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Appendix D – Battery Selection
The following section applies to transmitter modules. Some enclosures will determine the battery type and size.
Considerations When Selecting Batteries
Re-chargeable or replacement
This really depends on the application. Some applications where expected battery life with alkaline batteries will
be many years would probably not warrant the use of re-chargeable batteries. Re-chargeable batteries have
implementation issues such as how to connect to the charger, how to seal this connection if required, can the
batteries be re-charged at a convenient point in the operation of the module i.e. between shifts and does the
voltage, when charging, exceed the maximum supply voltage of the transmitter module if so the inline charging
module will need to be fitted.
Required battery life
Driven by the application and mainly dependent on measurement rate and sample time. The operation would
normally require that the transmitter module is used in Low Power Mode to maximise battery life.
Size of
Choosing a battery will be influenced by how much space is available and what battery life is required, generally
the bigger the battery the longer it will last.
Operating temperature range
A battery's useable capacity is influenced by its operating temperature. Generally, the lower the temperature the
lower their ability to provide charge. Beware of the batteries specified operating range when considering a
particular battery technology.
Self-discharge.
Batteries are chemical devices and have a shelf life which needs to be considered in application where long
battery life is required. Typically an Alkaline has a battery life of 5 years.
Internal Resistance of battery
Low internal resistance is important, the higher the resistance the less useful life of the battery is available. This is
due to voltage drops caused during the high current phase of the measurement cycle. In the case of a T24-SAf
strain gauge input module 300mA required for 250us. Batteries with an internal resistance greater than 150 milli
ohm may require additional capacitor modules to supply the peak current.
Connections to battery
For the same reasons internal resistance must be low it is important to keep any voltage drops from the battery
to the transmitter module as low as possible too. Care must be taken in selecting the connection method
between batteries and transmitter module. For example cables should be kept as short and thick as possible.
If sourcing battery holders for OEM transmitter modules be aware that some holders with springs only on one
side of the battery can temporarily disconnect a battery when subjected to a shock force. This may have the
unexpected effect of resetting or restarting a module. In the case of a transmitter module that is in a deep sleep
mode this may wake the module.
Mantracourt Electronics Limited
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T24 Telemetry User Manual
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