A Brief Course in Electrochemical Energy Storage

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A Brief Course in Electrochemical Energy Storage

• Bob Nuckolls
• Sr. Engineer/SME
• Raytheon Aircraft Company
• Rev -B- 27 July 2004

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Copies of this Power Point presentation may be
downloaded fromaeroelectric.com/ppt/Battery_Pre
sentation_D

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A little history . . .

• 1800 Volta demonstrates to Napoleon the Volta
  pile, a primary, non rechargeable battery.
• 1854 Sinstede uses the first time lead plates in
  sulfuric acid to store i.e. accumulate,
  electricity.
• 1859 Planté improves the capacity of the lead
  acid batteries with a technique still in use
  today.
• 1881 Faure discovers the pasted plate which
  yields a major breakthrough in capacity. A lead
  antimony alloy is used the first time to give
  strength.
• 1882 Gladstone and Tribe describe the so called
  double-sulfate theory i.e. the basis of operation
  of the lead acid battery. Tudor operates a lead
  acid battery factory in Luxembourg.
• 1899 Jungner invents nickel cadmium rechargeable
  battery. Expensive and limited in useage. New
  electrodes developed 1930s. 1940s brought a
  sealed nickel cadmium battery that recombines
  internal gases produced during charge.
  Improvements have been made every decade since.

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A little history . . .

• 1907 A lead calcium alloy is patented.
• 1910 The iron-clad or tubular plate construction
  is introduced
• 1915 Willard introduces rubber separators.
• 1918 Shimazu describes the ball mill oxide.
• 1951 Lead calcium alloys are used in telephone
  exchange stationary lead acid batteries.
• 1958 Jache describes the gel valve-regulated,
  sealed lead-acid battery.
• 1965 Polypropylene sealed lead-acid battery cases
  start to be used.
• 1968 The maintenance free sealed lead-acid
  battery is developed by Gates.
• 1980 Stationary valve-regulated, sealed lead-acid
  batteries based on AGM technology are developed

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A little history . . .

• Primary Cells
• One shot energy sources . . . Chemistry is not
  reversible
• Typical products Carbon-Zinc, Zinc-Air,
  Manganese-Dioxide (alkaline)

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A little history . . .

• Carbon-Zinc Evolved from Leclanchés 1866
  patent on a wet cell design using a liquid,
  ammonium chloride electrolyte. A dry cell version
  of the Leclanché cell was developed and perfected
  in the 1880s. The carbon zinc dry cell remains
  much the same to this day.

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A little history . . .

• Duracell pioneered the Alkaline Manganese Dioxide
  electrochemical system nearly 40 years ago.
• Alkaline cells have higher energy output than
  zinc-carbon predecessors.
• Other significant advantages are
• Longer shelf life
• Better leakage resistance
• Superior low temperature performance.

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A little history . . .

• Secondary Cells
• Chemistry can be reversed by forcing energy back
  into the cell via external power supply
  (charger).
• Typical products Lead-Acid, Ni-Cad, Ni-Mh,
  Lithium Ion

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A little history . . .

• Lead-Acid A very successful technology with over
  120 years of commercial service.

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A little history . . .

• Ni-Cad Nearly as mature as the Lead-Acid
  battery, Ni-Cads were the first to offer
  drip-free, sealed energy storage technology.

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A little history . . .

• Nickel Metal Hydride Chemically, one of the best
  cathode materials for battery cells would be
  hydrogen. Discoveries in late 1960s showed that
  some metal alloys had the ability to store atomic
  hydrogen 1000 times their own volume.
• NiMh technology is rapidly replacing
  Nickel-Cadmium as the portable power
  cell-of-choice.

