Ennetech by Erasmus and Kinkajou Authors

 

 

Erasmus and Kinkajou share their vision of technologies that will help us on our way.

Primary & Secondary Batteries

 

 

KinkajouKinkajou

 

Primary & Secondary (Rechargeable) batteries have differing performance characteristics.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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The next chart illustrates the number of pictures a digital camera can capture with discharge pulses of 1.3 watts on different types of batteries in an AA format. (With two cells in series at 3V, 1.3W draws 433mA.) The clear winner was Li-FeS2 (Lithium AA) with 690 pulses; the second was NiMH with 520 pulses and the distant third was standard alkaline producing only 85 pulses. Internal resistance rather than capacity governs the shot count.

Battery Durability Battery Durability

 

ILLUSTRATION

Figure : Number of shots a digital camera can take with Alkaline NiMH and Lithium

Li-FeS2, NiMH and Alkaline have similar capacities; the internal resistance governs the shot count on a digital camera.  

What follows is a regard chart showing a digital camera with a 1.3 what load using a variety of batteries.

Battery Performance Battery Performance

 

ILLUSTRATION
Ragone chart illustrates battery performance with various load conditions.



Energy = Capacity x V
Power = Current x V

Inserting A Battery Inserting A Battery

 


Battery chemistry

Primary batteries and their characteristics

Chemistry

Anode (−)

Cathode (+)

Max. voltage, theoretical (V)

Nominal voltage, practical (V)

Specific energy(MJ/kg)

Elaboration

Shelf life at 25 °C, 80% capacity (months)

Zinc–carbon

Zn

MnO2

1.6

1.2

0.13

Inexpensive.

18

Zinc–chloride

1.5

Also known as "heavy-duty", inexpensive.

Alkaline
(zinc–manganese dioxide)

Zn

MnO2

1.5

1.15

0.4–0.59

Moderate energy density.
Good for high- and low-drain uses.

30

Nickel oxyhydroxide
(zinc–manganese dioxide/nickel oxyhydroxide)

1.7

Moderate energy density.
Good for high drain uses.

Lithium
(lithium–copper oxide)
Li–CuO

1.7

No longer manufactured.
Replaced by silver oxide (IEC-type "SR") batteries.

Lithium
(lithium–iron disulphide)
LiFeS2

Li

FeS2

1.8

1.5

1.07

Expensive.
Used in 'plus' or 'extra' batteries.

337

Lithium
(lithium–manganese dioxide)
LiMnO2

3.0

0.83–1.01

Expensive.
Used only in high-drain devices or for long shelf-life due to very low rate of self-discharge.
'Lithium' alone usually refers to this type of chemistry.

Lithium
(lithium–carbon fluoride)
Li–(CF)n

Li

(CF)n

3.6

3.0

120

Lithium
(lithium–chromium oxide)
Li–CrO2

Li

CrO2

3.8

3.0

108

Mercury oxide

Zn

HgO

1.34

1.2

High-drain and constant voltage.
Banned in most countries because of health concerns.

36

Zinc–air

Zn

O2

1.6

1.1

1.59

Used mostly in hearing aids.

Zamboni pile

Zn

Ag or Au

0.8

Very long life
Very low (nanoamp, nA) current

>2,000

Silver-oxide (silver–zinc)

Zn

Ag2O

1.85

1.5

0.47

Very expensive.
Used only commercially in 'button' cells.

30

Magnesium

Mg

MnO2

2.0

1.5

40

 

 

 

Battery Chargers Electronic Circuitry Battery Chargers Electronic Circuitry

Secondary Batteries

Secondary (rechargeable) batteries and their characteristics

Chemistry

Cell
voltage

Specific energy
(MJ/kg)

Comments

NiCad

1.2

0.14

Inexpensive.
High-/low-drain, moderate energy density.
Can withstand very high discharge rates with virtually no loss of capacity.
Moderate rate of self-discharge.
Environmental hazard due to Cadmium – use now virtually prohibited in Europe.

Lead–acid

2.1

0.14

Moderately expensive.
Moderate energy density.
Moderate rate of self-discharge.
Higher discharge rates result in considerable loss of capacity.
Environmental hazard due to Lead.
Common use – Automobile batteries

NiMH

1.2

0.36

Inexpensive.
Performs better than alkaline batteries in higher drain devices.
Traditional chemistry has high energy density, but also a high rate of self-discharge.
Newer chemistry has low self-discharge rate, but also a ~25% lower energy density.
Used in some cars.

