grade-lithium metal oxide batteries are
often a good choice.
Lithium metal oxide batteries can
deliver high voltage and high energy
density, along with instant activation and
extended operating life, even at extreme
temperatures. Lithium oxide batteries
deliver an open circuit voltage of 4.0 V
with high pulses of up to 15 A and 5 A
continuous current at 3. 2 V (see Table 2),
enabling hand-held medical devices to
become lighter and more miniaturized.
For example, the BioAccess portable
small bone drill (Figure 1) was originally
powered by an alkaline battery pack that
performed well and offered excellent reli-
ability. By substituting 6 AA-size TLM-
1550HP lithium metal oxide batteries
for the alkaline battery pack, BioAccess
achieved a 64 percent weight reduction
and a 60 percent volume reduction. An
equivalent alkaline battery pack would
have required 3X the weight and 2. 5 times
the volume ( 15 AA-size alkaline batteries
vs. 6 AA-size TLM-1550-HP batteries).
Use of a lithium metal oxide battery
pack also enabled the BioAccess surgical
drill to deliver faster drilling speeds, more
active drill time ( 30 to 40 seconds at a
time for up to 20 to 30 cycles), more
instantaneous power, and greater stall
torque, resulting in more efficient drilling
cycles with less operator fatigue.
4. Sterilized or frozen?
Alkaline batteries utilize a water-based
chemistry that is unsuited for use at ex-
treme temperatures. Due to the absence
of water and the chemical and physical
stability of the electrolyte materials, bob-
bin-type LiSOCl2 batteries are unique
in their ability to withstand extreme
temperatures (see Table 2).
Bobbin-type LiSOCl2 batteries
(Figure 2) are utilized in Awarepoint
radio frequency identification (RFID)
real time location systems (RTLS) that
continually monitor the location and status of medical equipment. Environmental
tests performed by Awarepoint showed
that the bobbin-type LiSOCl2 batteries
could withstand +135°C temperatures
and could work continuously for 500
steam sterilization cycles without having
to remove the battery prior to sterilization. The battery is rated for a 0.55 Ah
capacity 0.5 mA, while also being
completely safe, UL recognized, and
non-hazardous when shipped.
Specially modified bobbin-type
LiSOCl2 batteries are also utilized in
the medical cold chain, where frozen
tissue samples, transplant organs, medical
supplies, and pharmaceuticals need to be
continually monitored during shipment
at -80°C, far beyond the performance
capabilities of consumer-grade batteries.
5. Does the device need to have an
extended shelf life?
Bobbin-type LiSOCl2 batteries are
also ideal for medical applications that
consume low average daily current and
require extended battery life of up to 40
years due to a very low self-discharge
rate of less than 1 percent per year.
These applications include bone healers,
oxygen meters, and glucose meters.
A superior quality bobbin-type
LiSOCl2 cell can feature an average
annual self-discharge rate of 0.7 percent,
whereas a lesser quality LiSOCl2 battery
can have an annual self-discharge rate of
up to 3.0 percent per year. Such extended
shelf life can be important for applications such as automatic external defibrillators (AEDs), that often remain idle for
years but then need to perform reliably
in a life-saving emergency.
Industrial-grade lithium metal oxide
and rechargeable Li-ion batteries can
also deliver very long shelf life, making
them suitable for use in AEDs and other
medical devices that require very long
6. Does the device need to
As the Io T and the IIoT expand, there
will be growing demand for wireless
medical devices that can ‘connected’ via
two-way wireless communications.
If the medical device requires
a long-life primary battery, and is
intended for very long operating life
by drawing low average daily current,
then various methods can be used
to conserve energy, including: the
use of a low power communication
protocol (i.e. ZigBee, Wireless HART,
LoRa, etc.); intelligent circuit design
using low power microprocessors and
components; programming the device
to remain mainly in a ‘stand-by’ mode,
awakening only at pre-programmed
intervals or during periodic data
queries; and by reducing energy consumed during ‘active’ modes of data
interrogation and transmission.
Standard bobbin-type LiSOCl2
batteries can be modified to deliver high
pulses through the addition of a hybrid
layer capacitor (HLC) that acts like a
rechargeable battery to store high pulses.
Applications that draw higher amounts
of average daily current could require the
use of an industrial grade Li-ion battery or a supercapacitor to deliver high
Looking to the future
‘Big Data’ and AI are transforming modern medicine, making battery-operated
medical devices increasingly essential to
the healthcare delivery system. Wireless connectivity will be enhanced by
wearable devices and other technologies
that deliver real-time data to healthcare practitioners to help improve the
quality, immediacy, and predictability
of patient care. This trend will spur
growing demand for industrial-grade
batteries that can deliver relatively high
current pulses. MDT
Figure 2. Bobbin-type LiSOCl2 batteries are
commonly used in bone growth stimulators
and AEDs, and can handle the extreme
temperatures (-80°C to 125°C) of the medical cold chain and autoclave sterilization.