1 rechargeable batteries and battery testing for hospitals cadex electronics inc. december 13 th,...
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Rechargeable Batteries and Battery Testing for Hospitals
Cadex Electronics Inc.www.cadex.com
www.batteryuniversity.com
December 13th, 2005
Bruce Adamse-mail: [email protected]
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OverviewIntroduction – Cadex ElectronicsCommon Rechargeable Battery Types - Which chemistries are most common?
Global demand data, Freedonia
- Advantages and limitations of the common chemistries: Nickel Cadmium, Nickel Metal Hydride, Sealed Lead Acid and Lithium Ion.
- Why batteries fail.
Guidelines for Battery MaintenanceSelecting the Right Battery Analyzer/TesterSummary – - Battery Testing. What to Expect
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Cadex Electronics Inc. – Overview Cadex designs and manufactures battery
chargers and battery analyzers/testers for professionals.
Established in 1980. 25 years of manufacturing and design excellence.
Cadex products are sold in over 100 countries worldwide.
Cadex products and practices comply to CSA/UL/CE/FDA standards for safety, and ISO 9001/13485 and GMP for quality.
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Common Rechargeable
Battery Types – by Global Demand
Demand for secondary batteries
0
1000
2000
3000
4000
5000
6000
7000
1995 2000 2005 2010 2015 by Freedonia
US
$ in
mill
ion
Lead-acid
Li-ion
NiCd
NiMH
Others
Lead-acid batteries account for approximately ½ the worlds’ total demand for rechargeable batteries. Mostly for automotive, and power back-up applications (UPS) including medical equipment.
Lithium ion batteries shows the fastest growing demand.
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Common Battery Types - Advantages & limitationsNickel Cadmium
Advantages – Fast and simple charge.– High number of charge/discharge cycles — if properly
maintained, the NiCd provides 1000+ charge/discharge cycles. – Forgiving if abused — the NiCd is one of the most rugged
rechargeable chemistries.– Best chance of recovery following prolonged storage.
Limitations– Relatively low energy density.– Memory effect — the NiCd must periodically be exercised to
prevent memory.– Has relatively high self-discharge — needs recharging after
storage.
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Nickel Metal Hydride
Advantages – 30%+ higher capacity compared to standard NiCd. – Less prone to memory than NiCd — fewer exercise cycles are
required. Limitations– More complex charge algorithm needed — the NiMH generates
more heat during charge and requires a longer charge time than the NiCd.
– High self-discharge — typically 50% higher than NiCd. New chemical additives improve self-discharge but at the expense of lower energy density.
– Performance degrades if stored at elevated temperatures.
Common Battery Types - Advantages & limitations
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Sealed Lead AcidAdvantages – Inexpensive – lowest cost/watt hour of all common batteries.– Low self-discharge.– Low Maintenance — no periodic discharge is needed.
Limitations– Low energy density - poor weight-to-energy ratio. Mostly used
mostly in power back-up (UPS) or in wheeled applications.– Can not be stored discharged – cell voltage must be maintained
above 2.10V/cell.– Lowest number of full discharge cycles compared to other battery
types.
Common Battery Types - Advantages & limitations
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Lithium IonAdvantages – High energy density — potential for yet higher capacities.– Relatively low self-discharge — self-discharge is less than half that of
NiCd and NiMH. – Low Maintenance — no periodic discharge is needed; no chemical
memory. Limitations– Requires protection circuit to maintain voltage and current within safe
limits.– Subject to aging, even if not in use — storing the battery in a cool
place and at 40% state-of-charge reduces the aging effect .– Expensive to manufacture — about 40% higher in cost than NiCd. – Fuel gauge recalibration required periodically.