NiZn

1.6

0.36

Moderately inexpensive.
High drain device suitable.
Low self-discharge rate.
Voltage closer to alkaline primary cells than other secondary cells.
No toxic components.
Newly introduced to the market (2009). Has not yet established a track record.
Limited size availability.

AgZn

1.86
1.5

0.46

Smaller volume than equivalent Li-ion.
Extremely expensive due to silver.
Very high energy density.
Very high drain capable.
For many years considered obsolete due to high silver prices.
Cell suffers from oxidation if unused.
Reactions are not fully understood.
Terminal voltage very stable but suddenly drops to 1.5 volts at 70–80% charge (believed to be
due to presence of both argentous and argentic oxide in positive plate – one is consumed first).
Has been used in lieu of primary battery (moon buggy).
Is being developed once again as a replacement for Li-ion.

Lithium ion

3.6

0.46

Very expensive.
Very high energy density.
Not usually available in "common" battery sizes.
Very common in laptop computers, moderate to high-end digital cameras, camcorders, and cell phones.
Very low rate of self-discharge.
Tends to require either user awareness or a dedicated management system to slow down the gradual loss of capacity.
Terminal voltage unstable (varies from 4.2 to 3.0 volts during discharge).
Volatile: Chance of explosion if short-circuited, allowed to overheat, or not manufactured with rigorous quality standards.


Lithium Ion Batteries Lithium Ion Batteries

KinkajouKinkajou : Give us a Comparison of Secondary Batteries Characteristics

ErasmusErasmus : Select between maximum runtime, long service life, small size and low cost.



The most common rechargeable batteries are Lead acid, NiCad, NiMH and Li-ion. These batteries have very different properties. It is important to select a battery whose properties match the application in which they are used. Typical variables are specific energy (Wh/ kilogram), discharge recharge cycle life, % self discharge per month, charging time, peak output current or power, maintenance requirements, voltage and environmental toxicity. Cost is also a major factor, the older technologies such as lead acid generally being cheaper.

ErasmusErasmus :

Lead Acid – Lead acid batteries are more forgiving of poor maintenance practices. They do have a low specific energy and limited cycle life. They typically used in small mobile vehicles such as scooters and uninterruptible power supplies (UPS). Lead is toxic and cannot be disposed in landfills. (Absorbent Glass Mat) is a major battery type in the lead acid family and lead acid with carbon additives are making progress by allowing faster charge and increasing cycle life).Secondary Lead Acid Battery Secondary Lead Acid Battery
 

Nickel-cadmium – NiCad is typically used where long service life and high discharge current are required. NiCad tolerate high workloads is very well NiCad batteries are very tolerant of ultrafast charging. Due to environmental concerns, NiCad is toxic and cannot be disposed in landfills.
 

Nickel-metal-hydride –NiMH has only mildly toxic metals and provides higher specific energy capacity. NiMH is also available in AA and AAA battery cells for consumer use.
 

ErasmusErasmus :  Lithium-ion, Li-ion needs a protection circuit to minimise battery discharge. A fully discharged lithium ion battery becomes essentially unusable. They need to be stored approximate 40% charge. They do however have minimal long-term self discharge. The traditional Li-ion systems are cobalt, manganese and phosphate. There are other lithium- ion rechargeable battery systems under development. The most common format of lithium-ion batteries is the 18650 cell which measures 18 mm in diameter and is 65 mm long. The cells are usually combined in battery “packs” with different output currents and voltages. Lithium ion batteries in the 18650 cell format can also be modified to deliver either high-capacity, high power output or a hybrid format delivering both requirements. The cells can also be modified for extended temperature range tolerance and long discharge/ recharge cycle counts.
The major reason for switching to the Li-ion polymer is form factor. It allows wafer-thin geometries, a style that is demanded by the highly competitive mobile phone industry.

Lithium Buton Batteries Lithium Buton Batteries

 

 

ErasmusErasmus : 
Advantages and Limitations of Li-ion Polymer Batteries

Advantages

Very low profile — batteries that resemble the profile of a credit card are feasible.

Flexible form factor — manufacturers are not bound by standard cell formats. With high volume, any reasonable size can be produced economically.

Light weight – gelled rather than liquid electrolytes enable simplified packaging, in some cases eliminating the metal shell.

Improved safety — more resistant to overcharge; less chance for electrolyte leakage.

Limitations

Lower energy density and decreased cycle count compared to Li-ion — potential for improvements exist.

Expensive to manufacture — once mass-produced, the Li-ion polymer has the potential for lower cost. Reduced control circuit offsets higher manufacturing costs.




