{
"node": {
"id": "term:string",
"type": "Term",
"label": "String",
"properties": {
"id": "string",
"name": "String",
"aka": [
"battery string",
"series string"
],
"section": "topic-pack",
"definition": "A chain of cells or modules connected in series to reach the system voltage, the basic electrical unit of a large battery. In stationary storage each rack is usually one string of about 1000–1500 V with its own contactors and BMS, and many strings are paralleled on a common DC bus.",
"related": [
"series-parallel",
"pack-voltage",
"stationary-storage",
"parallel-string-current-sharing",
"bms-architecture",
"contactor"
],
"url": "https://lemonergy.com/learn/glossary/string/",
"mentions": [
"bms"
]
}
},
"edges": [
{
"id": "edge:4940",
"source": "term:string",
"target": "topic:topic-pack",
"type": "belongsTo",
"properties": {
"sourceFile": "terms.json"
}
},
{
"id": "edge:4941",
"source": "term:string",
"target": "term:series-parallel",
"type": "relatedTo",
"properties": {
"sourceFile": "terms.json",
"meaning": "Related context; not a causal claim"
}
},
{
"id": "edge:4942",
"source": "term:string",
"target": "term:pack-voltage",
"type": "relatedTo",
"properties": {
"sourceFile": "terms.json",
"meaning": "Related context; not a causal claim"
}
},
{
"id": "edge:4943",
"source": "term:string",
"target": "term:stationary-storage",
"type": "relatedTo",
"properties": {
"sourceFile": "terms.json",
"meaning": "Related context; not a causal claim"
}
},
{
"id": "edge:4944",
"source": "term:string",
"target": "term:parallel-string-current-sharing",
"type": "relatedTo",
"properties": {
"sourceFile": "terms.json",
"meaning": "Related context; not a causal claim"
}
},
{
"id": "edge:4945",
"source": "term:string",
"target": "term:bms-architecture",
"type": "relatedTo",
"properties": {
"sourceFile": "terms.json",
"meaning": "Related context; not a causal claim"
}
},
{
"id": "edge:4946",
"source": "term:string",
"target": "term:contactor",
"type": "relatedTo",
"properties": {
"sourceFile": "terms.json",
"meaning": "Related context; not a causal claim"
}
},
{
"id": "edge:mentions/string/bms",
"source": "term:string",
"target": "term:bms",
"type": "mentions",
"properties": {
"sourceFile": "terms.json",
"method": "build_glossary.mention_index + mentions",
"field": "definition",
"meaning": "Text mention; not a causal claim"
}
},
{
"id": "edge:4948",
"source": "term:string",
"target": "visual:pack",
"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:series-parallel",
"type": "Term",
"label": "Series and parallel connection",
"properties": {
"id": "series-parallel",
"name": "Series and parallel connection",
"aka": [
"xSyP"
],
"section": "topic-pack",
"definition": "Cells in series add their voltages; cells in parallel add their capacities and share current. A pack is described as, for example, 96s4p: 96 groups in series, each of 4 cells in parallel. Series strings need balancing; parallel groups self-balance through their shared terminals.",
"formula": "V = n_s·V_cell, Q = n_p·Q_cell",
"related": [
"module",
"cell-balancing",
"pack-voltage",
"volt",
"fuse"
],
"lesson": "fundamentals/battery-basics/#cell-module-pack",
"example": {
"title": "Assemble an ideal 4s2p pack",
"text": "Eight identical 3.6 V, 5 Ah cells arranged as four series groups with two cells in parallel give 14.4 V nominal, 10 Ah and 144 Wh. Interconnect losses, cell variation and usable voltage limits are additional constraints."
