{ "node": { "id": "term:self-discharge-test", "type": "Term", "label": "Self-discharge test", "properties": { "id": "self-discharge-test", "name": "Self-discharge test", "section": "topic-testing", "definition": "Charging a cell to a set state, storing it, and measuring either the OCV drop over days or the capacity lost over weeks. In production it is the K-value check; in the laboratory a potentiostatic hold measures the leakage current directly in hours.", "related": [ "self-discharge", "k-value", "open-circuit-voltage", "internal-short-circuit" ], "url": "https://lemonergy.com/learn/glossary/self-discharge-test/", "mentions": [ "chronoamperometry" ] } }, "edges": [ { "id": "edge:3957", "source": "term:self-discharge-test", "target": "topic:topic-testing", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:3958", "source": "term:self-discharge-test", "target": "term:self-discharge", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:3959", "source": "term:self-discharge-test", "target": "term:k-value", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:3960", "source": "term:self-discharge-test", "target": "term:open-circuit-voltage", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:3961", "source": "term:self-discharge-test", "target": "term:internal-short-circuit", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/self-discharge-test/chronoamperometry", "source": "term:self-discharge-test", "target": "term:chronoamperometry", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:3963", "source": "term:self-discharge-test", "target": "visual:self-discharge", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "neighbors": [ { "id": "topic:topic-testing", "type": "Topic", "label": "Testing methods", "properties": { "id": "topic-testing", "name": "Testing methods", "lede": "The measurements and test procedures that characterise a cell or pack, from capacity and pulse tests to abuse and environmental tests.", "context": "Record specimen, state, instrument, temperature and timing.", "example": "Resistance immediately after a current step can differ from a ten-second value because slower polarization contributes.", "lesson_url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/", "lesson_label": "Open capacity measurements" } }, { "id": "term:self-discharge", "type": "Term", "label": "Self-discharge", "properties": { "id": "self-discharge", "name": "Self-discharge", "section": "topic-charging", "definition": "The slow loss of stored charge while a cell is not in use. An unexpected rise can signal a leakage path or a soft internal short.", "unit": "%/month", "related": [ "internal-short-circuit", "calendar-aging", "k-value", "calendar-life", "self-discharge-test" ], "lesson": "fundamentals/battery-aging/#check-yourself", "url": "https://lemonergy.com/learn/glossary/self-discharge/", "mentions": [] } }, { "id": "term:k-value", "type": "Term", "label": "K-value", "properties": { "id": "k-value", "name": "K-value", "aka": [ "OCV drop rate" ], "section": "topic-manufacturing", "definition": "The rate at which a cell’s open-circuit voltage falls during the production aging step, in millivolts per day. A high K-value signals an internal short or contamination, and such cells are scrapped before shipment.", "unit": "mV/day", "related": [ "aging-step", "self-discharge", "open-circuit-voltage", "internal-short-circuit" ], "url": "https://lemonergy.com/learn/glossary/k-value/", "mentions": [] } }, { "id": "term:open-circuit-voltage", "type": "Term", "label": "Open-circuit voltage", "properties": { "id": "open-circuit-voltage", "name": "Open-circuit voltage", "abbr": "OCV", "section": "topic-state", "definition": "The voltage across a cell’s terminals when no current flows and the cell has rested long enough for the voltage to settle. It depends on state of charge and temperature, and a cell whose open-circuit voltage falls unusually fast in storage may have an internal short.", "unit": "V", "related": [ "ocv-soc-curve", "relaxation", "voltage-hysteresis", "k-value", "internal-short-circuit" ], "lesson": "fundamentals/cell-production/#finishing", "url": "https://lemonergy.com/learn/glossary/open-circuit-voltage/", "mentions": [ "state-of-charge" ] } }, { "id": "term:internal-short-circuit", "type": "Term", "label": "Internal short circuit", "properties": { "id": "internal-short-circuit", "name": "Internal short circuit", "abbr": "ISC", "section": "topic-safety", "definition": "An unintended electronic path between the electrodes inside a cell — through a metal particle, a burr, a damaged separator or lithium deposits. It discharges the cell internally and turns its energy into local heat.", "related": [ "thermal-runaway", "dendrite", "separator", "external-short-circuit", "self-discharge", "internal-short-trigger-device" ], "lesson": "fundamentals/cell-anatomy/#short-circuit", "url": "https://lemonergy.com/learn/glossary/internal-short-circuit/", "mentions": [ "electronic-path", "burr", "metal-particle-contamination" ] } }, { "id": "term:chronoamperometry", "type": "Term", "label": "Chronoamperometry", "properties": { "id": "chronoamperometry", "name": "Chronoamperometry", "aka": [ "potentiostatic hold", "potential step" ], "section": "topic-testing", "definition": "Stepping an electrode to a fixed potential and recording how the current decays with time. A diffusion-limited current falls with the inverse square root of time, the Cottrell relation, which yields diffusion coefficients; long holds measure leakage currents from electrolyte oxidation or self-discharge, and a staircase of small steps is PITT.", "formula": "i(t) = n·F·A·c·√(D / (π·t))", "related": [ "pitt", "potentiostat", "diffusion-coefficient", "self-discharge-test", "chronopotentiometry" ], "example": { "title": "Compare a diffusion-controlled current at two times", "text": "In the ideal Cottrell regime i ∝ 1/√t. If the current is 2 mA at 1 s, the model gives 1 mA at 4 s. This applies only while the assumed planar semi-infinite diffusion and potential-step conditions hold." }, "url": "https://lemonergy.com/learn/glossary/chronoamperometry/", "mentions": [ "electrode", "electrolyte", "self-discharge", "oxidation", "diffusion" ] } }, { "id": "visual:self-discharge", "type": "Visual", "label": "Charge retention during storage", "properties": { "title": "Charge retention during storage", "summary": "A constant fractional loss produces an exponential decline.", "readout": "After 6 months: 83.297% retained; after 12: 69.384%.", "formula": "Q(t)/Q₀ = (1 − monthly loss)^t", "note": "Constant fractional loss; chemistry and temperature effects are not modeled.", "software": { "status": "reference", "label": "Reference concept", "body": "This is an illustrative retention model. battery-core aging functions do not estimate self-discharge. Reversible charge loss differs from permanent capacity fade.", "href": "../fundamentals/battery-aging/" }, "html": "
Stored charge retention
Stored charge retentionStorage time (months) versus Fraction of initial charge (%). Charge retained. Interpretation follows the graphs.0025350675910012Storage time (months)Fraction of initialcharge (%)
Charge retained
" } } ] }