The high cell voltage allows battery packs with only one cell. Most of today’s mobile phones run on a single cell, an advantage that simplifies battery design. To maintain the same power, higher currents are drawn. Low cell resistance is important to allow unrestricted current flow during load pulses.

The Li-ion is a low maintenance battery, an advantage that most other chemistries cannot claim. There is no memory and no scheduled cycling is required to prolong the battery’s life. In addition, the self-discharge is less than half compared to NiCad.

 



Lithium Ion Polymer (Li-ion polymer) — offers the attributes of the Li-ion in ultra-slim geometry and simplified packaging. Main applications are mobile phones.

For ultra-slim geometry (less than 4 mm), the only choice is Li-ion polymer. This is the most expensive system in terms of cost-to-energy ratio. There are no gains in energy density and the durability is inferior to the rugged 18560 cell.

 

 

 

ErasmusErasmus :
Advantages and Limitations of Li-ion Batteries

Advantages

High energy density — potential for yet higher capacities.

Relatively low self-discharge — self-discharge is less than half that of NiCad and NiMH.

Low Maintenance — no periodic discharge is needed; no memory.

Limitations

Requires protection circuit — protection circuit limits voltage and current. Battery is safe if not provoked.

Subject to aging, even if not in use — storing the battery in a cool place and at 40 per cent state-of-charge reduces the aging effect.

Moderate discharge current.

Subject to transportation regulations — shipment of larger quantities of Li-ion batteries may be subject to regulatory control. This restriction does not apply to personal carry-on batteries.

Expensive to manufacture — about 40 per cent higher in cost than NiCad. Better manufacturing techniques and replacement of rare metals with lower cost alternatives will likely reduce the price.

Not fully mature — changes in metal and chemical combinations affect battery test results, especially with some quick test methods.




The most basic safety device in a battery is a fuse that opens on high current. Some fuses open permanently and render the battery useless; others are more forgiving and reset. The positive thermal coefficient (PTC) is such a re-settable device that creates high resistance on excess current and reverts back to the low ON position when the condition normalizes. A third method is a solid-state switch that measures current and voltage and disconnects the circuit if either value is too high. The protection circuits of Li-ion work on this basis.

All switching devices have a residual resistance, which causes a slight increase in overall battery resistance and a subsequent voltage drop.

 


ErasmusErasmus :  The Nickel Cadmium (NiCad) battery

The NiCad prefers fast charge to slow charge and pulse charge to DC charge. All other chemistries prefer a shallow discharge and moderate load currents. The NiCad is a strong and silent worker; hard labour poses no problem. In fact, the NiCad is the only battery type that performs well under rigorous working conditions. It does not like to be pampered by sitting in chargers for days and being used only occasionally for brief periods. A periodic full discharge is so important that, if omitted, large crystals will form on the cell plates (also referred to as memory) and the NiCad will gradually lose its performance.

Among rechargeable batteries, NiCad remains a popular choice for applications such as two-way radios, emergency medical equipment and power tools. Batteries with higher energy densities and less toxic metals are causing a diversion from NiCad to newer technologies.

 

 

ErasmusErasmus :

   Advantages and Limitations of NiCad Batteries

Advantages

Fast and simple charge — even after prolonged storage.

High number of charge/discharge cycles — if properly maintained, the NiCad provides over 1000 charge/discharge cycles.

Good load performance — the NiCad allows recharging at low temperatures.

Long shelf life – in any state-of-charge.

Simple storage and transportation — most airfreight companies accept the NiCad without special conditions.

Good low temperature performance.

Forgiving if abused — the NiCad is one of the most rugged rechargeable batteries.

Economically priced — the NiCad is the lowest cost battery in terms of cost per cycle.

Available in a wide range of sizes and performance options — most NiCad cells are cylindrical.

Limitations

Relatively low energy density — compared with newer systems.

Memory effect — the NiCad must periodically be exercised to prevent memory.

Environmentally unfriendly — the NiCad contains toxic metals. Some countries are limiting the use of the NiCad battery.

Has relatively high self-discharge — needs recharging after storage.

Figure: Advantages and limitations of NiCad batteries. 

 

ErasmusErasmus :Driven by different applications, two battery designations emerged. They are the small sealed lead acid (SLA); also known under the brand name of Gelcell, and the large valve regulated lead acid (VRLA). Technically, both batteries are the same. (Engineers may argue that the word ‘sealed lead acid’ is a misnomer because no lead acid battery can be totally sealed.) Because of our emphasis on portable batteries, we focus on the SLA.