Common Battery Types - Advantages & limitations
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NiCd NiMH Li-ion Lead-acid
Gravimetric Energy Density (Wh/kg) 45-80 60-120 110-160 30-50
Internal Resistance in m (includes peripheral circuits)
100-2006V pack
200-3006V pack
<100-2507.2V pack
Less than 10012V pack
Cycle Life (to 80% of initial capacity) 1500 300-500 300-500 200-300
Service Life 5 years + 3-4 years 2-3 years 5 years +
Fast Charge Time 1-2h 2-4h ½-4h 8-16h
Self-discharge / month (room temp.) 20% 30% 5-10% 5%
Cell Voltage (nominal) 1.2V 1.2V 3.7V 2V
Load Current peak best result
20C1C
5C0.5C or lower
2-5C1C or lower
5C
0.2C
Operating Temp. (discharge only) -40 to 60C -20 to 60C -20 to 60C -20 to 60C
Maintenance Requirement 30-60 days 60-90 days 6 months 6 months
Typical Battery Cost (US$, ref. only) $50 (7.2V) $60 (7.2V) $100 (7.2V) $25 (6V)
Cost per Cycle (US$) $0.04 $0.12 $0.14 $0.10
Commercial use since 1950 1990 1991 1970
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Common Battery Types - Why Rechargeables FailEvery battery has a finite life. Choose hardware (charger) and a field service program (Battery Maintenance) that maximizes the number of charge/discharge cycles from your batteries.Poor charging or storage… “ Heat ”Choose a battery and charger to compliment usage patterns and ambient conditions. NiCd charges cooler than NiMH – if you work in a hot climate NiCd is a better choice, if you charger supports both.
Nickel Cadmium and Nickel Metal Hydride batteries develop “Memory” Choose a conditioning charger and professional battery maintenance product.
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The Battery Problem - So What Can You Do?
Weak batteries are picked more often than good ones because weak batteries are charged more frequently and remain on “Ready / Green Light On” longer.
In an emergency situation, the only batteries that are on “Ready / Green Light On” could be the duds.
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Guidelines for Battery Maintenance 1. Isolate Date Expired Batteries
Before use the service date on the battery label is checked and if expired, the battery is isolated so it can be serviced.
Ward A St. Joe’s HsptExpire Date Today85% Batt ID# 1234
Date Expired
TO BESERVICED
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Guidelines for Battery Maintenance 2. Test/Service Battery
TO BESERVICED
Printer
Battery Analyzer
Batteries are serviced on a battery analyzer/tester to restore lost capacity or recalibrate the fuel gauge. Batteries that do not reach target capacity are properly discarded. All batteries with acceptable capacity (80%, or facility defined target) are relabeled.
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Guidelines for Battery Maintenance 3. Relabel Battery and Return to Service
After service batteries are returned to service. All batteries now meet expected performance standards (no weak batteries)
Ward A St. Joe’s Hspt.Expire Date 3 Months Later84% Batt ID# 1234 New Label
SERVICEDBATTERIES
NEW BATTERIES
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Selecting the Right Battery Analyzer/Tester Choose a tester that matches the number
and type of batteries in your facility;- How many batteries can be tested at
the same time?- Are all chemistries supported?- Are all pack voltages (1.2V-30V+)
supported?- Does it perform the right tests (Service
tests along with priming programs for new batteries)?
- Warranty period and upgradeability?- Easy to connect the battery?- How much time will it take?
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Choose a tester that allows you to collect service data and record/report the results appropriately. PC software and accessory label printer may be required.
Choose a tester that can be updated to support batteries for future medical devices. Interchangeable adapters make it easy to accommodate new battery types.
Selecting the Right Battery Analyzer/Tester
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Summary – Battery Testing What to Expect
Test Time/Battery. 6-10 hrs. for NiCd, NiMH. 12-15 hrs. for Li-Ion. 24 hrs. for SLA.Recommended Service Period/Battery Type. NiCd – every 30-60 days. NiMH –every 60-90 days. SLA and Li-Ion every ~6 months.Amount of Operational Time Required – Once installed, less than 30 minutes per day.The bottom-line line: Battery testing will improve reliability of medical equipment and minimize the expense of unnecessary battery replacement (lower cost of operation).
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Thank [email protected]
For more on battery-related products and information visit the following websites:
www.cadex.com Corporate website
www.BatteryUniversity.com Educational website; offers practical information for battery users in essay
form.
www.buchmann.caInformational website; carries articles and the book: "Batteries in a Portable
World — A handbook on rechargeable batteries for non-engineers”