bandwidth data streaming, et cetera. Saft has used its extensive experience in the global telecoms industry to develop a broad portfolio of advanced, specialised battery solutions suitable for wireless or wireline installations, indoor or outdoor, on-grid or standalone, in very hot or cold climates, urban settings or remote hard-to-access locations.

TowerXchange: Please introduce Saft - where do you fit in the telecoms infrastructure ecosystem?

When network stability is low, customers need a solution with good cycling capabilities and good chargeability. When network stability is high, they need solutions with float charging capability and a long service life. Saft offers backup solutions for periods from 30 seconds to over one day.

TowerXchange: What is your installed base and experience in emerging markets, particularly Africa?

Saft has extensive experiences and references in various African countries such as Algeria, Nigeria, Cóte d’Ivoire, Senegal and Gabon.

In Nigeria, Saft’s specialised Sunica.plus nickel-based batteries provide the energy storage at the heart of Eltek Valere’s innovative hybrid telecom power systems, combining batteries with diesel generators, that have been rolled out to 80 mobile telecom sites across the country. These co-location sites are provided for Nigeria’s wireless operators on a fully managed leased basis, and QoS (Quality of Service) is absolutely vital in this competitive market.

TowerXchange: Batteries have an unfair reputation as a commoditised piece of equipment, the selection of which rarely attracts the attention of C-level decision makers - why should CTOs, CFOs and CEOs take an interest in which batteries are used at their cell sites?

Mobile network operators place a major emphasis on ensuring consistent quality of subscriber service. The design and management of backup power systems to maintain continuity of power, in the event of an interruption to the main site power supply, is therefore a vital issue. When the main power supply fails, the backup battery must be able to perform. My view is therefore that battery selection is a critical element in the success of the entire installation.

So while it can be tempting to regard the battery as a simple commodity item, to be purchased at the lowest initial cost, I urge the C-suite to look at the bigger picture. A cheap battery can in fact prove very expensive if it fails to function when required, causing loss of subscriber revenues. In contrast, an initially more expensive specialised telecoms battery that delivers in terms of reliability, performance and life will provide a superior return on investment (RoI) as well as peace of mind.

TowerXchange: What are the critical considerations in selecting battery backup power solutions?

There are a number of critical considerations that determine the correct choice of battery for a telecoms installation:

• The duration of backup time required, i.e. the capacity needed to support the duty profile, which largely determines the battery sizing.

• The specific application, will the battery be subjected to frequent daily cycling with deep discharges or will it mainly be on floating duty?

• The environmental temperature, as extremely cold conditions can adversely affect performance, while elevated temperatures reduce the expected life. In some cases, batteries might need to be housed in a specially heated or cooled enclosure.

• The energy density (in terms of both volume and weight), can the battery provide the required performance from the limited installation footprint available at telecom sites?

• Maintenance requirements - how often will the battery need servicing or replacement? At remote locations, the cost of frequent service  visits can exceed the battery purchase cost.

TowerXchange: How does the TCO of Saft’s solutions compare to alternatives?

Currently, the majority of telecom backup power systems are supported by lead-acid (LA) batteries.  While these batteries have operated successfully in the field for many decades, they have some drawbacks, including concerns regarding reduced life expectancy at higher temperatures, shorter cycling life, the necessity to over-size the capacity, low reliability, high weight and low energy density.

In recent years, lithium-ion (Li-ion) battery technology has demonstrated its exceptional capability to deliver high performance, reliability and long life in a range of demanding backup applications. Saft has now created a second generation of Li-ion batteries, known as Evolion® that capitalises on this experience by offering tailor made outside plant hardened modules to meet the specific demands of the telecom industry, where they offer possibilities to create compact, safe and reliable backup power systems.

Thanks to its zero maintenance, sealed for life design, and long calendar and cycle life, Evolion® offers an optimised TCO (Total Cost of Ownership). So while a lead-acid battery might last only up to five years, Evolion^® is designed to have the same life expectancy as the telecom equipment it serves. This means a long float life of 20 years at +20°C and more than 10 years at +40°C and a high cycle life of 4,300 cycles at 80% DOD (depth of discharge) and 8,200 cycles at 50% DOD. Furthermore, unlike lead-acid batteries that are prone to ‘sudden-death’ failures, the life and performance of a Li-ion battery is always predictable. TowerXchange: What are the operational advantages of Saft Li-ion batteries?

