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Editorial Topic by Meir Portnoy: Are Lithium Ion Batteries on the Way to Replace Lead
ACID batteries in UPS Systems ?
"More and more cases are published, where Lithium Ion batteries are preferred over lead acid
batteries based on longer lifetime, increased backup time and environment friendliness."
This statement, introduced by us in the Industry News section of our last monthly newsletter is
supported by market studies and new product introduction; such as July 2011 Lux market study,
briefed on UPS News in July 2011, which expects Li-ion batteries to grow 23% per annum from
USD 795 million in 2011 to USD 2.2 billion in 2016, reaching in 2016, 6.8% of UPS capacity and
5.8 % telecom backup capacity, and new Toshiba UPS, equipped with 10 years Lithium Ion
batteries, which was also introduced in July 2011.
Lithium Ion batteries, although widely used in portable electronics, are slow in penetrating the UPS
and backup power system market, mainly because of safety concerns and cost. This attitude is
however changing, due to introduction of new Li-Ion batteries with protection circuits, and
because of their inherent green features. We have therefore found of value to dedicate this
Newsletter, to the aspects of using Lithium Ion batteries for UPS backup.
We think that the best way to consider the Pro's and Cons of using Li Ion batteries in UPS
environment, is to examine an implementation of a practical solution. We have therefore decided
to compare popular Li Ion battery characteristics, with the most popular 7AH Valve Regulated
Lead Acid (VRLA) battery, in a string, comprising 40 such VRLA batteries connected in series, in
order to backup about 10kW three phase transformer-less UPS. For higher powers, additional
strings can be added in parallel, or cells with higher capacities can be selected.
For this purpose, VRLA Yuasa Battery Europe Gmbh, 12 Volt 7AH type NP 7-12 was selected, to
be compared with Gaia Lithium Ion battery cells type UHP341440NCA ( 7AH , 10 Hour rating)
from Lithium Technology Corporation USA. The Gaia battery is commercially available as a single
3.6V cell; for comparison purpose additional 30% packing allowance was added to UPS battery
weight and volume. Gaia battery was selected based on its popularity and detailed technical
information provided by the manufacturer. Although some battery manufacturers offer LI Ion
batteries having the size and voltage that replace NP 7-12 VRLA batteries, not enough information
was found for meaningful comparison.
Technical Data and Performance Comparison
Readers are invited to see the comparison, by linking to our page titles: VRLA versus Li Ion v UPS
Battery . The presentation emphasizes the following main highlights:
1. Both batteries provide 7Amperes for 10 hours. VRLA battery bank, made of 40 series
connected 12 V batteries totaling 240 cells, 2volt each, has equivalent voltage and capacity as a Li
Ion bank comprising series connected 133 cells, 3.6 V each.
2. The Volume and Weight of Li Ion battery bank (including 30% packing allowance) is almost
50% smaller and 50% lighter.
3. Maximum allowed discharge current of LI Ion battery is 400% higher, compared to VRLA
4. The Li Ion Battery provides considerably longer backup times at high discharge currents.
Whereas 7AH VRLA battery provides barely 5 minutes backup at 3C rate (21 Ampere) discharge
current, the Li Ion battery offers 18 minutes backup with the same discharge current.
VRLA Backup time of 15 minutes is almost twofold longer when Li Ion battery is used.
5.The Li Ion battery offers 6 times more 100% Depth of Discharge (DOD) cycles; and up to 25
times more 30% DOD discharges compared to VRLA battery.
6.The Life expectancy of Li Ion battery at any temperature is at least two times longer than VRLA
7. Self discharge time of Li Ion battery at 20 degrees C is 40% shorter it should be recharged
every 3 to 5 month in storage, compared to 8 to 10 months storage before recharging a VRLA
8. VRLA and Li Ion batteries share almost the same operating temperature range, and temperature
has similar effect on battery capacity.
It is evident that Li Ion batteries provide better performance, on most aspects of
Firstly, Reliability of Li Ion battery bank is considerably higher compared to VRLA batteries, due
to longer life span, considerably more discharge cycles, and almost 50% less cells in a battery
Secondly, smaller Li Ion battery volume enables smaller foot print; whereas smaller weight enables
easy handling contributing to lower Mean Time to Repair (MTTR), both of prime importance in
certain applications such as Data Centers.
Thirdly, the batteries allow longer backup time in less space, decreasing the need and dependence
on backup generators.
Fourthly, high maximum discharge currents enable simple isolation of failed battery string in
parallel strings configuration, increasing also UPS overload capabilities, without Static Switch
In addition, Lithium Ion batteries have no gas emission, may operate in totally sealed environment,
and can be disposed according to normal solid waste disposal regulations.
Hazardous Nature of Li Ion Batteries
Lithium Ion cells are made from a Carbon Anode, a Metal Oxide Cathode, and lithium salt
electrolyte in organic non-aqueous solvent. Lithium is a very active material, therefore the
electrolyte includes flammable constitutes, which may burn when high temperatures are elevated,
due to overcharges, or over currents.
