Transcript Li-ion - sparc

The Care and Feeding of Batteries
Ham Perspective
February 13, 2003
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OUTLINE
 History
 Battery
Types
 Characteristics
– Internal Resistance
– Discharge
– Charge
Pulse Charging
 Termination Methods

 Service
Life
 Precautions
 Trends
 Conclusion
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History
Time
1791
1792
1802
1813
1820
1827
1833
1836
1839
1859
1868
1874
1878
1880
1881
1885
1887
Event
Frog leg experiment
Voltaic piles
Mass produced battery
Giant battery (2,000 cells)
Electricity from magnetism
Ohm's law
Ionic mobility in Ag2S
Cu/CuSO4, ZnSO4/Zn
Principle of the air cell
Lead acid battery
Zn/NH4Cl/C wet battery
Telegraph
Air Cell
High capacity lead/acid
Zn/NH4Cl/C encapsulated
Zinc-bromine
Zn/NH4Cl/C dry battery
Name
Galvani
Volta
Cruickshank
Davy
Ampere
Ohm
Faraday
Daniell
Grove
Planté
Leclanché
Edison
Maiche
Faure
Thiebault
Bradley
Gassner
Time
1891
1899
1900
1905
1911
1927
1930
1943
1945
1950
1956
1959
1983
1991
1992
1995+
Event
Thermodynamics of dry cells
Nickel cadmium battery
Ni Storage batteries
Ni iron batteries
Automobile self-starter
Silver zinc
Nickel-zinc battery
Cuprous chloride battery
Mercury cell
Sealed mercury Cell
Alkaline fuel cell
Alkaline primary cell
Lithium metal rechargeable
Commercial lithium ion
Reusable alkaline
Recent developments
Name
Nernst
Nernst
Edison
Edison
Kettering
Andre
Drumm
Adams
Ruben
Ruben
Bacon
Urry
Moli
Sony
Kordesch
..
If you would not be forgotten as soon as you are dead
& rotten, either write things worth reading, or do
things worth the writing."
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Benjamin Franklin
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General Types
 Secondary
Cells
 Zinc Air
 Lithium
 Lithium
 Alkaline
 Nickel
 Carbon
Metal Hydride
 Nickel Cadmium
 Gel Cell
 Lead Acid
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 Primary
Cells
Zinc
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Evolution of Cell Technologies
Rechargeable cell technology has made dramatic strides in the past twenty years, offering new
product design options while increasing energy density
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Energy Density Comparison
Pb
Lithium-ion/polymer cells offer higher energy density versus Ni-MH and NiCd. Lithium-polymer is typically a thinner cell than the equivalent capacity
lithium-ion, which may be a key consideration.
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Internal Resistance




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Internal Resistance is an important characteristic for applications that
require periods of high current
Handhelds or any receive/transmit situation are examples of
intermittent high drain applications.
This characteristic is the factor that favors the use of NiCad or NiMH
AA cells over alkaline cells even though the alkaline cells have a
higher rated capacity.
General preference
– NiCad, SLA, Li-Ion, NiMH, and Alkaline

