Careful due diligence is required throughout the vendor
selection process, as claims of exceptionally long battery life need to be validated based upon the size of the
battery, its method of construction, as well as environmental considerations. Start by demanding full product
traceability all the way back to the raw materials, as well
as fully documented and verifiable test results for battery
pulses, low-temperature pulses, discharge, and repeatability. To ensure that your remote wireless device is robust
and reliable, select a primary lithium battery that has been
field-proven to deliver long-term performance in harsh
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battery discharge. This phenomenon, known as transient
minimum voltage (TMV), affects bobbin-type LiSOCL2 batteries due to their low-rate design.
One alternative is to create a hybrid lithium thionyl chloride battery that combines a standard long-life bobbin-type
LiSOCL2 cell with a patented hybrid layer capacitor (HLC).
The battery and HLC work in parallel, with the battery
supplying long-term, low-current power, while the HLC
supplies pulses up to 15 A, thus eliminating the voltage drop
that normally occurs when a pulsed load is initially drawn.
The single-unit HLC works in the 3. 6 to 3. 9 V nominal range
to eliminate TMV and deliver high pulses while avoiding the
balancing problems, current leakage, and bulkiness associated with supercapacitors.
If the application requires low to moderate pulses, a
cost-effective solution may be to use an LiSOCL2 cell that
has been specially modified without the use of an HLC to
virtually eliminate the TMV and power delay issues common
to standard LiSOCL2 cells. These modified LiSOCL2 batteries
operate very efficiently and can extend battery operating
life up to 15 percent for certain applications involving extreme temperatures.
All batteries are not created equal
When designing a wireless device for use in a harsh environment, avoid batteries made with inferior raw materials
or sub-standard manufacturing processes, as they can be
prone to electrolyte leakage, short circuits, and reduced
service life. For instance, the annual self-discharge rate of
a leading brand of LiSOCL2battery can be less than 1 percent per year, enabling 40-year operating life, while a lesser quality LiSOCL2 battery may deliver an annual self-discharge of 2. 5 percent to 3 percent per year, which, over
Will “wearables” be the next big thing?
By Bradd Johnson, Torex USA
Consumers don’t like to change batteries or stop to recharge a
device. This is no big revelation to design engineers, who try to
eke out as much life as possible from a battery. There are tradeoffs to consider, however; for example a step-down DC/DC converter is very efficient and provides much longer battery life, but
it typically is more expensive than an LDO voltage regulator, and
the DC/DC converter requires more external components. The
ingenious engineers at Torex designed their XCL series of DC/DC
converters to include an integrated inductor, and this part family
only requires two external capacitors. For design engineers, this
is something which deserves a standing ovation.
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