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Lithium Cell Characteristics

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Spectrum Batteries is an independent cell distributor. We typically suggest more than 1 type of cell when proposing a new battery pack/module. This section will help you to decide which cell will best fit your application.  We urge you to become familiar with the operating characteristics of cells so that you are better able to utilize them in your application. Our expert technical staff at Spectrum Batteries is available for assistance in your cell choice.

Oilfield customers specify a particular cell for their battery pack/modules after considering cell characteristics:
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  Chemistry

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  Energy Density Comparison

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  Current Capability

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  Passivation, Depassivation

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  Temperature Rating

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  Voltage

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  Resistance to shock and vibration

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  Dimensions

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  Battery Safety Information

 Chemistry - Lithium vs. Alkaline

Lithium

Lithium batteries are very attractive to the oil industry due to a combination of high energy density, high voltage, high current capability, wide temperature range, long shelf life, and stable operating voltage.  Lithium Thionyl Chloride and Lithium Sulfuryl Chloride cells are also known as liquid cathode lithium cells.

All lithium cells and batteries made with cells larger than an AA size are restricted to being transported on Cargo Aircraft Only.  An exception to this is when a cell manufacturer performs testing certifying that the cell is non-dangerous as per United Nations guidelines.

Although there are many variations of lithium cells, the following 3 types are most commonly used in the oil patch. 

Lithium Thionyl Chloride (Li/SOCL2)

Probably the most commonly used type, lithium/thionyl chloride cells have one the highest energy densities of  available battery systems.  All of our suppliers manufacture this type, and a variation of this system is available with maximum temperature ratings of 180oC and 200oC.

Lithium Thionyl Chloride 
Open Circuit Voltage3.67 V
Nominal Voltage3.4 V
Discharge ProfileFlat
Available Temp. Rating85°C, 150oC, 180oC and 200oC

Lithium Sulfuryl Chloride (Li/SO2CL2)

Although similar, this type is different from Lithium/Thionyl Chloride cells in the following ways:

  • higher energy density due to higher voltage
  • increased current capability due to higher conductivity of electrodes

A variation of this system is available with a maximum temperature rating of 165oC.
  

Lithium/Sulfuryl Chloride 
Open Circuit Voltage3.9 V
Nominal Voltage3.5 V
Discharge ProfileFlat
Max.  Avail. Temp. Rating150oC and 165oC

Alkaline (Zn/alkaline/MnO2)

Because of its low maximum temperature rating (93oC), alkaline cells have limited use in the oil patch.  However, in cooler applications, alkaline cells are an excellent choice due to their low cost, high power output, safety, and no restrictions in transportation.

Alkaline 
Open Circuit Voltage1.5 V
Nominal Voltage1.2 V
Discharge ProfileSloping
Max.  Avail. Temp. Rating93oC

Energy Density Comparison

A comparison of Energy Density for different primary battery chemistries.  This is an approximation due to manufacturer's differences in the methods used to collect this data

energydensity.jpg

Current Capability

All of the lithium cell manufacturers utilize 3 basic types of construction: Bobbin, Moderate Rate, and Spiral.  The cell construction determines the amount of common surface area between the anode (lithium) and the cathode (high surface area carbon cathode).  The amount of electrode surface area is proportional to the current capability of the cell. 

Bobbinbobbin.jpg

This type has a small common surface area between the anode and the cathode.  Basically it consists of one cylinder of cathode surrounded by one cylinder of anode material.  The low common surface area results in low rate discharge capability.  The advantages of this type of cell are its low manufacturing cost, low self discharge rate, and no safety fuse requirement.   These cells' limited current capability and the resulting effect of passivation may limit their use in high current applications.

Moderate Ratemodrate.jpg

Similar to the Bobbin style, the moderate rate, otherwise known as dual or double anode, incorporates another layer of anode material in the center of the cathode.   Although manufacturers' assembly techniques vary, the goal with this type of construction is to increase the common surface area between the electrodes so that the cell has a higher current capability than a bobbin cell.  Like a bobbin cell, this type does not generally need a safety fuse.

Spiral

Also known as jelly roll construction, spiral cells have a very large common surface area high_rate.jpgbetween the anode and the cathode; thus the current capability of these cells is very high.  Although high rate cells require safety fuses, they are able to produce enough current to satisfy most downhole tool requirements without the effects of passivation.

* VERY IMPORTANT *

Some spiral cells are case positive and some are case negative.  Caution is required when wiring into a series string not to mix polarity.

Temperature Rating

Manufacturers use various methods to design a cell chemistry in order to operate at a particular maximum temperature.  It is recommended that users specify the lowest temperature rated cell that can be safely used.  This is because higher temperature cells tend to be more expensive, and they have some performance drawbacks if the cells are used at low temperatures.

Under no circumstances should a user attempt to use a cell in an environment exceeding the temperature rating of the cell.

Voltage

Keep in mind that the operating voltage is lower than open circuit voltage. Lithium cells, depending on the load and chemistry, have an operating voltage ranging from 2.5 - 3.9 volts. Alkaline cells operate between 0.8 - 1.6 volts. While alkaline cells' voltage decreases over the length of discharge, lithium cells maintain a steady voltage until near the end of discharge.

Assembling cells in series: the voltage multiplies by the number of cells.  
Assembling cells in parallel: the current capability and capacity multiplies by the number of cells in parallel.
Voltage.jpg
ChemistryVoltage
Lithium/Thionyl Chloride3.6 V
Lithium/Sulfuryl Chloride3.9 V
Alkaline1.5 V

Resistance to Shock and Vibration

Spectrum Batteries has cells available in all sizes that are capable of withstanding the high shock and vibration typically encountered in downhole drilling conditions.  For more information on the proper cell selection for applications in these harsh environments, please contact us at
info@spectrumbatteries.com.


Dimensions

Cells available from Spectrum Batteries are optimally sized for downhole tools. Our cell suppliers have developed special sized C, CC, and DD cells to fit in these demanding applications.  The Spectrum Batteries alkaline cell is slightly smaller than most commercially available alkaline cells making it optimally sized for bottom hole pressure surveys

Spectrum Batteries, Inc.* 6910 Sprigg Rd. * Fulshear * TX * 77441

PH: 281.533.9596 * FX: 281.533.9669
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