Internal resistance increases as cell discharges

– More so for SLA and Alkaline
Specific Application is the determinant
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Discharge Comparison
Alkaline
The device operational
voltage limits are
important factors in
battery charge
utilization
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NIMH
0.8 Volt is considered full
discharge
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Characteristic
Gravimetric Energy Density
(Wh/kg)
Internal Resistance
(includes peripheral circuits) in
mohms
Cycle Life (to 80% of initial
capacity)
Fast Charge Time
Overcharge Tolerance
Self-discharge / Month (room
temperature)
Cell Voltage (nominal)
Load Current
- peak
- best result
Operating Temperature
(discharge only)
Maintenance Requirement
Typical Battery Cost
(US$, reference only)
Cost per Cycle (US$)11
Commercial
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NiCd
45-80
100 to 2001
6V pack
15002
1h typical
moderate
NiMH
60-120
200 to 3001
6V pack
300 to 5002,3
2-4h
low
20%4
30%4
1.25V6
1.25V6
20C
1C
-40 to
60°C
30 to 60 days
$50
(7.2V)
$0.04
1950
5C
0.5C or lower
-20 to
60°C
60 to 90 days
$60
(7.2V)
$0.12
1990
Lead Acid
30-50
<1001
12V pack
200 to
3002
8-16h
high
5%
2V
5C7
0.2C
-20 to
60°C
3 to 6 months9
$25
(6V)
$0.10
1970
Li-ion
110-160
Li-ion
polymer
100-130
150 to 2501
7.2V pack
500 to 10003
10%5
3.6V
>2C
1C or lower
-20 to
60°C
not req.
$100
(7.2V)
$0.14
1991
80 (initial)
200 to 3001
7.2V pack
300 to
500
2-4h
very low
Reusable
Alkaline
200 to 20001
6V pack
503
(to 50%)
2-4h
low
2-3h
moderate
~10%5
3.6V
0.3%
1.5V
>2C
1C or lower
0 to
60°C
0.5C
0.2C or lower
0 to
65°C
not req.
$100
(7.2V)
$0.29
1999
not req.
$5
(9V)
$0.10-0.50
1992
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Technology Comparisons
Pros
Cons
• Long cycle life (500+)
• Excellent low temp capacity (up to
-30ºC)
• Environmental concerns due to
cadmium
• Low energy density and high self
discharge
• High rate capability
• Memory effect
• Medium cycle life (400+)
• Lower charge efficiency
• 30% more energy density than NiCd
• High self discharge
• Environmentally friendly
• Poor rate capability
• Medium
• Lowest shelf life
Ni-Cd
Ni-MH
Li-ion
cycle life (400+)
• Highest energy density
• Complex charge controls required
• Very low self discharge
Li-ion Polymer
• Same
as Li-ion
• Same as Li-ion
• No metal "can"
• Difficult
• Broad and thin design capability
• Lower
• Lack
to handle
charge rate capability
of field history
• Cost
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Application Feature
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Comparison of Nickel-Metal Hydride to Nickel-Cadmium
Batteries
Nominal Voltage
Same (1.25V)
Discharge Capacity
NiMH up to 40% greater than NiCd
Discharge Profile
Equivalent
Discharge Cutoff Voltages
Equivalent
High Rate Discharge Capability
Effectively the same rates
High Temperature (>35oC) Discharge Capability
NiMH slightly better than standard NiCd cells
Charging Process
Generally similar; multiple-step constant current with overcharge
control recommended for fast charging NiMH
Charge Termination Techniques
Generally similar but NiMH transitions are more subtle. Backup
temperature termination recommended.
Operating Temperature Limits
Similar, but with NiMH, cold temperature charge limit is 15oC.
Self-Discharge Rate
NiMH slightly higher than NiCd
Cycle Life
Generally similar, but NiMH is more application dependent.
Mechanical Fit
Equivalent
Mechanical Properties
Equivalent
Selection of Sizes/Shapes/Capacities
NiMH product line more limited
Handling Issues
Similar Memory and Depression?
Environmental Issues
Reduced with NiMH because of elimination of cadmium toxicity
concerns
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Lithium-ion vs.
Lithium-ion Polymer
Pros
Li-ion Technology
•State-of-the-art
•Cell material in rigid metal can
•Mechanically robust construction
•Tolerant to mild pressure build up
Cons
•No manufacturing flexibility
•Loses (20%) energy efficiency with thin cells
Li-ion Polymer Technology
•Next level of improvement
•Soft plastic package
•"Soft" construction
•Maintains energy efficiency with thin
cells
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•Limited manufacturing flexibility
•Cells easily bulge upon pressure build up
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Li –Ion vs. Li Polymer
The Li-ion polymer offers little or no energy gain over conventional
Li-ion systems; neither do the slim profile Li-ion systems meet the cycle
life of the rugged 18560 cell. The cost-to-energy ration increases as the
cell size decreases in thickness. Cost increases in the multiple of three
to four compared to the 18650 cell are common on exotic slim battery
designs.
If space permitted, the 18650 cell offers the most economical choice,
both in terms of energy per weight and longevity. Applications for this
cell are mobile computing and video cameras. Slimming down means
thinner batteries. This, in turn, will make the cost of the portable power
more expensive.
*Note- The 18560 is probably the only Li battery that would be feasible for to attempt to use in a
general purpose (ham) setting. Even then, the charger would need be carefully fit to the
application.
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Alkaline Cells
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Note: An inexpensive source for Alkaline AA’s is
Costco. The Kirkland’s are about $0.25 each
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Primary Alkaline vs. Rechargeable
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NiCad
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NiCad vs. NiMH
NiMH
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Charging Lithium-ion Chemistries
Voltage
When Lithium-ion batteries are charged, the voltage will continue to rise. Therefore, the
charger must manage the battery voltage to define charge termination and optimize battery
life.
Temperature
Lithium-ion batteries are not exothermic until they overcharge.
Charge Control
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•Constant current-constant voltage limit (4.2 V maximum)
•Typical charge time is 2.5 hours with host turned off at 25º C
•Temperature cut off is typically not used (Temperature is fairly constant with this
method.)
•Safety: Overcharge can cause failure.
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Typical 7AH Gel Cell

