Objectives
Provide DOE, USABC, and battery developers with reliable, independent and unbiased performance evaluations of cells, modules and battery packs.
Benchmark battery technologies which were not developed with DOE/USABC funding to ascertain their level of maturity.
Technical Barriers
This project addresses the following technical barriers as described in the USABC goals [1, 2, and 3]: (A) Performance at ambient and sub-ambient
temperatures.
(B) Calendar and cycle life.
Technical Targets
PHEV Technical Targets 15-year calendar life. 5,000 CD cycles.
Other technical targets exist for EV, HEV and LEESS applications
Accomplishments
Tested battery deliverables from many developers: HEV and LEESS batteries: Test contract
deliverables from A123 Systems (in progress) and Leyden Energy (in progress).
PHEV batteries: Test contract deliverables from Johnson Controls, Incorporated (in progress) and A123 (in progress).
EV batteries: Seeo (complete), Optodot (in progress), 3M (in progress) and DowKokam (in progress).
Benchmark battery technologies for vehicle applications. Test deliverables from Cobasys (in progress), SK Energy (in progress), ActaCell (in progress) and DowKokam (EV; complete).
Compare EV battery test protocols used in the U.S. and in China (Argonne lead; in progress).
Introduction
Batteries are evaluated using standard tests and protocols which are transparent to technology. Two protocol sets are used: one that was developed by the USABC [1, 2], and another which provides a rapid screening of the technology. The discussion below focuses on results obtained using these standard protocols.
Approach
The batteries are evaluated using standardized and unbiased protocols, allowing a direct comparison of performance within a technology and across technologies. For those tested using the USABC methods, the performance of small cells can be compared to that of larger cells and full-sized pack by means of a battery scaling factor [1, 2].
Results
Independently, organizations in the U.S. and China have developed battery testing protocols. Even though these protocols started from the same basic
understanding of electrochemistry, the protocols that each country uses reflect differences in philosophy and approach.
In the U.S., ANL and INL and in China, CATARC are collaborating to compare battery testing procedures and methods. The collaboration may establish
Bloom – ANL IV.B.1 Battery Performance and Life Testing
standardized, accelerated test procedures and will allow battery testing organizations to cooperate in the analysis of the resulting data. In turn, the collaboration may accelerate electric vehicle development and deployment. The three steps and progress in this collaborative effort are shown in Table IV - 3.
Table IV - 3. Steps and progress in the collaborative testing effort
Step Status
Collect and discuss battery test protocols from various organizations/countries
Complete
Conduct side-by-side tests using all protocols
for a given application, such as an EV In progress Compare the results, noting similarities and
differences between protocols and test sites
In progress
Initially, the approach to testing was different. The USABC tests focus on pre-competitive experiments using an ideal, family-sized car. In contrast, those from China were centered on how the battery performed in a given automobile.
The tests focused on the EV application. Here, the USABC protocol consisted of a dynamic, constant- power discharge and constant-current charging. The
Chinese protocol consisted of constant-current discharges (C/3 rate) and charges. USABC reference performance test (RPT) consisted of two C/3 capacity cycles, a peak power pulse test at 10% DOD increments and full DST cycle. The cells were characterized using these tests every 50 cycles. In contrast, the Chinese RPT consisted of one C/3 capacity cycle and 10 second discharge pulse at 50% DOD. The RPT is performed every 25 cycles. Both cycle-life protocols terminate discharge at 80% DOD.
The tests were performed using commercially- available cells containing LiFePO4- and graphite-based chemistry. Figure IV - 31 shows the trend in specific power obtained using the Chinese test protocol and measured at ANL and INL. The figure shows that the specific power of the battery decreased with cycling and that the measurements and trends obtained at the two labs were very similar.
Figure IV - 32 shows the change in average, relative capacity using the two test protocols, USABC and Chinese. From the figure, the Chinese protocol produced more capacity fade than the USABC at ANL; there was no significant difference between the protocols at INL; and, at CATARC, the result indicate that the capacity faded more using the Chinese protocol than the USABC. Some of these differences may be due to lot and cell-to-cell variation. Investigation into these differences is still in progress.
IV.B.1 Battery Performance and Life Testing Bloom – ANL
Figure IV - 32: Change in average, relative capacity measured using the two test protocols at the three test sites
Conclusions and Future Directions
Testing has been shown to be a useful way to gauge the state of a developer’s technology and to estimate the life of a battery.
For the future, we plan to:
Continue testing HEV contract deliverables. Continue testing PHEV contract deliverables. Continue testing EV contract deliverables. Begin testing LEESS contract deliverables. Continue acquiring and benchmarking
batteries from non-DOE sources.
Aid in refining standardized test protocols. Upgrade and expand test capabilities to handle
increase in deliverables.
Continue the protocol comparison. Explore other possibilities for test protocol
comparison and, perhaps, standardization with Europe, Japan and China.