Lithium-ion batteries are therefore considered to be Class 9 Hazardous Materials, which cannot be
transported by air, and should be shipped by ground carrier as Lithium Batteries under United
Nations relevant classification.
In order to eliminate possibility of flammable hazards, most Li Ion manufacturers' offer today also
charging and monitoring circuits that can be installed inside the battery package, which control
battery charging as required by the manufacturer, and protect the battery from hazardous
phenomena. These circuits protect the battery against such incidents as reverse polarity, high
charging temperature, high charging current, short circuit, over-voltage, over discharge, and high
Lithium Technology for instance, offers a battery management system ( BMS), built on Printed
circuit board that can be included in system battery package, which takes care of battery energy
and thermal management. Certain IC manufacturers such as Texas instruments offer Lithium Ion
battery monitors and protection circuits able to protect series cells in a battery string.
Cost of Lithium Ion versus VRLA battery.
High Cost of Li-Ion batteries seems to be another obstacle limiting the use of these batteries for
UPS backup. The price of LI-Ion batteries is generally five to eight times higher, compared to
same Ampere Hour sized VRLA Batteries. A USA company, Batteryspace.com for instance, offers
12 Volt 7AH VRLA battery for US $ 16.00 , and Li-Ion battery replacement, having exactly the
same AH and physical size and internal Printed Circuit Protection Board , which takes care of
Overcharge, Over Discharge and Over Drain, for US $ 95, which is almost 6 times higher.
But, most internal batteries in medium power UPS systems are rated for 5 minutes. Thus, a
7AH Li Ion battery, which offers 18 minutes backup instead of 5 minutes provided by a VRLA
battery, and has three times longer life expectancy, should be valued almost 12 times, not six
times higher. Taking in account also additional factors affecting longevity, and costs such as
discharge cycles, maintenance cost, lease of footprint space, would probably make it cost
effective even when the multiplier is 20.
Looking at it from a different angle, we can meet the 20Amp 5 minute backup time using a
smaller sized Li Ion battery. Li Ion battery rated 4AH discharged at 5 times its capacity (5C) as
allowed, is sold by Batteryspace.com for US $ 40, decreasing the cost multiplier to less than 4.
Although, the ratio of Li Ion and VRLA backup time, decreases with increased autonomy time,
still the marked advantages of Li Ion battery make it more cost attractive.
The future of Lithium Ion Batteries
Based on the results of the simple Li-Ion v VRLA comparison on UPSonNet website, it seems
evident that Li Ion technology wins almost on any aspect, and should be preferred provided that
necessary precautions to avoid hazardous situation are in place. Thus, the said Lux forecast,
anticipating Li Ion to grow 23% per annum and get 6.8% of UPS backup capacity by 2016,
doesn't seem exaggerated.
Not the technically based logic however, but our fears to make a change seem to be the main
obstacle to vote for Li Ion, while abandoning the Lead Acid technology in spite of its numerous
Here, we need probably an outsider to make the decision.
Andrew Grove, the legendary Intel's co founder and CEO, describes in his book "Only the
Paranoids Survive" what made Intel to transform from a memory chip producer to world's
dominant microprocessor manufacturer. Until 1976, memory chips were Intel's main product; by
that time Intel confronted decreasing demand and falling income, due to Japanese competition and
dumping of memory chips at below cost prices. Grove's decision to go out of the memory chip
market and make a radical change followed his question: "What would an outsider manager do?"
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Remark: UPSonNet is a consulting and information source; all Information and opinions in our
articles, newsletters and guides is based on unbiased judgment of our editor and writers. This
doesn't refer to Information presented on directories,advertisements, news,company profiles and
other material, which is provided or published by the relevant industry members.
UPSonNet Website News
We have brought to the attention of our Newsletter subscribers two months ago, that we enable
visitors that missed monthly newsletters, to close the gap by presenting on UPSonNet website
the previous Newsletter, before a new monthly newsletter is circulated to subscribers.
Whoever missed our latest Newsletter dealing with possible malfunction of UPS systems operating
with leading Power Factor loads, is invited to read the editorial titled: UPS operation with Blade
Servers and other Leading Power Factor Loads.
UPS Industry News
Two market studies, briefs of which are presented in July 2011 on UPSonNet News, indicate a
positive outlook and promising future for UPS and Power Backup field in emerging markets for
the next five years.
Flux research, expects Off Grid Storage market to grow by 36% until 2016, mainly in such
sectors as: Flywheels, Lithium Ion batteries, Fuel cells and Ultra Capacitors.
Pike Research report, forecasts that Commercial Buildings' UPS Market is expected to grow by
41% up to $4.8 Billion until 2016.
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|Spread Your Word On the Globe
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