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Electrochemical Energy Storage Basics(Its all
in the cells!)
What is a cell?
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What is a cell?
Definition of Cell Anode - Source of electron
flow to the outside. Cathode - Sink for electron
flow from the outside. Electrolyte - Media for
the exchange of ions in reduction-oxidation
reactions at anode and cathode.
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What is a cell?
Every material in the universe has a position on
the ladder of values for Electromotive Force when
compared with other materials . . . Lets explore
the comparative differences between a rudimentary
cell using silver-copper and silver-aluminum
electrodes . . .
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What is a cell?
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What is a cell?
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What is a cell?
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What is a cell?
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What is a cell?
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What is a cell?
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What is a cell?
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What is a cell?
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What is a cell?
Classic classroom electrolysis demonstration . .
. The Lemon Cell.
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What is a cell?
Construction typical of all flooded and gelled
lead-acid cells. A battery is a array of
series connected cells (higher voltage) or
parallel connected cells (higher capacity /
current)
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What is a cell?
An array of cells assembles into a battery . . .
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What is a cell?
Cutaway of Gates/Hawker/Enersys jelly roll
cells which introduced recombinant gas, lead-acid
technology to the marketplace in the late 60s.
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What is a cell?
Gel-Cell Not! Prismatic VRSLA cells followed
closely on the heels of Gates Cyclon series
jelly-roll cells. The vent regulated, sealed
lead-acid (VRSLA), recombinant-gas (RG), absorbed
glass mat (AGM) products proliferated. Prismatic
cells are available in sizes from 0.5 to 1200
a.h. These are manufactured in the millions for
emergency lighting, portable power,
un-interruptible power supplies, etc. etc
Cells of these batteries contain so little liquid
that you can drive a nail into them, pull it out,
and they will not leak.
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What is a cell?
Ni-Cad and Ni-Mh jelly-roll construction.
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Lead-AcidElectrochemical Energy Storage Basics
Lead-Acid How it works . . .
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Lead Acid how it works . . .
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Lead Acid how it works . . .
The chemical reaction during normal lead-acid use
is Pb PbO2 lt-----gt 2PbSO4 H2O 2
electrons Fortunately the reaction proceeds
readily in either direction without much heat.
The chemistry usually is written as two half cell
reactions which makes it a little more clear just
what is happening at each plate At the anode
PbO2 4H 2 electrons---gt PbSO4
2H2O At the cathode Pb(metal) ---gt PbSO4 2
electrons (Equations above are not balanced) As
the battery discharges more water is produced
which forces specific gravity of electrolyte
lower.
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Lead Acid how it works . . .
During cell over-charge there is no more
lead-sulfate left on the plates to be oxidized
and reduced. Current forced through a solution
must produce a reaction at both electrodes. Since
all materials used to store electrical energy has
been completely oxidized or reduced (charged)
something else happens. Further, its not good
for the battery and could generate a hazardous
condition. The net reaction in the battery
during overcharge is 2H2O 4 electrons ----gt
2H2 O2
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Lead Acid how it works . . .

• There are two basic cell types flooded-vented
  and starved-sealed.
• Flooded cell batteries require vents to
  atmosphere so that loose hydrogen and oxygen
  gases generated during charging are vented from
  the cell.
• Recombinant gas or immobilized electrolyte cells
  keep a grip on evolved gasses Oxygen generated
  from the positive electrode during charging
  diffuses to the negative electrode where it
  recombines to form water
• The recombination reaction suppresses hydrogen
  evolution at the negative electrode so that the
  cell may be sealed to atmosphere.
• In practice, the recombination efficiency is not
  100. Therefore, a pressure relief valve limits
  internal pressure to a relatively low value on
  the order of 2 psig.
• Sealed lead-acid cells may be called
  valve-regulated lead-acid (VRLA) cells.

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Lead-AcidBattery Fabrication
Lead-Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
Buttered plates are stacked and then cured for
two weeks in a temperature-humidity controlled
environment.
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
At this point, the capped battery sits overnight
for sealing epoxy to set up. Battery is pressure
tested on a cell-by-cell basis. Any detected
leakage is cause for rejection.
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication

• Cast lead plates (1 calcium reduces water loss)
• Apply paste positive and negative plates
• Aged two weeks
• Insulated and sleeved
• Soldered into temporary battery array
• Charge individual plates
• Group sets of () and (-) plates for assy and
  then group again for weight matching.
• Molded plastic cases and tops
• Install sets of plates in battery box.

