This document discusses using thermoelectric devices (TEDs) for distributed battery thermal management. It proposes integrating TEDs directly into battery bus bars to provide localized and individually controlled cooling of battery cells. Modeling shows TED-only cooling of 5 watts per cell can maintain a 10-year battery life. Future development testing will evaluate air-cooled TED concepts for battery thermal management and utilize a simplified drive cycle generating 3.5-5 watts of heat per cell. Thermoelectric battery thermal management could enable active cooling solutions for mild hybrid applications without liquid cooling loops.

1. Distributed Battery Thermal
Management Using
Thermoelectrics
Author(s): Todd Barnhart1,
Madhav Karri1, Dmitri
Kossakovski1, Alfred Piggott1,
Kandler Smith2
Organization: Gentherm Inc. 1 ,
NREL2
Paper Number: 13TMSS-0006
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2. Overview
 Concept Description
 Proposed Packaging
 Experiment Summary
 Thermal Impact Simulations
 Battery Life Calculations
 Future Development Testing
 BTMS Value
 Summary
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3. Battery Thermal Management via
Thermoelectrics
Approach: localized, individually controlled, distributed thermal
management of individual cells via direct conductor cooling
using thermoelectric devices
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* Patent pending

4. Thermal Gradients in Working Cells
Cell level thermal gradients:
Simulated thermal gradient of discharging cell (Tata Motors, UK)
S. Chacko, Y.M. Chung / Journal of Power Sources 213 (2012) 296-303
Pack level thermal gradients:
Also: .. a 5 K difference across the pack would result in an approximate 25 %
acceleration of the aging kinetics (JCI, EVS24 2009).
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5. Thermoelectrics Can Compensate for Thermal
Gradients
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6. Advantages of Thermoelectrics
 Provide low power active cooling solutions for
start/stop or mild/micro-hybrid battery applications.
 Air cooled TE solutions can provide a “stand-alone”
active cooling system.
•
“Stand-alone” = No liquid or refrigerant loops required.
 Potential enabler to allow under-hood packaging of
Li-ion batteries.
 Precision independent cell cooling, reducing pack
gradient and improving life.
 Light weight and compact packaging.
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7. 30 Watt TE Cooling System
• 12 V Li-ion Battery for
hybrid electrical
system.
• 4 cells - per DIN
SPEC 91252
dimensions for
prismatic cells.
• 10 Watt TED’s
integrated into bus
bars.
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8. Thermoelectric Battery Thermal
Management
• BTMS fully integrated with existing BMS (Battery
Management System).
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9. Assembly details
Integrated Battery Management System (BMS) and
Thermoelectric Management System (TMS)
Integrated TED and bus bar.
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10. Modeling of Benefits of Distributed Thermal
Management – Gentherm/NREL Study
Approach:
-
Simulate a pack of 50 power cells
-
Use existing thermal network models
-
Apply TEDs either to all or selected cells
-
Use typical drive cycles
-
Analyze thermal conditions and predict life
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Lump thermal
network model,
excludes 3D FEA of
cells/pack

11. Simulation Definition
Application: HEV
Battery warranty: 10 years, 150k miles
Cell: 5 Ah (power cell)
Pack: 50 cells
Driving:
US06 cycle (48A RMS current, 8.01 miles/cycle,
48.4 mph average speed)
41.1 miles/day (150k miles, 10 years)
2 driving trips/day (20.5 min ea.), 8 am and 5 pm
Ambient temperature 28°C (e.g. Phoenix average)
Chilled fluid @ 23°C (e.g. via secondary HVAC loop)
Or, conditioned air from cabin
Heat transfer:
•Cooled surface area: 0.0208 m2/cell
•Air ~ 9 W/m2 K
•Liquid ~ 85 W/m2 K
Thermal Management Objectives
used in Simulation:
• Lumped cooling: Maintain pack
average temperature at 25oC
• Distributed cooling: Maintain
individual cell temperatures at
25oC
Thermal Management Modes of
Operation:
• Nominal cooling: Key-on
• Standby cooling: Key-off,
drawing power from either HEV
battery (50 Wh limit) or external
source such as solar panel
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12. Lumped cooling: Cell-to-cell T difference
Low ambient T
High ambient T
Temperature of cell
vs. cell location
T across pack vs. Ambient
temp
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Temperature of cell
vs. cell location

13. Battery Life vs. Control Strategy @ Various
Cooling Power Levels
>10 yr life with TE-only (no chilled air or liquid) cooling becomes feasible
with ~5 W/cell
Notes: The results are specific to pack model, control algorithm and
environmental conditions.
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14. Future Development Testing
 Modeling & Test Plan:
 Evaluate 2 TE based cooling concepts.
 Evaluate 2 air cooled solutions for
baseline comparison.
 Testing to be conducted by NREL.
 Use simplified 48V micro-hybrid cycle.
 Averages 3.5 – 5.0W of heat
generation per cell.
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15. Development Test Configuration
Electrode Tab TE Cooling
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16. Charge/Discharge Cycle
Simplified 48V Drive Cycle
Cycle generates 3.5 – 5.0 Watts of heat
per cell, depending on cell temperature.
Cell Based Cycle
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17. Value of Thermal Management
 The value equation for BTM systems is still TBD for
small pack formats:
 Life targets are still being established; 4, 6, 8 or 10years?
 Replacement cost vs. customer expectations
 Life targets will set thresholds for peak operating temperatures.
 The BMS will limit battery function to avoid exceeding peak
operating temperatures.
 BTM systems value will be in enabling wider operating ranges,
which allows OEM’s more output (FEI) and life from their battery.
TE based BTMS is first being targeted for applications requiring
“Stand-alone” solutions requiring 50-200W of cooling.
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18. Summary
 TE cooling may be well aligned with
start/stop or micro-hybrid battery
applications. Affordable & flexibility of design
options.
 TE’s provide light weight, solid-state,
scalable & “Stand alone” cooling systems.
 Optimized BTM systems add value by
allowing OEMs to drive batteries harder and
still meeting life targets. (Delivers more FEI)
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