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Maxim > Design Support > Technical Documents > Application Notes > Battery Management > APP 5070
Keywords: battery management system, lithium ion, temperature measurement, multiplexer, data
acquisition
APPLICATION NOTE 5070
Measure Multiple Temperatures in Battery-
Management Systems, and Save Power Too
By: Kishore Racherla
Feb 07, 2012
Abstract: It is critically important that lithium-ion battery stacks have a good battery-management system
for monitoring many cell voltages and cell temperatures. Without that monitoring, thermal runaway can
lead to a battery explosion. This design idea presents a low-power circuit that measures the temperature
of up to 12 thermistors. It powers and configures the multiplexers, and also puts the muxes into shutdown
to save power when not measuring temperatures.
A similar version of this article was published in Electronic Design on October 6, 2011.
High-voltage, multicell, series-stacked batteries are found in electric vehicles, hybrid electric vehicles,
electric bikes, power tools, and many other devices. Because of their high energy density, lithium-ion
batteries are popular for these applications. It is critically important that these high-energy battery stacks
have a good battery-management system for monitoring the many cell voltages and cell temperatures.
Without that monitoring, thermal runaway can lead to a battery explosion.
Current data-acquisition ICs for battery packs measure multiple cell voltages (typically 12), but they only
scan and measure two temperatures at most. This design idea presents a low-power circuit that
measures the temperature of up to 12 thermistors. It powers the multiplexers and puts the muxes into
shutdown to save power when not measuring temperatures.
The low-power circuit of Figure 1 scans and measures the temperature of all cells in the battery. The
two MAX382 multiplexers switch 12 thermistors to the two auxiliary inputs of a data-acquisition IC (like
the MAX11068 or MAX17830), two thermistors at a time in six pairs. The data-acquisition IC provides
bias for the thermistors, while powering the multiplexers and controlling their switching and
enable/disable functions.
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