• Weld risers onto plate arrays
• Hand-weld crossovers and terminal straps
• Epoxy grooves in lid and set battery upside down
  into lid
• Pressure test. If pressure test fails, battery
  is scrap.
• 7x Deep cycle charge and capacity tests
• Pour out excess electrolyte
• Cap and wash
• Ip Test
• Elapse Time 6 weeks!

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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
Exploded view of a Concord lead-acid aircraft
battery . . .
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
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Lead Acid Battery Fabrication
Concord Labor intensive. 160 employees
fabricate 1000 units a day Lead Calcium Alloy
Plates Cast Plates, cast pockets for active
material An array of plates are weighed on
cell-by-cell basis for capacity matching. Sets of
plates are relatively loose fit in battery box
and placed individually by hand before inter-cell
connections are hand welded.
Enersys (Hawker) Highly automated 560 employees
fabricate 60,000 units a day Pure Lead
Plates Plates punched from long rolls of
chill-cast lead sheet No porous plastic pocket
over plate structure. AGM is only separator. Sets
of plates are hydraulically compressed and pushed
into tight fitting boxes by machine. Inter-cell
connections are spot welded
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Lead Acid Battery Fabrication
Concord cont. Dry charged cells are flooded and
electrically cycled to insure saturation of
separators. Cells are sealed after excess
electrolyte is poured out at the conclusion of
deep cycle activation and testing. Manufacturing
cycle 6 weeks
Enersys (Hawker) cont. Electrolyte vacuum
injected in precise amounts and cells are
immediately sealed. Battery is activated during
first charge cycle. Manufacturing cycle 5
weeks. Cost approx 2x that of comparable Concord
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Lead Acid Battery Fabrication

• Coming over the hill . . .
• Concord has patented a new process for making
  lighter grid plates.
• Lead-clad ALUMINUM plates are being perfected.
  Chemically, these perform light lead but offer
  lighter structure, stiffer plates and better
  conductivity.
• This process promises substantial reductions in
  battery weight by something on the order of 20.
• Recycling is more difficult . . . Aluminum does
  NOT mix well with lead in a smelting operation.
  These new products will CANNOT utilize the
  current recycle stream for lead-acid batteries.

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Lead-Acid Battery Operation
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Lead Acid Battery Operation

• Batteries in airplanes serve three major
  functions
• Crank engine(s). This is a relatively high
  power/low energy (perhaps 5 to 15 of batterys
  total charge is needed to get a turbine engine
  started. Even less for a piston engine.
• Filter / stabilize the operating system. The
  batterys low internal impedance provides the
  best filter for alternator / generator noise.
  Also, some alternators do not run well without a
  battery on line.
• Standby power in case of engine driven source
  failure. Here the battery must be sized and
  maintained to assure duration of operation of
  equipment essential for descent to landing.

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Lead Acid Battery Operation

• Engine Cranking . . .
• Getting the engine started is certainly a
  high-power event. Currents delivered by the
  battery at the beginning of a turbine start cycle
  is on the order of 700 to 1000 Amps. It tapers to
  about 300 Amps at the end of a 20-30 second start
  cycle.
• While the current levels are high, total energy
  removed from the battery is a fraction of the
  battery total. The 200,000 watt-second start
  curve illustrated next represents less than 10
  of typical batterys 3,000,000 watt-second
  capacity.
• Reciprocating engines start in a much shorter
  period of time on the order of 5-10 seconds . . .
  Average current during the start cycle is 200-300
  Amps.
• A reciprocating engine takes about 40,000
  watt-seconds, about 4 of the batterys capacity.
• While power levels are high, total energy
  requirements are rather modest.