The operational advantages of the Evolion^® modules include:

• High energy density (in terms of both volume and weight), delivering high performance from the limited installation footprint available at telecom sites

• High performance in cycling and floating applications

• Safe, reliable operation at extreme temperatures (-40°C to +75°C) that eliminates the need for on site heating or air conditioning

• Easy battery management, since the state of charge (SOC) of a Li-ion battery is directly related to its cell voltage. This also offers the potential for intelligent remote supervision

The main advantage of Li-ion technology for telecom networks is that it enables more energy per weight and volume to be stored. For example, a typical VRLA (valve regulated lead-acid) telecom battery will store 80-95 Wh/l and 35 Wh/kg. In comparison, the Evolion® module stores over 170 Wh/l and 139 Wh/kg, making it effectively two times smaller and four times lighter.

TowerXchange: What are the typical applications in which your batteries are used?

Currently, Evolion^® has four main applications: Outdoor in wire-line/wireless applications with a high quality grid -  including outdoor cabinet applications such as BTS (Base Transceiver Stations), BSC (Base Station Controllers), MSC (Mobile Switching Centres) and access node terminals for FTTx.

At these sites, the battery has to support around 10 to 30 power outages per year ranging from a few seconds to hundreds of minutes.  Since it is in an uncontrolled environment, the battery has to survive temperature ranges from -20°C to +55°C and large variations in relative humidity - Evolion^® can work across this temperature range without affecting performance and life.These sites can be remote and hard to access. In this case, reducing expenses associated with transportation, installation and maintenance is a key objective when considering new solutions. Evolion^® is ‘maintenance free’, with state of health and state of charge information available through remote monitoring. On average, the power required in such applications is in a range of 800 W up to a few kW and the runtimes range from 2 to 8 hours.

CO, MSC and DPCO applications - covering all types of indoor sites with high power requirements (from above 10 kW to several hundreds of kW) that are connected to electrical grids with good or poor quality, and including Central Offices (CO), the more recent architecture of Distributed Power Central Offices (DPCO), where the power is locally distributed and decentralised and MSC (Mobile Switching Centers).  The battery is installed inside under a controlled environment, where the average temperature is typically between +15°C to +25°C.

The Li-ion module is an interesting alternative when compared with the conventional VRLA battery primarily because its low weight and low volume can minimise floor loading and the need for building structural enhancements.

Outdoor and inside wireless applications with no reliable electrical grid - typical of countries where the grid is unreliable. In contrast to the two previous applications, the battery can be discharged several times a day and with a variable depth of discharge.

Again, the battery is usually installed in an uncontrolled environment and must survive a temperature range of -20°C to +55°C and large variations in relative humidity. The average power required is between 1 to 4 kW and runtimes range from 4 to 12 hours.

And again the site is often remote and hard to access.  In this case, reducing expenses associated with transportation, installation and maintenance is necessary.  The Evolion^® module offers high cycling capability at different depths of discharge and in particular at high temperature. Standalone, off-grid hybrid applications - As fuel costs continue to rise, operators are now seeking more cost-effective ways of powering their sites.

A particularly attractive solution is to use a hybrid system that integrates a variable speed diesel DC generator (genset) with a deep cycling Li-ion module. This offers an extremely energy efficient alternative to using an AC generator operating 24/7, since the generator simultaneously charges the battery and powers the site load.

When the battery is fully charged the generator shuts down and the battery takes over as the primary source of power. The genset runtime is reduced to typically 4 hours per day, with major savings in fuel consumption - usually up to 74 percent compared with a standard genset. It also reduces CO2 emissions while increasing refuelling and service intervals.

A complete hybrid system of this type can be packaged in a compact and light ‘energy container’ to offer a turnkey solution that is quick and easy to install in remote locations. The addition of PV (photovoltaic) panels and/or wind turbines could allow further reductions in operating costs (OPEX) while also increasing environmental benefits.

For hybrid sites, Evolion^® offers high cycling capability and long life at deep discharge; fast recharging; resistance to high temperatures; high charge efficiency and ultimately low OPEX. TowerXchange: Finally, please sum up how you differentiate Saft from your competitors?

The important difference with Saft is that we don’t focus on simply selling batteries. We aim to design, develop, manufacture and supply cost-effective energy storage solutions that will ensure high performance and reliability throughout the life of the telecom installation. We are able to do this through our vast experience in the industrial standby power business combined with a wide choice of battery chemistries - including nickel-based and Li-ion technologies - provided within dedicated telecom battery designs and supported by the strength of our global organisation.

All this means that we are able to offer a comprehensive approach that takes telecom customers from a blank sheet of paper through creating the ideal specification for their application, designing and manufacturing the battery system, on site installation and commissioning and then ensuring the system always functions at peak performance by providing through-life service support.