},
"url": "https://lemonergy.com/learn/glossary/series-parallel/",
"mentions": []
}
},
{
"id": "term:pack-voltage",
"type": "Term",
"label": "Pack voltage",
"properties": {
"id": "pack-voltage",
"name": "Pack voltage",
"aka": [
"400 V system",
"800 V system"
],
"section": "topic-pack",
"definition": "The nominal voltage of the full series string, about 400 V in most electric cars and 800 V in newer ones. Doubling the voltage halves the current for the same power, so cables, connectors and losses shrink and charging can be faster.",
"unit": "V",
"related": [
"series-parallel",
"dc-fast-charging",
"high-voltage-interlock",
"insulation-resistance"
],
"url": "https://lemonergy.com/learn/glossary/pack-voltage/",
"mentions": [
"nominal-voltage",
"string"
]
}
},
{
"id": "term:stationary-storage",
"type": "Term",
"label": "Stationary storage",
"properties": {
"id": "stationary-storage",
"name": "Stationary storage",
"abbr": "BESS",
"aka": [
"battery energy storage system",
"ESS"
],
"section": "topic-applications",
"definition": "Batteries installed in a fixed place — a container at a solar farm, a cabinet in a home — to shift energy in time or support the grid. LFP cells dominate because cost per cycle and safety matter more than mass.",
"related": [
"lfp",
"energy-management-system",
"inverter",
"energy-arbitrage",
"long-duration-storage",
"ul-9540a"
],
"url": "https://lemonergy.com/learn/glossary/stationary-storage/",
"mentions": []
}
},
{
"id": "term:parallel-string-current-sharing",
"type": "Term",
"label": "Current sharing between parallel strings",
"properties": {
"id": "parallel-string-current-sharing",
"name": "Current sharing between parallel strings",
"aka": [
"cross-string current sharing",
"string current imbalance",
"circulating current"
],
"section": "topic-pack",
"definition": "How current divides between strings connected in parallel. A string with lower resistance or a different OCV takes more than its share and ages faster, and connecting strings at different voltages drives a circulating current between them. Systems therefore match voltages before closing a string’s contactors and limit total current to what the weakest string can carry.",
"related": [
"string",
"series-parallel",
"internal-resistance",
"open-circuit-voltage",
"contactor",
"cell-to-cell-variation"
],
"url": "https://lemonergy.com/learn/glossary/parallel-string-current-sharing/",
"mentions": []
}
},
{
"id": "term:bms-architecture",
"type": "Term",
"label": "BMS architecture",
"properties": {
"id": "bms-architecture",
"name": "BMS architecture",
"aka": [
"centralised BMS",
"centralized BMS",
"distributed BMS",
"modular BMS",
"master–slave BMS",
"rack BMS"
],
"section": "topic-pack",
"definition": "How a BMS’s electronics are divided across the pack. A centralised BMS wires every cell to one board, suiting small packs; a modular or master–slave design puts a monitoring board on each module reporting to one controller; a distributed design puts electronics on each cell. Stationary systems add tiers: module, rack and system-level BMS.",
"related": [
"bms",
"cell-supervision-circuit",
"bmu",
"wireless-bms",
"string",
"redundant-bms"
],
"url": "https://lemonergy.com/learn/glossary/bms-architecture/",
"mentions": []
}
},
{
"id": "term:contactor",
"type": "Term",
"label": "Contactor",
"properties": {
"id": "contactor",
"name": "Contactor",
"section": "topic-hvsafety",
"definition": "A heavy-duty electrically operated switch that connects the pack to the vehicle or inverter and opens it on fault or shutdown. Packs use at least two, one per pole, plus a pre-charge path to avoid welding them on the first connection.",
"related": [
"pre-charge",
"battery-disconnect-unit",
"pyrofuse",
"bms"
],
"url": "https://lemonergy.com/learn/glossary/contactor/",
"mentions": [
"inverter"
]
}
},
{
"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": "visual:pack",
"type": "Visual",
"label": "Series voltage and parallel capacity",
"properties": {
"title": "Series voltage and parallel capacity",
"summary": "Count series and parallel connections separately.",
"readout": "4S2P: 8 cells, 14.8 V, 10 Ah, 148 Wh.",
"formula": "V_pack = Ns V_cell; Q_pack = Np Q_cell",
"note": "Identical 3.7 V, 5 Ah cells; ideal equal current sharing and no losses.",
"software": {
"status": "reference",
"label": "Reference concept",
"body": "Ideal pack ratings use V_pack = Ns V_cell and Q_pack = Np Q_cell. The core energy helper can multiply these ratings. Imbalance and current sharing require additional models.",
"href": "../fundamentals/capacity-and-c-rate/"
},
"html": "Voltage along one series string