title: Measuring electrical properties of batteries at ultra-long timescales

authors: Wilson, Marcus T.

abstract: Quantifying battery behavior is critical to development of new battery technologies and energy storage systems. While it is straightforward to measure properties such as impedance at short timescales (i.e. frequencies larger than ~1 Hz) the relevance of this is questionable since rechargeable batteries in normal usage are often cycled on timescales of hours or days. Making measurements at these timescales, for example impedance measurements below ~1 mHz, is more challenging. In this paper we discuss approaches to quantifying battery behavior at timescales from hours to weeks (frequency scales of ~0.1 mHz down to ~1 μHz). We present frequency domain measurements and time domain measurements, achieved through four-point measurements with a Keysight 66332A at around 100 mA RMS. At low frequencies significant charge is shifted in a measurement cycle, complicating interpretation. The digitization of a sine-wave may introduce errors such as constant current offsets that build in significance with time. The operating point (DC voltage level) of the battery should be controlled since it influences impedance at the lowest frequencies as a result of the voltage-dependent nature of different electrochemical processes. We relate the voltage-dependent effects to time-domain measurements such as cyclic voltammetry and incremental capacity analysis.

text: Measuring electrical properties of batteries at ultra-long timescales Quantifying battery behavior is critical to development of new battery technologies and energy storage systems. While it is straightforward to measure properties such as impedance at short timescales (i.e. frequencies larger than ~1 Hz) the relevance of this is questionable since rechargeable batteries in normal usage are often cycled on timescales of hours or days. Making measurements at these timescales, for example impedance measurements below ~1 mHz, is more challenging. In this paper we discuss approaches to quantifying battery behavior at timescales from hours to weeks (frequency scales of ~0.1 mHz down to ~1 μHz). We present frequency domain measurements and time domain measurements, achieved through four-point measurements with a Keysight 66332A at around 100 mA RMS. At low frequencies significant charge is shifted in a measurement cycle, complicating interpretation. The digitization of a sine-wave may introduce errors such as constant current offsets that build in significance with time. The operating point (DC voltage level) of the battery should be controlled since it influences impedance at the lowest frequencies as a result of the voltage-dependent nature of different electrochemical processes. We relate the voltage-dependent effects to time-domain measurements such as cyclic voltammetry and incremental capacity analysis.

year: 2023

title: National Standards 2016: Retrospective insights, continuing uncertainties and new questions

authors: Thrupp, Martin

subjects: national standards

abstract: New Zealand’s National Standards policy has been deeply controversial in the education sector, especially amongst primary teachers and principals. This article provides a view of the National Standards from their introduction up until 2016, nearly a decade after they were first mooted. The issues covered: (i) offer retrospective insights, (ii) acknowledge continuing uncertainties, or (iii) ask questions that had become newly relevant by 2016. They include processes within the Ministry of Education, the role of advisory groups, the public release of National Standards data, and the origins and impact of the National Standards. They also include whether teachers and principals have been gradually won over to the National Standards, use of the National Standards in ‘social investment’, the Progress and Consistency Tool and possible wider political purposes of headline policies like the National Standards. A theme that connects the issues is concern about policy processes. The article concludes by calling for a more genuine commitment by Government to evidence-informed policy.

text: National Standards 2016: Retrospective insights, continuing uncertainties and new questions New Zealand’s National Standards policy has been deeply controversial in the education sector, especially amongst primary teachers and principals. This article provides a view of the National Standards from their introduction up until 2016, nearly a decade after they were first mooted. The issues covered: (i) offer retrospective insights, (ii) acknowledge continuing uncertainties, or (iii) ask questions that had become newly relevant by 2016. They include processes within the Ministry of Education, the role of advisory groups, the public release of National Standards data, and the origins and impact of the National Standards. They also include whether teachers and principals have been gradually won over to the National Standards, use of the National Standards in ‘social investment’, the Progress and Consistency Tool and possible wider political purposes of headline policies like the National Standards. A theme that connects the issues is concern about policy processes. The article concludes by calling for a more genuine commitment by Government to evidence-informed policy.

year: 2017

title: The timing of the human discovery and colonization of New Zealand

authors: Sutton, Douglas G.

abstract: In discriminating between the proposed Long, Short and Intermediate Chronologies for New Zealand prehistory, archaeologists have recently voted by a narrow majority that the human commensal, Rattus exulans, was present in New Zealand up to 2000 years BP, although the preferred date of ‘first settlement’ by people was ca 800 years BP. A recalibration of New Zealand chronometric data has resulted in reinterpretations of the date and duration of occupation on critical archaeological sites. A remodelling of the ages of the putatively earliest sites in New Zealand has shown these to indicate only a broadly defined period when settlement occurred rather than the date when New Zealand was discovered (as the Short Chronology advocates have insisted). Finally, comparisons with archaeological research on islands elsewhere in the world have brought with them recognition that the discovery, exploration, initial settlement and colonization of New Zealand by Polynesian voyagers were broadly consecutive processes. This paper reviews a range of current evidence in the context of its current theorization and affirms the Long Chronology, recognizing it as the most plausible hypothesis.

text: The timing of the human discovery and colonization of New Zealand In discriminating between the proposed Long, Short and Intermediate Chronologies for New Zealand prehistory, archaeologists have recently voted by a narrow majority that the human commensal, Rattus exulans, was present in New Zealand up to 2000 years BP, although the preferred date of ‘first settlement’ by people was ca 800 years BP. A recalibration of New Zealand chronometric data has resulted in reinterpretations of the date and duration of occupation on critical archaeological sites. A remodelling of the ages of the putatively earliest sites in New Zealand has shown these to indicate only a broadly defined period when settlement occurred rather than the date when New Zealand was discovered (as the Short Chronology advocates have insisted). Finally, comparisons with archaeological research on islands elsewhere in the world have brought with them recognition that the discovery, exploration, initial settlement and colonization of New Zealand by Polynesian voyagers were broadly consecutive processes. This paper reviews a range of current evidence in the context of its current theorization and affirms the Long Chronology, recognizing it as the most plausible hypothesis.

year: 2008