MDTmag.com 20 / March 2014
for Medical Devices
When developing an electronic medical device, there are many factors that need to be considered. Power is
just one of the critical areas that must be correct and conform to a variety of considerations. This article looks
at battery standards and the design issues most frequently encountered when designing-in batteries.
By Rob Phillips, CEO, Accutronics
Before even starting to talk about bat- tery standards and design pitfalls, it’s worth mentioning that device design
companies usually face an up-front choice as
to whether to appoint an in-house battery
department or turn to independent experts in
the battery field.
Although fundamental battery chemistries
evolve fairly gradually, certain technologies
that sit alongside batteries – such as charger
technology, as well as standards – change
pretty rapidly. “Battery experts” require
constant reskilling in technology and relevant legislation.
As such, it’s usually only large companies, or companies with an extremely rapid
turnover of new device designs, that can
afford to employ in-house battery experts.
Businesses frequently choose to rely on the
expertise of external battery design companies who have a more up-to-date working
knowledge of the battery and charger standards and design issues.
Medical Device Safety Standards
Testing a new medical device (including batteries and chargers) in abnormal or abusive
operation circumstances is a principal safety
requirement. However, complying with
safety regulations is not a guarantee that the
product will continue to operate under such
abnormal conditions, but, instead, simply that
it will not cause injury or damage to personnel or property.
It is also required that the fundamental
safety components, such as cells or fuses,
have been certified to their individual applica-
ble standards. Otherwise, certification is likely
to take longer, frequently resulting in a need
for additional qualification.
The type of product, the intended use of
the product, the market that the product
is sold into, and the timing of the product
placement are the key factors that determine
which standards need to be considered when
designing for medical devices.
Despite geographically unified standards,
many countries still recognize only their own
local standards. This is something worth
consulting if planning to introduce a product
to a foreign market.
Battery Safety Standards
Both high performance lithium ion (Li-ion)
or nickel metal hydride cell (NiMH) batteries
present potential safety challenges. As a
result, there is an extensive debate on standards with regard to qualifying batteries in
medical devices. It is therefore of the utmost
importance to stay informed and choose the
ones that are most relevant to designing-in a
battery for a medical device.
IEC 62133 is the principle battery safety
standard with regard to “Secondary cells
and batteries containing alkaline or other
non-acid electrolytes – Safety requirements
for portable sealed secondary cells”. The
North American equivalent is UL 2054
“Household and Commercial Batteries,”
An example of a custom designed battery and charger, kept separately from the main device