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Lead Acid Battery Operation
Beechjet Start Curve Piecemeal Integration
Shows 200Kw/Sec Start Cycle
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Lead Acid Battery Operation
The importance of controlling internal and
external impedance . . .
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Lead Acid Battery Operation
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Lead Acid Battery Operation
Each cell can be visualized as many hundreds of
individual cells-sites in parallel . . . Each one
contributing a small energy storage
capability and a moderately high source
impedance. E.g. A cell of 1000 cell-sites having
individual source impedance of 1 ohm combine to
make a single cell with a source impedance of
1 milliohm. When half of the cell sites die,
capacity drops by half and source impedance
doubles.
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Lead Acid Battery Operation
Effects of internal impedance become apparent
when we consider energy delivered to the external
world at various discharge rates. Here are
typical discharge curves at 25C for a 24 Volt,
37 Ah VSLA aircraft battery.
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Lead Acid Battery Operation

• Standby Power. . .
• This is the batterys toughest task . . . Most
  production aircraft with a standby power storage
  requirement call for 30 minutes of operation sans
  engine driven power sources.
• Unlike engine cranking, emergency operations are
  all but guaranteed to tax the batterys capacity
  to the limit.
• Unfortunately, battery capacity cannot be gauged
  from outside the battery without doing an actual
  capacity test.

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Lead Acid Battery Operation
Portable capacity tester/chargers do exist but
theyre not the kind of thing you find in the
average mechanics tool box!
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Lead Acid Battery Operation
Ideal charging voltage for a battery is
temperature dependent. Unfortunately, the only
known temperature compensated regulators for
aircraft applications are available only to the
owner-built and maintained (OBAM) aircraft
community.
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Lead Acid Battery Operation
Lacking the elegant solution regulator, the
best compromise is to make maintenance
adjustments of bus voltage depending on current
climatic operating conditions. The following
recommendations come from Concords user guide on
lead-acid battery application.
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Lead Acid Battery Operation
The ideal battery charging philosophy maintains
voltage commensurate with present battery
temperature until recharge rate drops to less
than 1A at the whereupon voltage should be
stepped down to something on the order of 13.5
(27.0) volts.
A stepped down maintenance voltage would be just
high enough to prevent loading the battery but
too low to put any significant charge on the
battery. This charging philosophy would promise
nearly ideal battery service life by offering
fastest practical recharge while protecting the
battery from overcharging.
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Care and Feeding of Lead-Acid Batteries
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Care and Feeding of Lead Acid Batteries . . .

• A comprehensive study was recently conducted at
  RAC to determine why we were suffering large
  warranty losses on batteries installed in
  customer aircraft.
• The study looked at end-to-end battery handling
  issues from the time a cell plate is fabricated
  until a battery is no longer suited for service.
• A major fraction of the costs were traced to
  poor warranty policy . . . RAC warranty was set
  to a value much greater than the battery
  manufacturers warranty. Most of the cash bleed
  was fixed with a more realistic battery warranty
  policy.
• The study identified a number of areas where
  battery handling can be improved.
• Take advantage of just-in-time deliveries
  offered by battery manufacturers to reduce number
  of batteries in inventory -AND- time that
  batteries sit on the shelf.
• Concentrate battery delivery and storage in
  smaller area. A survey of SAP showed that we had
  batteries in storage in dozens of different
  places on the square mile.

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Care and Feeding of Lead Acid Batteries . . .

• Reduce numbers of folk who need to touch
  batteries. Individuals who dont handle
  batteries dont need to be trained or provided
  with tools and work-orders to accommodate a
  batterys special needs. Cost of ownership and
  risks go down.
• Vast majority of handling induced battery
  failures on square mile occur either on
  experimental flight test aircraft or batteries
  neglected in storage.
• Most production lines already use tool
  batteries . New policies and procedures have
  been developed to store customer batteries in
  racks at the end of assembly lines.
• Tool batteries will be used until aircraft is
  ready for delivery to flight test.
• Number of storage locations for batteries on the
  square mile reduced to a tiny fraction of the
  current condition.
• Few opportunities for improvement were
  identified after the customer battery was
  installed on the aircraft Battery failure rates
  from time-of-installation to time-of-delivery was
  quite low . . .

