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State of charge and state of health estimation for lithium iron phosphate batteries
Thesis (MEng)--Stellenbosch University, 2023.
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| Format: | Thesis |
| Language: | en_ZA en_ZA |
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Stellenbosch : Stellenbosch University
2023
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| _version_ | 1867613957703860224 |
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| access_status_str | Open Access |
| author | Snyman, Ricket |
| author2 | Strauss, Johann |
| author_browse | Snyman, Ricket Strauss, Johann |
| author_facet | Strauss, Johann Snyman, Ricket |
| author_sort | Snyman, Ricket |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng)--Stellenbosch University, 2023. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/127309 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA en_ZA |
| last_indexed | 2026-06-10T12:44:24.378Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2023 |
| publishDateRange | 2023 |
| publishDateSort | 2023 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/127309 State of charge and state of health estimation for lithium iron phosphate batteries Snyman, Ricket Strauss, Johann Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. Lithium cells Energy storage Estimation theory Thesis (MEng)--Stellenbosch University, 2023. ENGLISH ABSTRACT: Accurate state of charge (SOC) and state of health (SOH) is important for safe and optimal operation of lithium batteries. This study investigates multiple existing SOC and SOH estimation methods. These methods are analyzed for their advantages and disad- vantages. There is speci_cally focused on the practicality of these methods to implement them in a typical energy storage system with variable operating conditions. The relationship between the saturation charged energy (energy that is charged dur- ing the saturation charge phase) and the SOH of a lithium iron phosphate (LFP) cell is investigated. A SOH estimation method is proposed based on this relationship that is found. This estimation method only requires partial charging data and does not need data of a full charge or discharge cycle. A hardware system is developed to perform charge and discharge cycles on a single LFP cell while monitoring the vital parameters of the cell. This system is used to perform all testing that is required to develop and evaluate the proposed SOH estimation method. The coulomb counting SOC estimation method is investigated to be improved. Various enhancements are made to the existing method to increase its accuracy and practicality. There is speci_cally focused on considering the charge and discharge e_ciencies of a LFP cell while performing coulomb counting. The OCV (open-circuit voltage) SOC estima- tion method is also combined with the coulomb counting method to form a hybrid SOC estimation method. It was found that the improved hybrid SOC estimation method and the newly found SOH estimation method showed similar accuracy when compared to existing methods. But the main bene_t of these new found methods is their practicality for typical LFP energy storage systems. The improved methods proved to be insensitive to their operating conditions as they do not require a very controlled charge or discharge cycle to obtain accurate estimation values for the SOC and SOH. AFRIKAANS OPSOMMING: Akkurate laaitoestand (LT Eng:SOC) en gesondheidstoestand (GT Eng:SOH) is be-langrik vir veilige en optimale gebruik van litium batterye. Hierdie studie ondersoek verskeie bestaande LT en GT beramingsmetodes. Hierdie metodes word ontleed vir hul voor- en nadele. Daar word spesi ek gefokus op die praktiese toepassing van hierdie metodes om dit in 'n tipiese energiebergingstelsel met veranderlike bedryfstoestande te implementeer. Die verwantskap tussen die energie wat tydens die versadigingsladingfase van 'n LFP- sel gelaai word en die GT van die sel word ondersoek. 'n GT beramingsmetode word voorgestel op grond van hierdie verwantskap wat gevind word. Hierdie beramingsmetode vereis slegs gedeeltelike laai data en benodig nie data van 'n volle laai- of ontlaai-siklus nie. 'n Hardewarestelsel word ontwikkel om laai- en ontlaai-siklusse op 'n enkele litium- ysterfosfaat (LFP)-sel uit te voer terwyl die kritiese parameters van die sel gemonitor word. Hierdie stelsel word gebruik om alle toetse uit te voer wat nodig is om die voorge- stelde GT beramingsmetode te ontwikkel en te evalueer. Die coulomb telling LT beramingsmetode word ondersoek om verbeter te word. Ver- skeie verbeterings word aan die bestaande metode aangebring om die akkuraatheid en bruikbaarheid daarvan te verhoog. Daar is spesi ek gefokus op die oorweging van die laai- en ontlaai doeltre endheid van 'n LFP-sel terwyl coulomb-telling uitgevoer word. Die oop kring spanning LT beramingsmetode word ook gekombineer met die coulomb- telmetode om 'n hibriede SOC-beramingsmetode te vorm. Daar is gevind dat die verbeterde hibriede LT beramingsmetode en die nuutgevonde GT beramingsmetode soortgelyke akkuraatheid getoon het in vergelyking met bestaande metodes. Maar die grootste voordeel van hierdie nuutgevonde metodes is hul praktiese toepassing vir tipiese LFP-energiebergingstelsels. Die verbeterde metodes toon om on- sesitief te wees vir hul bedryfstoestande aangesien dit nie 'n baie beheerde volle laai of ontlaai-siklus benodig om akkurate beramingswaardes vir die LT en GT te verkry nie. Masters 2023-03-07T07:29:48Z 2023-05-18T07:15:20Z 2023-03-07T07:29:48Z 2023-05-18T07:15:20Z 2023-03 Thesis http://hdl.handle.net/10019.1/127309 en_ZA en_ZA Stellenbosch University xv, 104, 11 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Lithium cells Energy storage Estimation theory Snyman, Ricket State of charge and state of health estimation for lithium iron phosphate batteries |
| title | State of charge and state of health estimation for lithium iron phosphate batteries |
| title_full | State of charge and state of health estimation for lithium iron phosphate batteries |
| title_fullStr | State of charge and state of health estimation for lithium iron phosphate batteries |
| title_full_unstemmed | State of charge and state of health estimation for lithium iron phosphate batteries |
| title_short | State of charge and state of health estimation for lithium iron phosphate batteries |
| title_sort | state of charge and state of health estimation for lithium iron phosphate batteries |
| topic | Lithium cells Energy storage Estimation theory |
| url | http://hdl.handle.net/10019.1/127309 |
| work_keys_str_mv | AT snymanricket stateofchargeandstateofhealthestimationforlithiumironphosphatebatteries |