ErasmusErasmus : Unlike the flooded lead acid battery, both the SLA and VRLA are designed with a low over-voltage potential to prohibit the battery from reaching its gas-generating potential during charge. Excess charging would cause gassing and water depletion. Consequently, these batteries can never be charged to their full potential.

 



KinkajouKinkajou : So tell us about the SLA and the VRLA !
[[small sealed lead acid (SLA); and the valve regulated lead acid (VRLA).]]

The lead acid is not subject to memory. Leaving the battery on float charge for a prolonged time does not cause damage. The battery’s charge retention is best among rechargeable batteries. Whereas the NiCad self-discharges approximately 40 per cent of its stored energy in three months, the SLA self-discharges the same amount in one year. The SLA is relatively inexpensive to purchase but the operational costs can be more expensive than the NiCad if full cycles are required on a repetitive basis.

The SLA does not lend itself to fast charging — typical charge times are 8 to 16 hours. The SLA must always be stored in a charged state. Leaving the battery in a discharged condition causes sulfation, a condition that makes the battery difficult, if not impossible, to recharge.

Unlike the NiCad, the SLA does not like deep cycling. A full discharge causes extra strain and each cycle robs the battery of a small amount of capacity. This wear-down characteristic also applies to other battery chemistries in varying degrees. To prevent the battery from being stressed through repetitive deep discharge, a larger SLA battery is recommended.

Depending on the depth of discharge and operating temperature, the SLA provides 200 to 300 discharge/ charge cycles. The primary reason for its relatively short cycle life is grid corrosion of the positive electrode, depletion of the active material and expansion of the positive plates. These changes are most prevalent at higher operating temperatures. Cycling does not prevent or reverse the trend.

The optimum operating temperature for the SLA and VRLA battery is 25°C (77°F). As a rule of thumb, every 8°C (15°F) rise in temperature will cut the battery life in half. VRLA that would last for 10 years at 25°C will only be good for 5 years if operated at 33°C (95°F). The same battery would endure a little more than one year at a temperature of 42°C (107°F).

Among modern rechargeable batteries, the lead acid battery family has the lowest energy density, making it unsuitable for handheld devices that demand compact size. In addition, performance at low temperatures is poor.

The SLA is rated at a 5-hour discharge or 0.2C. Some batteries are even rated at a slow 20-hour discharge. Longer discharge times produce higher capacity readings. The SLA performs well on high pulse currents. During these pulses, discharge rates well in excess of 1C can be drawn.

In terms of disposal, the SLA is less harmful than the NiCad battery but the high lead content makes the SLA environmentally unfriendly.

 

 

 

 

ErasmusErasmus :
Advantages and Limitations of Lead Acid Batteries

Advantages

Inexpensive and simple to manufacture — in terms of cost per watt hours, the SLA is the least expensive.

Mature, reliable and well-understood technology — when used correctly, the SLA is durable and provides dependable service.

Low self-discharge —the self-discharge rate is among the lowest in rechargeable battery systems.

Low maintenance requirements — no memory; no electrolyte to fill.

Capable of high discharge rates.

Limitations

Cannot be stored in a discharged condition.

Low energy density — poor weight-to-energy density limits use to stationary and wheeled applications.

Allows only a limited number of full discharge cycles — well suited for standby applications that require only occasional deep discharges.

Environmentally unfriendly — the electrolyte and the lead content can cause environmental damage.

Transportation restrictions on flooded lead acid — there are environmental concerns regarding spillage in case of an accident.

Thermal runaway can occur with improper charging.




Figure : Advantages and limitations of lead acid batteries. 

 

 

 

 

Table : Characteristics of commonly used rechargeable batteries. The figures are based on average ratings of commercial batteries at time of publication. Specialty batteries with above-average ratings are excluded.

Combining cobalt, nickel, manganese and aluminium raises energy density up to 250Wh/kg.

Cycle life is based on the depth of discharge (DoD). Shallow DoD prolongs cycle life.

Cycle life is based on battery receiving regular maintenance to prevent memory.

Ultra-fast charge batteries are specially made

Rechargeable Lithium Ion Battery tools Rechargeable Lithium Ion Battery tools

 

Self-discharge is highest immediately after charge. NiCad loses 10% in the first 24 hours, then declines to 10% every 30 days. High temperature and age increase self-discharge.

1.25V is traditional; 1.20V is more commonly.

Manufacturers may rate voltage higher because of low internal resistance (marketing).

Capable of high current pulses; needs time to recuperate.

Do not charge Li-ion below freezing.

