Batteries for UPS: Main Technologies, Advantages, and Disadvantages

1. SIRET Clemence;ChristophJehle (c.jehle@web.de);Jean-PolWiaux;PhilDolley;mailto:Claude.CHANSON@saftbatteries.com;StephanieBoulos;Bob Harrison (robert.harrison@which.net);bob.harrison@intertek.com;ecoups; CONFIDENTIAL SAFT Feb 6 2012 C. Chanson

2. Batteries for UPS: main technologies Advantages and disadvantages in UPS application

3. Batteries for UPS applications: type of batteries • The main chemistries used in UPS applications are the following • Lead acid batteries (Pbacid) • Nickel metal hydride batteries ( Ni-MH ) • Nickel cadmium batteries( Ni-Cd) • Lithium ion batteries ( Li-ion and Polymer Li-ion) • According the manufacturer and the battery usage, different products are proposed: • Technology specifics : Pb acid VRLA or flooded, Ni-Cd pocket plates or sintered, Li-ion NCA cathode, NMC cathode, free electrolyte or polymer, etc… • Application specifics: power batteries for high rate discharge ( less than 1 hour), energy batteries for low rate discharge. 2

4. Batteries for UPS applications: marketsshares • Lead acid market share for UPS application is around 95%. • Ni-Cd and Ni-MH cells have a few percent market share for industrial UPS • Volumes in 2011 in Europe represents around 500 MWh/y (TBC) • Li-ion are being proposed both for “consumer” and “industrial” UPS. The market share is still small, but growing. 3

5. Batteries for UPS applications: performances • For UPS application, some specific technical properties may be considered as more relevant: • Power and energy  according UPS specification • Energy density  size and weight of the equipment • Energy efficiency  battery recharge time and cost • Maintenance charge energy saving • Maintenance operations  service organization and cost • Life duration  total life cycle cost, and replacement scheme 4

6. Power, Energy, Energydensity • For each chemistry, full range of energy and power batteries are available to fit different UPS specifications. • Volumetric energy density at cell level: range of characteristics according the battery type. • The UPS energy density depends in addition on the system design.The battery pack, rack, shelves, or cabinets layouts are not considered in this graph. (Source: J.M. Tarascon, Amiens University, France, and handbook of batteries McGrawhilled.) 5

7. Energyefficiency -1 • The energy efficiency is the ratio of the discharged energy vs the charged energy. It corresponds to the product of the voltage efficiency by the coulomb efficiency. It of course depends on many factors, and mainly on: • Battery chemistry and technology • Temperature • Currents for charge and discharge • Battery ageing • A comparison can proposed based on new batteries designed for UPS or similar application, at room temperature and low currents (1). (1) Energy analysis of batteries in photovoltaic systems. Part I:Performance and energyrequirements Carl Johan Rydh, BjôrnA. Sande, Energy Conversion and Management 46 (2005) 1957–1979 6

8. Energyefficiency -2 • Characteristics of technologies applicable to UPS usage: • Lead acid coulomb efficiency considered at 82% (2) , approximate voltage efficiency: (2V)/(2.26V) = 88%, leading to energy efficiency = (87%)(90%) = 72% (3) • Ni- Cd and Ni-MH have a similar behavior: coulomb eff. 85% and voltage efficiency: (1,23V)/(1,38V) = 89%, energy eff. = 76% (4) • Li-ion have a coulomb efficiency close to 100% ( no side reaction when charged up to 100%), and voltage efficiency (3,6V)/(3,75V) =96%, leading to an energy efficiency = 96% (5) (2) A Study of Lead-Acid Battery Efficiency Near Top-of-Charge and the Impact on PV System Design John W. Stevens and Garth P. Corey, S.N.L,USA(photovoltaics.sandia.gov/docs/.../batpapsteve.pdf ) (3) Lead acid battery lecture (ECEN 4517/5517)(ecee.colorado.edu/~ecen4517/materials/Battery.pdf) (4) Saft Ni-Cd technical leaflets: SPH range, Uptimax range (www.saftbatteries.com) (5) Saft Li-ion technical leaflet: Evolion system(www.saftbatteries.com) 7

9. Maintenance charge • Why a maintenance charge: • In order to maintain the battery capacity at his maximum and compensate self discharge, a maintenance charge is generally required by the battery supplier. • The maintenance charge correspond to the battery manufacturer specification, and can be applied in several ways: continuous current or pulses, current or voltage controlled, etc.. • In general, this maintenance charge represents a fraction of the energy consumption of the global battery system including electronics. • Typical values of currents for Pb-acid, Ni-Cd and Ni-MH are in the range of C/5000 to C/500 rate( ie 20 to 200 mA for a 100 Ah battery). So the total consumption of energy per year will be 2 to 20 times the battery energy (6) (7) (4) • For Li-ion, due to the better charge efficiency, the total energy consumption will be 0,1 to 0,5 time the battery energy, to compensate self discharge (5) (6)R.F. Nelson, »Valve-Regulated Lead-Acid Batteries », p 258,  publishedby Patrick T. Moseley,JurgenGarche,C.D. Parker,D.A.J. Rand (http://books.google.fr/books?id=5R...) (7) Enersysleaflet “powersafe” US-FL-IOM-002 January 2007(www.enersysreservepower.com/.../US-FL-IOM-0..) 8

10. Maintenance operations and life duration • Maintenance operations may be requested, particularly in case of non-sealed batteries: according the battery manufacturer specification, filling and other maintenance operation may be requested on the battery or the system. • Life duration of a battery may depend on the usage conditions, temperature, charge systems, etc.. • The values announced by the manufacturers are in the following ranges for ambient temperature up to 30°C: • - up to 10 years for lead acid • - up to 20 years for Ni-Cd, Ni-MH and Li-ion 9

11. Integration and recyclability • Different type of systems can be proposed according the size of the system: • Small systems (typically lower than 10 kWh): in general, small system are more integrated for more “standard type” operations: few maintenance possibilities, standard interchangeability. In this case, battery manufacturers consider application of the battery directive: system design should integrates the possibility to remove and recycle the battery or battery cells. • Large systems: these are more oriented towards specific installation and maintenance, with a lower cost replacement unit: this leads in general to a lower integration of electronics and electrochemical cells. In this case, there should be no specific difficulties dismantle and handle batteries modules or battery cells for recycling. 10