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Care and Feeding of Lead Acid Batteries . . .

• Opportunities for improvement
• Work with field service organizations to avoid
  handling damage on replacement batteries.
• New policies and procedures for ordering stock
  warehousing.
• Develop first-in-first-out handling procedures.
• Develop monitoring techniques for ALL
  life-limited parts including batteries.
• Acquire tools and conduct training for battery
  maintenance where there is a demonstrable return
  on investment.
• Conduct training for folks who handle batteries
  to improve awareness of the fragile nature of
  stored batteries.
• Work with manufacturers to improve data
  gathering on field failures. This same data
  offers a fall-out opportunity to improve battery
  performance based on real-life numbers on how
  aircraft batteries are used. More on this later.

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Lead Acid Battery Operation

• Long Term Battery Storage
• A number of conditions affect the magnitude of
  leakage current in batteries.
• Storage temperature
• Batteries stored in warm climes and un-controlled
  warehouse environments are especially subject to
  increased rates of leakage discharge. Batteries
  stored in Canadian warehouses do very well.
• Free oxygen dissolved in the electrolyte.
• When a cell is sealed off from the environment,
  the percentage of dissolved gasses in the
  electrolyte drops to a very low value. This
  simple isolation of the cell environment from
  ambient atmosphere results in markedly low self
  discharge rates.
• VSLA batteries can be stored at moderate
  temperatures for many months.

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Lead Acid Battery Operation

• Long Term Battery Storage (cont)
• Batteries in warehouses tend to be stored in
  ready-to-ship cartons or crates.
• This works directly against any efforts to
  monitor or maintain batteries on the shelf.
• Any stocking operation that intends to keep
  zero-time batteries in long-term storage (6
  months or more) would do well to store them out
  of the crate and connected to some form of
  battery-tending power supply to offset
  self-discharge characteristics inherent in all
  batteries.

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Lead Acid Battery Operation
Long Term Battery Storage EVERY battery suffers
from some degree of internal self-discharging
leakage. This manifests itself as a low level
load on the battery that will eventually
produce a totally discharged battery.
A Battery Tender type of smart charger will
charge initially at some level that insures a
charge top-off . . . Something on the order of
14.4/28.8 volts. When charge acceptance current
drops below some small value, the output voltage
drops to 13.0/26.0 volts so that the Battery
Tender exactly offsets the leakage currents.
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Lead Acid Battery Operation
0.75A Battery Tender from Deltron
(www.batterytender.com)
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Lead Acid Battery Operation
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Lead Acid Battery Operation
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Value Assessment of Concord vs..
Enersys(Getting Past the Marketing Hype . . .
Beware of Pink Bunnies)
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Getting Past the Marketing Hype . . .
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Getting Past the Marketing Hype . . .
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Getting Past the Marketing Hype . . .
Performance of various AA cell brands at room temp
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Getting Past the Marketing Hype . . .
Alkaline vs.. Photo Lithium at Room Temp and -20C
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Getting Past the Marketing Hype . . .

• Bottom line of study on AA Alkaline batteries
  Irrespective of intensity and flavor of marketing
  hype, the best isnt a lot better than the
  worst and the lowest cost is not the worst
  yet offers the best value.
• We know that lead-acid capacity is a function of
  mass of reactants. Lead, lead-oxide, sulfuric
  acid, water, lead-sulfate, and to some lesser
  degree, mini-reactions that affect
  charge/discharge efficiency and water loss. Just
  how bad can a lead-acid battery be?
• Greater number of thinner, pure lead plates has
  an obvious advantage in terms of lowering
  internal impedance of the cells but since most of
  our customers are obligated to set service life
  based on capacity, is there a cost-of-ownership
  advantage to the higher cost of thin, pure-lead
  plates?
• A question yet to be answered is whether the
  premium construction of an Enersys (Hawker)
  battery translates directly into additional
  service life commensurate with the increased cost
  of the battery.

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Getting Past the Marketing Hype . . .