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Typical Gel Cell
(Power-Sonic 1270)
Measuring the open circuit
voltage of a gel cell can
provide a good indicator of
its state of charge. This is
especially true if you have
the specifications for the
particular battery.
An approximation is –
12.8 - 13 V – Full charge
11.5 - 11.8 V - 10% charge
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NiCd Charge vs. Temp, Pressure
The profiles for NiCD and NiMH are similar but note that it is difficult, if not impossible, to slow-charge a NiMH battery on the basis of these
characteristics. At a C rate of 0.1C and 0.3C, the voltage and temperature profiles fail to exhibit defined characteristics to measure the full charge
state accurately and the charger must rely on a timer. Harmful overcharge can occur if a partially or fully charged battery is charged with a fixed
timer. The same occurs if the battery has aged and can only hold 50 instead of 100 percent charge. Overcharge could occur even though the
NiMH battery feels cool to the touch.
Lower-priced chargers may not apply a fully saturated charge. The full-charge detection may occur immediately after a given voltage peak is
reached or a temperature threshold is detected. These chargers are commonly promoted on the merit of short charge time and moderate price.
Some ultra-fast chargers also fail to deliver full charge.
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Charge Termination Methods
Constant voltage with current termination
•Suitable for Li-ion, Li-ion polymer and Lead Acid
•Terminate based on set current value
•Simple in implementation but requires better accuracy for safety and
performance
Time-based termination
•Suitable for all chemistries (Li-ion with constant voltage charging
•Low cost and simple design
•Applicable for low current and slow chargers only
Temperature termination (not applicable for Li-ion chemistries)
•Delta temperature/delta time: Suitable for nickel chemistries
•85-90% complete charging (100% with trickle charging)
•Absolute temperature cut off (TCO)
Delta voltage termination (not applicable for Li-ion chemistries)
•Suitable for nickel chemistries (best for Ni-Cd)
•Less accurate method
Commercial fast-chargers are often not designed in the best interests of the battery. The two common battery
killers are high temperature during charge and incorrect trickle charge after charge.
Choosing a quality charger makes common sense. This is especially true when considering the high cost of
battery replacements and the frustration poorly performing batteries create. In most cases, the extra money
invested in a more advanced charger is returned in longer lasting and better performing batteries.
The selection of the ‘best’ method, is closely coupled to whether the method is being applied to a cell or
battery (multiple cells in series), what the charge rate will be, and the chemistry involved. Some say that the
‘best’ method is to employ delta temperature, delta voltage or voltage inflection, with time and max temp as
backups. Li is class unto its own.
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Power Sonic Charging (7 AH)
Cycle Applications: Limit initial current to 1500mA. Charge until battery
voltage (under charge) reaches 14.40 to 14.70 volts at 68 F
(20 C). Hold at 14.40 to 14.70 volts until current drops to approximately
70mA. Battery is fully charged under these conditions, and charger
should either be disconnected or switched to “float” voltage.
“Float” or “Stand-By” Service: Hold battery across constant voltage
source of 13.50 to 13.80 volts continuously. When held at this
voltage, the battery will seek its own current level and maintain itself
in a fully charged condition.
NOTE: Due to the self-discharge characteristics of this type of battery, it is imperative
that they be charged after 6-9 months of storage, otherwise permanent loss of
capacity might occur as a result of sulfation.
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Sealed Lead Acid Considerations
Finding the ideal charge voltage limit for a sealed lead acid system is critical. Any
voltage level is a compromise. A high voltage limit produces good battery
performance, but shortens the service life due to grid corrosion on the positive
plate. The corrosion is permanent and cannot be reversed. A low voltage preserves
the electrolyte and allows charging under a wide temperature range, but is subject
to sulfation on the negative plate.
Once the SLA battery has lost capacity due to sulfation regaining its performance is
often difficult and time consuming. Reasonably good results in regaining lost
capacity are achieved by applying a charge on top of a charge. This is done by fully
charging an SLA battery, then removing it for a 24 to 48 hour rest period and
applying a charge again. This is repeated several times, and then the capacity of
the battery is checked with a full discharge. The SLA is able to accept some
overcharge, however, too long an overcharge could harm the battery due to
corrosion and loss of electrolyte.
Applying an over-voltage charge of up to 2.50V/cell for one to two hours can
reverse the effect of sulfation of the plastic SLA. During that time, the battery must
be kept cool and careful observation is necessary. Extreme caution is required not
to raise the cell pressure to venting point. Cell venting causes the membrane on
some SLA to rupture permanently. Not only do the escaping gases deplete the
electrolyte, they are also highly flammable!
There are a number of other approaches advertised that use various pulsing, reflex
charging and ‘resonant frequencies’ to prevent or recover batteries from the effects
of sulfation. The is some evidence that these approaches are effective, at least in
the short term, but the major battery producers have not endorsed or discouraged
the approaches.
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Pulse Charging, Sulphation and Conjecture