Maintenance may be in the form of equalizing or topping charge to prevent sulfation.

 

Protection circuit cuts off below about 2.20V and above 4.30V on most Li-ion; different voltage settings apply for lithium-iron-phosphate.

Li-ion may have lower cost-per-cycle than lead acid.

 

 

 

 

NiCad

NiMH

Lead Acid

Li-ion

Li-ion polymer

Reusable
Alkaline

Gravimetric Energy Density(Wh/kg)

45-80

60-120

30-50

110-160

100-130

80 (initial)

Internal Resistance 
(includes peripheral circuits) in mΩ

100 to 2001
6V pack

200 to 3001
6V pack

<1001
12V pack

150 to 2501
7.2V pack

200 to 3001
7.2V pack

200 to 20001
6V pack

Cycle Life (to 80% of initial capacity)

15002

300 to 5002,3

200 to 
3002

500 to 10003

300 to 
500

503 
(to 50%)

Fast Charge Time

1h typical

2-4h

8-16h

2-4h

2-4h

2-3h

Overcharge Tolerance

moderate

low

high

very low

low

moderate

Self-discharge / Month (room temperature)

20%4

30%4

5%

10%5

~10%5

0.3%

Cell Voltage(nominal)

1.25V6

1.25V6

2V

3.6V

3.6V

1.5V

Load Current
-    peak
-    best result


20C
1C


5C
0.5C or lower


5C
0.2C


>2C
1C or lower


>2C
1C or lower


0.5C
0.2C or lower

Operating Temperature(discharge only)

-40 to 
60°C

-20 to 
60°C

-20 to 
60°C

-20 to 
60°C

0 to 
60°C

0 to 
65°C

Maintenance Requirement

30 to 60 days

60 to 90 days

3 to 6 months9

not req.

not req.

not req.

Typical Battery Cost
(US$, reference only)

$50
(7.2V)

$60
(7.2V)

$25
(6V)

$100
(7.2V)

$100
(7.2V)

$5
(9V)

Cost per Cycle(US$)

$0.04

$0.12

$0.10

$0.14

$0.29

$0.10-0.50

Commercial use since

1950

1990

1970

1991

1999

1992





Internal resistance of a battery pack varies with cell rating, type of protection circuit and number of cells. Protection circuit of Li-ion and Li-polymer adds about 100mΩ.

Cycle life is based on battery receiving regular maintenance. Failing to apply periodic full discharge cycles may reduce the cycle life by a factor of three.

Cycle life is based on the depth of discharge. Shallow discharges provide more cycles than deep discharges.

The discharge is highest immediately after charge, then tapers off. The NiCad capacity decreases 10% in the first 24h, then declines to about 10% every 30 days thereafter. Self-discharge increases with higher temperature.

 

 

Internal protection circuits typically consume 3% of the stored energy per month.

1.25V is the open cell voltage. 1.2V is the commonly used value. There is no difference between the cells; it is simply a method of rating.

Capable of high current pulses.

Applies to discharge only; charge temperature range is more confined.

Maintenance may be in the form of ‘equalizing’ or ‘topping’ charge.

Cost of battery for commercially available portable devices.

Derived from the battery price divided by cycle life. Does not include the cost of electricity and chargers.

Figures 1a, b, c and d summarize the composition of lithium, lead, nickel-based and primary alkaline batteries.

 

 

 

Lithium-ion

Cathode (positive)

Anode (negative)

Electrolyte

Material

Metal oxides derived from cobalt, nickel, manganese, iron, aluminium

Carbon based

Lithium salt in an organic solvent

Full charged

Metal oxide with intercalation structure

Lithium ions migrated to anode.

Discharged

Lithium ions move back to the positive electrode

Mainly Carbon
 

Figure 1a: Composition of Li-ion

Lead acid

Cathode (positive)

Anode (negative)

Electrolyte

Material

Lead dioxide (chocolate brown)

Grey lead, (spongy when formed)

Sulphuric acid

Full charged

Lead oxide (PbO2), electrons added to  positive plate

Lead (Pb), electrons removed from plate

Strong sulphuric acid

Discharged

Lead turns into lead sulphate at the negative electrode, electrons driven from positive plate to negative plate

Weak sulphuric acid (water-like)

Figure 1b: Composition of Lead Acid

NiMH, NiCad

Cathode (positive)

Anode (negative)

Electrolyte

Material

Nickel

NiMH: hydrogen-absorbing alloy
NiCad: Cadmium

Potassium hydroxide

Figure 1c: Composition of NiMH and NiCad