{ "node": { "id": "term:active-balancing", "type": "Term", "label": "Active balancing", "properties": { "id": "active-balancing", "name": "Active balancing", "aka": [ "capacitive balancing", "inductive balancing", "switched-capacitor balancing", "converter-based balancing", "cell bypass" ], "section": "topic-pack", "definition": "Cell balancing that moves charge from fuller cells to emptier ones instead of burning it in resistors. Switched capacitors shuttle charge between neighbours; inductors or transformers carry it further; isolated converters exchange it between one cell and the whole string; bypass switches take a cell out of the string. Currents reach amperes, at the cost of more parts.", "related": [ "cell-balancing", "buck-boost-converter", "bms", "cell-to-cell-variation", "mosfet" ], "url": "https://lemonergy.com/learn/glossary/active-balancing/", "mentions": [] } }, "edges": [ { "id": "edge:5003", "source": "term:active-balancing", "target": "topic:topic-pack", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:5004", "source": "term:active-balancing", "target": "term:cell-balancing", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5005", "source": "term:active-balancing", "target": "term:buck-boost-converter", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5006", "source": "term:active-balancing", "target": "term:bms", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5007", "source": "term:active-balancing", "target": "term:cell-to-cell-variation", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5008", "source": "term:active-balancing", "target": "term:mosfet", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5009", "source": "term:active-balancing", "target": "visual:balancing", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "neighbors": [ { "id": "topic:topic-pack", "type": "Topic", "label": "Modules, packs and battery management", "properties": { "id": "topic-pack", "name": "Modules, packs and battery management", "lede": "From a single cell to a working battery system, and the electronics that keep it safe.", "context": "Make series/parallel architecture explicit.", "example": "Twelve 3.6 V, 5 Ah cells in 6s2p give 21.6 V, 10 Ah and 216 Wh nominally before other restrictions.", "lesson_url": "https://lemonergy.com/learn/fundamentals/cell-architecture/", "lesson_label": "Open cell architecture" } }, { "id": "term:cell-balancing", "type": "Term", "label": "Cell balancing", "properties": { "id": "cell-balancing", "name": "Cell balancing", "section": "topic-state", "definition": "Equalising the state of charge of cells in series, since the pack is limited by its emptiest cell on discharge and its fullest on charge. Passive balancing bleeds charge from high cells through resistors; active balancing moves it between cells.", "related": [ "bms", "series-parallel", "state-of-charge", "cell-to-cell-variation" ], "example": { "title": "Pack average versus cell limits", "text": "Average pack SOC can look acceptable while one series cell reaches its voltage limit. One aggregate SOC state does not demonstrate cell balancing." }, "url": "https://lemonergy.com/learn/glossary/cell-balancing/", "mentions": [ "active-balancing" ] } }, { "id": "term:buck-boost-converter", "type": "Term", "label": "Buck and boost converters", "properties": { "id": "buck-boost-converter", "name": "Buck and boost converters", "aka": [ "buck converter", "boost converter", "step-down converter", "step-up converter", "bidirectional DC/DC converter" ], "section": "topic-data", "definition": "Switch-mode circuits that step a DC voltage down (buck) or up (boost) using a fast switch, an inductor and a capacitor, often above 95% efficient. With transistors in place of diodes the same circuit runs both ways, charging a battery from a bus or discharging into it, as in stationary storage and on-board boosters that let 800 V cars use 400 V chargers.", "related": [ "dc-dc-converter", "pulse-width-modulation", "mosfet", "active-balancing", "split-pack" ], "url": "https://lemonergy.com/learn/glossary/buck-boost-converter/", "mentions": [ "stationary-storage", "capacitor" ] } }, { "id": "term:bms", "type": "Term", "label": "Battery management system", "properties": { "id": "bms", "name": "Battery management system", "abbr": "BMS", "section": "topic-pack", "definition": "The electronics and software that keep a battery inside its safe window: measuring every cell voltage and many temperatures, estimating SOC and SOH, balancing cells, computing current limits, controlling the contactors and reporting over the vehicle network.", "related": [ "state-of-charge", "cell-balancing", "state-of-power", "cell-supervision-circuit", "contactor", "can-bus" ], "lesson": "fundamentals/battery-basics/#cell-module-pack", "url": "https://lemonergy.com/learn/glossary/bms/", "mentions": [ "state-of-health", "cell-voltage" ] } }, { "id": "term:cell-to-cell-variation", "type": "Term", "label": "Cell-to-cell variation", "properties": { "id": "cell-to-cell-variation", "name": "Cell-to-cell variation", "section": "topic-state", "definition": "The spread in capacity, resistance and self-discharge between nominally identical cells, from manufacturing and from unequal temperatures in service. It is why packs need balancing and why grading matches cells before assembly.", "related": [ "cell-balancing", "grading", "end-of-line-testing", "thermal-management" ], "url": "https://lemonergy.com/learn/glossary/cell-to-cell-variation/", "mentions": [ "self-discharge" ] } }, { "id": "term:mosfet", "type": "Term", "label": "MOSFET", "properties": { "id": "mosfet", "name": "MOSFET", "aka": [ "metal–oxide–semiconductor field-effect transistor", "power MOSFET" ], "section": "topic-data", "definition": "A transistor switched by the voltage on its gate, with an on-resistance of milliohms or less in power parts. Low-voltage packs use back-to-back pairs as charge and discharge switches, since each conducts backwards through its body diode; BMS chips use small ones for balancing, and silicon-carbide MOSFETs switch 800 V inverters.", "related": [ "protection-circuit", "pulse-width-modulation", "cell-balancing", "inverter", "buck-boost-converter" ], "url": "https://lemonergy.com/learn/glossary/mosfet/", "mentions": [ "bms" ] } }, { "id": "visual:balancing", "type": "Visual", "label": "The limiting cell matters", "properties": { "title": "The limiting cell matters", "summary": "A pack average can hide a cell that reaches its voltage limit first.", "readout": "Average: 3.93 V. Highest cell: 4.02 V. The highest cell can reach the charge limit first.", "formula": "V_max = max(V₁, V₂, …); V_average = ΣV_i / N", "note": "The 4.2 V ceiling is an example, not universal. Voltage alone does not uniquely determine SOC.", "software": { "status": "reference", "label": "Reference concept", "body": "Cell supervision uses individual voltages. The native Studio battery is an aggregate model; this chart does not claim it simulates cell balancing.", "href": "https://design.lemonergy.com/cosim.html?example=charging-home" }, "html": "
Four cells before balancing
Four cells before balancingCell number versus Cell voltage (V). Individual voltages; Average; Example ceiling. Interpretation follows the graphs.3.713.851.7542.54.153.254.34Cell numberCell voltage (V)
Individual voltagesAverage (dashed)Example ceiling
" } } ] }