This battery is ideal for such long-term applications as power for electronic devices and electric power, water, and gas meters, and especially as a backup power source for memory ICs.


High 3.6-V voltage
The lithium thionyl chloride battery achieves a high voltage of 3.6 V.

Flat discharge characteristics
The change of internal resistance during discharge is minimal, allowing for flat discharge voltage until end of discharge life.

High energy density
Provides high energy density of 970m Wh/cm3 with discharge current of 100 µA (ER6 type).

Wide usable temperature range
Can be used over a wide temperature range : - 55 deg. C to +85 deg. C (please consult with Maxell, if using in temperatures of -40 deg. C or less).

Superior long-term reliability
The extremely low self-discharge, together with the use of a hermetic seal, allows for stable use over long periods.


Principle and Reactions

The lithium thionyl chloride battery uses liquid thionyl chloride (SOCL2) as its positive active material, and lithium (Li) as its negative active material. The reactions of the battery are shown below.

Battery Reactions
Positive reaction : 2SOCl2+4Li++4e- → 4LiCl+S+SO2
Negative reaction : Li → Li++e-
Total reaction : 2SOCl2+4Li → 4LiCl+S+SO2

Minimum Transient Voltage

The lithium thionyl chloride battery has remarkably lower self-discharge when compared with conventional batteries. This is because a lithium chloride membrane is formed over the negative lithium surface, blocking reaction with the positive material. When first discharging after storage, resistance from this lithium chloride membrane may temporarily reduce the voltage at the initiation of discharge. The lowest voltage at this time is called minimum transient voltage, and the lower the temperature, and the larger the discharge current, the lower the voltage will be. Because minimum transient voltage is greatly influenced by storage time and conditions, it is necessary to take this into sufficient consideration when designing a device.

The figure above shows minimum transient voltage using a fresh battery.

Relationship between Discharge Load and Operating Voltage

The operating voltage of a battery falls as the discharge load increases and temperature falls. In the case of initial use, an electric potential of at least 3 V will be maintained even at temperatures of -40 deg. C at discharge of less than 1 mA.

Storage Characteristics

The lithium thionyl chloride battery is made from chemically stable inorganic materials. Additionally, a sealing method employing a laser-welded seal structure and hermetic seal hinders the admittance of outside air. These features provide superior storage characteristics, holding down self-discharge to no more than 1% of capacity per year at normal temperatures.


  • -OA Machines (Fax, Copiers, Printers)
  • -Desktop PCs
  • -PDAs
  • -Medical Instruments, Cash Registers
  • -FA Instruments (Measuring Instruments, Onboard Microcomputers, Sensors)
  • -Electronic Meters (Gas, Water, Electricity)
  • -ETC (Electronic Toll Collection System)


ModelNominal Voltage (V)Nominal Capacity (mAh)*2Nominal Discharge Current (µA)Operating
(deg. C)
Dimensions*1Weight (g)*1Data SheetsWith
Diameter (mm)Height (mm)
ER18/50 3.6 3,650 125 -55 to +85 18 52.6 22 pdf pdf pdf
ER17/50 3.6 2,750 125 17 52.6 20 pdf pdf
ER6 3.6 2,000 100 14.5 53.5 15 pdf pdf
ER6C 3.6 1,800 100 14.5 51 15 pdf pdf
ER17/33 3.6 1,600 75 17 35 13 pdf pdf
ER3 3.6 1,100 40 14.5 29.9 8 pdf pdf
ER3S 3.6 790 35 14.5 26 7 pdf pdf

*1 Dimensions and weight are for the battery itself, but may vary depending on the shape of terminals or other factors.

*2 Nominal capacity indicates duration until the voltage drops down to 3.0V when discharged at a nominal discharge current at 20 deg. C.

UL Recognized Components

The lithium thionyl chloride battery is a UL (Underwriters Laboratories Inc.) recognized component. (Technician replaceable)

Recognized models: ER18/50, ER17/50, ER6, ER6C, ER17/33, ER3, ER3S
Certification number: MH12568

About Maxell ER batteries

Maxell ER (lithium thionyl chloride) batteries are available only for quipment manufacturers as a built-in part. Therefore, Maxell does not supply these batteries for replacement directly to users of equipment with these batteries. When built-in ER batteries need to be replaced, please contact your equipment manufacturer. If you are planning to use Maxell ER batteries in your equipment as a built-in part, please contact Maxell.

Maxell ER batteries are not general use products. Improper usage may cause not only poor performance but it may also damage the equipment and/or the human body. Therefore, Maxell sells ER batteries only after confirmation of the usage conditions and scope of warranty within the specifications sheet. Maxell does not guarantee the performance and quality of batteries purchased without agreement of the specifications sheet.

Counterfeit batteries on which illegally bearing our trademark "maxell" are offered in the market. Please do not purchase or use such unauthorized batteries for replacement or any other purposes.

-Data and dimensions are not guaranteed. For further details, please contact us at your nearest Maxell office.

-Contents on this website are subject to change without notice.

[Glossary of Battery Terms] : Internal short circuit
[Glossary of Battery Terms] : Short circuit current
[Glossary of Battery Terms] : Leakage resistance
[Glossary of Battery Terms] : Utilization factor
[Glossary of Battery Terms] : Electrolyte
[Glossary of Battery Terms] : Active material
[Glossary of Battery Terms] : Expiry date
[Glossary of Battery Terms] : Aging
[Glossary of Battery Terms] : Test after storage
[Glossary of Battery Terms] : Storage
[Glossary of Battery Terms] : Initial test
[Glossary of Battery Terms] : Energy Density
[Glossary of Battery Terms] : Capacity
[Glossary of Battery Terms] : Duration time (Duration period)
[Glossary of Battery Terms] : Polarization
[Glossary of Battery Terms] : Charge
[Glossary of Battery Terms] : Discharge characteristics (Discharge curve)
[Glossary of Battery Terms] : Self discharge
[Glossary of Battery Terms] : Over discharge
[Glossary of Battery Terms] : Discharge
[Glossary of Battery Terms] : Internal resistance
[Glossary of Battery Terms] : End-point voltage (End voltage, Cutoff voltage, Final voltage)
[Glossary of Battery Terms] : Load
[Glossary of Battery Terms] : Nominal voltage
[Glossary of Battery Terms] : Closed circuit voltage (CCV)
[Glossary of Battery Terms] : Open circuit voltage (OCV)
[Glossary of Battery Terms] : Rechargeable battery (Secondary battery)
[Glossary of Battery Terms] : Primary battery

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