Intra-Module Isolation Devices for High Voltage Energy Storage - Part II and Further Energy Storage Analysis
Abstract
Task 1: Development of an instrumented ~100V lithium-ion battery It is proposed that initially we will develop a high voltage, 114V lithium-ion battery constructed in the form of 38 V, 10S/1P lithium-ion battery modules. It is proposed here that Saft VL30PFe-A cells be used in the proposed work. These cells have been previously validated at current rates as high as 400 A and are being considered already for other Naval energy storage systems. The modules will be interconnected via voltage controlled, mechanical, 500 A relays. We will start out at lower voltage, ~114 V, in order to ensure that the control system that is developed can be validated at safer operational levels. An I+Me battery management system which utilizes high current balancing boards will be used and the voltages measured by it will be fed to the control system just as it will be in a fielded Navy battery system. Custom developed differential voltage measurement boards will be used as a redundant voltage measurement across each individual cell. The temperature of each cell will also be monitored and recoded using NI 9213 thermal monitoring equipment. It is proposed that these properties be studied so that techniques to mitigate any possible problems this brings can be properly managed, especially as the battery is transitioned to lithium-ion batteries with higher stored energies and potential danger. Task 2: Development of an active control system Using NI data acquisition systems already in house at UTA, a control system will be developed to read in and monitor all of the voltage, current, and temperature data discussed earlier. In order to evaluate 6 fault isolation techniques, faults must be induced or simulated in the control system. It is proposed that the latter be employed. Within the control system, the operator will be able to manipulate the current, voltage, or temperature data read by the control system. Task 3: Development of an instrumented ~1000 V lithium-ion battery As previously indicated, the plan is to work our way up in voltage. The battery will be constructed of 26 – 10S/1P modules which are all constructed in water flow only cold plates manufactured by ThermAvant LLC. The cold plates will ensure the batteries are cooled to a safe level when they are operated at current rates as high as 500 A. TE Connectivity LEV200A5NAA relays will be procured to use in series with each module. Additionally, some relays may be connected across modules so that the battery can remain operational in the event only one or two modules fails as the DC/DC converter will still operate properly if the number of modules that drop out are not too high in count. Task 4. Characterization of the parallel connection of multiple LIB Batteries There are multiple ways to connect up lithium-ion batteries in parallel in order to achieve higher overall capacity. One method is to connect individual strings of batteries in series and then connect multiple stings in parallel connecting only the two end terminals. Using this method, a BMS is typically used to balance each cell and no other protection is needed. The other method is simply to connect multiple single cells in series and then connect up the parallel modules in series. This reduces the overall complexity of the system and the number of BMS systems needed however, there is no provision to balance each cell, which may have very different ESRs, since there is no isolation between the parallel cells. This means that cells of various ESRs may discharge currents at different rates and accept currents at different rates when it is intended for them to share current equally. This will cause cells to heat up at different rates and also to age at different rates. In order to understand to what extent current sharing is unequal given a certain variation in ESRs, a study is proposed to understand and characterize this phenomena.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512178
Entities
People
- David A. Wetz
Organizations
- Office of Naval Research
- United States Navy
- University of Texas at Arlington