ams introduces cost-saving system management reference design for lithium pedelec/e-bike batteries
March 17 2014 - 3:00AM
Business Wire
Blueprint for controllerless balancing and voltage monitoring
shows how to reduce component count and BoM cost while providing
essential safety functions
ams AG (SIX:AMS), a leading provider of high performance analog
ICs and sensors, today introduced an example design for lithium
pedelec/e-bike batteries which implements accurate cell monitoring
and balancing without the need for a microcontroller in the Battery
Management System (BMS).
Battery pack and pedelec manufacturers which use the design will
benefit from valuable bill-of-materials (BoM) cost savings and a
simpler circuit design, compared to batteries in production
today.
The ams design is for a 48V pedelec battery consisting of up to
14 lithium-ion cells. It uses two AS8506 smart cell monitoring ICs,
with few supporting components, to monitor the temperature and
voltage of up to seven cells each and to implement passive
balancing of the cells when charging.
By contrast, conventional BMS designs in pedelecs use dumb
voltage monitoring ICs to measure the voltage and temperature of
cells, reporting the values to a dedicated battery management
microcontroller via a serial communications link. The MCU is
required to control safety and protection functions (over- and
under-voltage and over-temperature shut-down) and cell
balancing.
The AS8506 from ams, however, includes built-in logic functions
for controlling cell safety, protection and balancing. These
functions can easily be configured by the user, with the settings
saved in an on-board OTP memory. The device also features
integrated MOSFETs for use in passive cell balancing operations.
During charging, each cell’s voltage is compared to a
user-programmable reference voltage threshold. Up to 100mA may be
discharged through the MOSFET from any cell exceeding the
threshold, until all cells have reached the threshold and the
battery module is fully charged.
This architecture, in which battery monitoring and cell
balancing operations are implemented inside the AS8506
voltage-monitoring device, dispenses with the dedicated MCU
required in conventional pedelec battery designs. When an AS8506
detects an over- or under-voltage or over-temperature condition, an
interrupt signal is transmitted to the pedelec’s motor controller
IC to complete the required safety shut-down operations.
‘Battery lifetime, safety and run-time strongly affect
consumers’ choice of pedelec, but so does cost,’ said Bernd
Gessner, Vice President and General Manager of the automotive
business unit of ams. ‘The controllerless reference design from ams
helps pedelec manufacturers meet consumer demand by providing
outstanding safety and battery performance, but in a simpler and
lower-cost architecture than has previously been available.’
The reference design can be used in any pedelec or e-bike
battery containing up to 14 lithium-ion cells. It can also be
extended to supervise more than 14 cells by daisy-chaining
additional AS8506 ICs as required.
The reference design files are available on request from
ams.
Price & Availability
The AS8506 cell monitoring IC is in volume production now. It is
priced at $9.10 for 1,000 pieces.
Technical Support
Demo kits for the AS8506 are available online from ams. For
further information on the AS8506 demo kit or to request samples,
please visit www.ams.com/battery-stack-monitor/AS8506-demokit.
Download Press Picture or Block Diagram of this IC at
http://www.ams.com/eng/Press/Press-Releases/AS8506_refdesign
ams AGPatricia Moosburger, Media Relationsphone: +43 (0) 3136
500 31235press@ams.comwww.ams.com
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