Why
– Rapid Charging
– Conditioning
 Discharge Pulse
– Reduce Bubbles
– Reduce Capacitance
– Stir Electrolyte

Equivalent Circuit
SULFATION Removal
What Frequency/duty cycle is best?
Swept, PbSO4 Resonant Frequency?
See the Internet for details but be aware that there
are contrasting opinions about the effectiveness
and long term benefits of some of the sulfation
removal removal approaches.
Wallwarts can be a cheap front end to a
homebrew charger or de-sulfator.
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Contrasting Opinion
Negative Pulse Charge "Burp" Charging - Fact or
Fiction?
– http://www.rcbatteryclinic.com/me
nu.htm

http://www.flex.com/~kalepa/desulf.htm Pulser circuit & info
http://www.uoguelph.ca/~antoon/circ/bcgla.htm Gel cell charger
http://users.pandora.be/vandenberghe.jef/battery/ Pulser circuit & info
http://acs.comcen.com.au/batterypulser.html Pulser circuit & info
http://www.vdcelectronics.com/desulphation.htm Sulphation info
http://www.rcbatteryclinic.com/menu.htm RC Battery charging info
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Service Life - Capacity vs Use for Common Batteries
Life ?
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Trends in Cell Technology Product Life Cycles
Newer rechargeable technologies are gaining share in the marketplace as
older technologies have reached maturity and are being used in fewer new
product designs. Knowledge of the marketplace trends helps in selecting
the proper cell technology for the optimum cost-benefit scenario. It is
important to consider the energy system components' life cycle and
compare it to the life cycle of the end product.
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CONCLUSION








Observe recommended precautions for use and disposal of all battery types.
Discard “sealed” cells that show definite signs of leakage.
For Ham purposes NiCad, Lead Acid (GelCell), NiMH and Alkaline, are most
practical. Lithium batteries require a matched smart charger and all chemistries
benefit from a smart charger.
Battery Life (rechargeable) is directly related to temperature, and
discharge/charge patterns.
The most economical operation results from selecting quality batteries and
following recommend usage guidelines and charging procedures.
Occasional “refreshing” (discharging to nominal discharge level and
recharging) and finishing off the charge cycle with a trickle charge can
enhance the life of NiCad and NiMH batteries. (Not SLA)
Batteries within the same family can have important differences.
Don’ts:
–
–
–
–
–
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Do not short
Do not solder unless solder tabs are available
Do not over charge
Do not allow an SLA to remain in a discharged state
Do not believe everything you hear or read on the Internet.
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