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south-east european

INDUSTRIAL MARKET 3

PAID ARTICLE

SPC (Super Pulse Cell Capacitor) and ES

energy storage systems from EVE Energy in

the Endrich line up

Electronics devices, which are designed for short term

operation and stay long in stand-by mode need huge

energy impulse immediately after wake-up. Emergency

alarm systems, RFID transponders, GPS tracking devic-

es, smart meters' read-out electronics or the recently

obliged E-CALL systems of passenger vehicles need a

battery with stabile voltage, low leakage, being able to

pump huge momentary charge into the system. These

requirements are often realized by integrating super-ca-

pacitors, that have ten or even hundred times higher en-

ergy density than normal electrolytic capacitors, their

charge and discharge times are also shorter, and toler-

ate much more cycles that e.g. rechargeable batteries.

Supercap's operation is mainly based on electrostatic

charge, however there are some special devices, like

EVE Energy's own patented SPC devices featuring

chemical working principle. They are mainly in use as a

part of a special battery pack. This paper introduces the

advantages of such system.

SPC device

The super pulse capacitors produced by EVE are mo-

mentary high-current discharge devices that can oper-

ate in the operational temperature range of -40°C to

+85°C. SPC's unique chemical lithium structure is based

on EVE's own patents. The hermetically closed and

sealed enclosure with safety valves makes the design

superior safe even in applications where traditional su-

per-capacitors cannot be used. One of this areas is the

gas metering, where SPC with its ATEX approval is an

ideal solution for energizing smart-meter's readout, as

the safety valves make the device explosion proof.

The cell voltage is 3.6V, and no passivation appears,

which other lithium battery families are suffering from.

The self discharge remains under 2%, which makes it

possible to stay long in stand-by more and activate fast

to pump momentary large charge into the circuit.

If a smart meter contains a standalone ER (lithium thio-

nyl chloride) battery, the voltage delay caused by the pas-

sivation effect may cause problem in operation. Passiva-

tion is a phenomenon of lithium primary cells related to

the interaction of the lithium metal anode and the electro-

lyte. A thin so called passivation layer forms on the sur-

face of the anode at the moment the electrolyte is injected

into the cell during production. This layer is important be-

cause it protects the anode from reaction while the cell is

not affected by load, resulting in a long shelf-life. Under

load, when battery starts to discharge, the current flowing

through the cell will start to rebuilt this layer. Under normal

conditions, the thin passivation layer does not affect or

degrade the performance of the battery cell. When the

layer grows too thick due to long storage, discharge per-

Dipl.Ing. Zoltan Kiss Sales manager East Europe

Endrich Bauelemente Vertriebs GmbH

Zoltan Kiss Sales manager - Eastern-Europe; e-mail: z.kiss@endrich.com

formance may be affected. The development of the passi-

vation layer is influenced by the conditions of the storage,

long unloaded periods of months or years and keeping

the cells above room temperature (23-25°C) will cause

the passivation layer to grow thicker. A passivated cell

may show voltage delay when suddenly applied under

load, the voltage response is delayed. In such cases a

smart utility meter - being in stand by for a long period of

time - will not operate perfectly, the readout electronics

may not start and the data transfer may fail. A possible

solution for such cases to use an SPC device in addition

to the ER battery.

Combined solution: EVE ES energy storage systems

EVE's SPC is a standalone device, however on the

field it is often used in combination with ER cells, which

are responsible for providing enough capacity. By con-

necting the two cells in parallel, the lithium metal primary

battery will keep the SPC fully charged. EVE's ES bat-

tery packs are formed by an SPC and a lithium thionyl-

chloride (Li-SoCl

2

) battery as seen on the figures:

Of curse there are different combinations by means of

number of ER cells behind the SPC, or using even more

SPC devices in the same time:

Lithium thionyl chloride cells have a metallic lithium

carbon - the lightest of all the metals - anode and a liquid

cathode comprising a porous current collector filled with

thionyl chloride (SoCl

2

). They deliver a nominal voltage

of 3.6V, their open circuit voltage is 3,66V and during

load with their 3.4-3,6V closed circuit voltage they are

one of market's highest voltage primer cells. Lithium

thionly chloride batteries are the primary battery current-

ly with the highest voltage and energy density (1280 Wh/

dm

3

), longest storage (10-20 years) , and the least self-

discharge rate of 1%@20°C. The battery is capable of

operation in a wide temperature range normally from -

60°C~+85°C. Those batteries are ideal for such long-

term applications as power for electric devices and elec-

tric power, water, heat and gas meters, and especially

as backup power source for memory ICS. There are larg-

er pulse current spiral types as well as higher capacity

bobbin cells in the program. The bobbin type is safer,

however usually it has a voltage delay and its pulse ca-

pability may be not enough to supply momentary large

current to the device (passivation).

Marrying the SPC and the bobbin type ER technolo-

gies, we can combine the advantages. Lithium primer

battery will store enough capacity and keeping SPC fully

charged all the time, while SPC device is able to pump

pulse charge fast to the system. Other manufacturers

combine ER batteries with super capacitors, in compari-

son of the two technologies, the lithium chemistry based

SPC systems offer the following advantages:

· Higher cell voltage ( 3,6V vs. max 2,7V)

· Much smaller impedance ( <150 m

vs. 400 m

)

· Higher capacity( >270F vs. max 100F)

· Much higher energy density

· By orders of magnitude less leakage current, which

is even almost independent from temperature, sav-

ing ER battery life (<1

µ

A)

· Much wider operating temperature range

· Much longer service life (~15 years)

· Much safer battery pack( UL1642 UN 38.3)

The figure shows, that fast charge pumping of the SPC

covers the voltage delay caused by passivation of Li/

SoCl

2

cell, and the pack voltage never goes below the

working voltage of the device. The measurement has

been done by using 10 mA continuous load current with

a pack formed by an ER14250 battery and an SPC1520

energy storage system.

Other measurement show that the leakage current of

the EVE ES system at -30°C stays under 2

µ

A, at +25°C

stays under 1

µ

A while at +85°C it will be still below 5

µ

A,

therefore considered to be stabile independent from am-

bient temperature. Lifetime expectation can reach 10-15

years, the pack is able to provide as high as 1A of pulse

current, due to its safe construction it can be used in

sensitive environment (ATEX). The combined pro-duct

successfully provides solution for both high energy den-

sity (large capacity) and high power density (high mo-

mentary current) requirements.