• Current best recommendation for the Owner Built
  and Maintained Aircraft (OBAM) community is to by
  the least expensive product you can find and
  change it out often . . . Like every annual
  inspection.
• For light aircraft running dual batteries, this
  means that you can put a new battery in the main
  battery slot every year and rotate the main
  battery into the auxiliary battery slot.
• For a cost of about 40/year
• The main battery is less than 1 year old and
  its stand-by capacity is assured.
• There are no batteries more than 2 years old and
  the auxiliary battery can be depended on for
  backing up a light, ignition load (2A or so) for
  duration of fuel aboard.
• Two batteries in parallel offer 34 a.h. cranking
  performance for superior engine starting.

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Getting Past the Marketing Hype . . .

• The jury is still out on battery brand selection
  philosophy (Concord versus Hawker) based on
  real-number economics and physics.
• There is consideration for developing a black
  box for aircraft batteries.
• A small (0.5 x 1.0 x 2.0) module mounted in
  the head-space of the battery would measure and
  record voltage and temperature every 10 seconds
  for two years.
• When a battery is taken out of service, the
  black box can be easily removed and sent back
  to manufacturer for evaluation. One can easily
  deduce number of flights, number and difficulty
  of engine starts. If, when and for how long a
  battery was deeply discharged and stored in a
  discharged state, etc.
• A battery taken out of service need not be
  shipped to a remote location for evaluation. The
  maintenance technician needs only to return the
  black box. Battery is recycled locally.

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Getting Past the Marketing Hype . . .

• The cost of the black box may well be less than
  cost of shipping a battery.
• When batteries are pulled for warranty
  adjustment, the manufacturer would have hard data
  on potential abuse of the battery.
• A parallel program to offer credit on new
  battery by returning the black box would
  encourage field participation data gathering for
  product improvement studies.
• Same device might include an LED warning light
  that illuminates below 25.0 volts . . . Battery
  in storage can say Charge Me!

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Getting Past the Marketing Hype . . .

• There is substantial anecdotal information
  suggesting that a major source of battery-killing
  stress in field is failure to shut of hot-battery
  bus accessories in some models. This will run the
  battery down completely. Batteries stored in this
  condition are VERY difficult to recover. The
  battery black box would record these events.
• When the battery makes it past the warranty
  period, data gleaned would provide hard data
  feedback on battery performance and battery
  usage. This type of information would be
  invaluable to the manufacturer in making process
  tweaks to design to maximize performance.
• This data would also cut through the fog of
  marketing hype and permit considered
  recommendations of one brand over another with
  respect to overall battery performance and best
  value for cost-of-ownership issues.
• At this time Its not clear that capacity based,
  service life of pure-lead, thin-plate Enersys
  products will outperform Concord cast-plate
  products a factor of 21

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Summation on Batteries . . .

• Batteries are like houseplants Peak performance
  is achieved with optimized control of deleterious
  and helpful environmental conditions.
• When a battery is fully discharged and allowed
  to sit, irreversible damage MAY result . . . Not
  all batteries can be recovered from this kind of
  abuse.
• Service life is strongly influenced by owner,
  pilot and maintenance behavior. A battery
  likes to be moderately challenged often.
  Batteries stored for long periods of time will do
  better with considered attention . . . Like
  Battery Tenders.

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Missed Opportunities . . .

• The aviation design community has been aware of
  the temperature dependence of lead-acid batteries
  and temperature criticality of nickel-cadmium
  batteries for a very long time.
• However, there have been no development
  programs that specify generator and alternator
  control units to extend battery life and reduce
  maintenance costs.
• Accessories that run from hot-battery busses
  should be fitted with auto-shutoff timers or
  other technology designed to protect batteries
  from accidental total discharge.
• There may be value for OEM airframe engineers
  and field service personnel to participate in
  promoting and implementing installation and
  recovery of black boxes on aircraft batteries.
• There is value in crafting and presenting
  familiarization courses and published materials
  to elevate all user awareness of the unique
  characteristics of aircraft batteries.

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A Brief Course in Electrochemical Energy Storage
The End