{"$schema":"nativecad-dfm-pack/1","id":"battery-systems","title":"Battery systems: cells, joining, modules, packs, HV safety, tests and motorsport ES","sector":"battery-systems","version":"2026-11-04","summary":"How high-performance lithium-ion systems are made and what that demands of the CAD: cell envelopes and swelling, tab and busbar joining, holders and end plates, cold plates, runaway barriers, HV spacing, UN 38.3 and R100 tests, and FIA, Formula E, WEC and Formula Student rules, each with its year.","aliases":["battery","battery pack","battery module","lithium ion","li-ion","cell holder","busbar","bms","thermal runaway","18650","21700","4680","pouch cell","prismatic cell","energy store","ers battery","tab welding","cold plate","accumulator"],"crossSector":false,"size":"core","sources":[{"id":"fia-2026-c21","title":"FIA 2026 F1 Regulations, Section C Technical, Issue 21 (2026-10-19)","accessed":"2026-11-04","url":"https://www.fia.com/system/files/documents/fia_2026_f1_regulations_-_section_c_technical_-_iss_21_-_2026-10-19.pdf","note":"PDF scrambles sub-article numbers; wording read from the text."},{"id":"fs-rules-2026","title":"Formula Student Rules 2026 v1.0 (Formula Student Germany)","accessed":"2026-11-04","url":"https://www.formulastudent.de/fileadmin/user_upload/all/2026/rules/FS-Rules_2026_v1.0.pdf"},{"id":"jsae-ev-2026","title":"JSAE 2026 EV Design Guide v2 (Formula SAE based; renames accumulator container to TBC, segment to module)","accessed":"2026-11-04","url":"https://preopening.jsae.or.jp/files_publish/page/525/2026_EV_DesignGuide_ver2.pdf"},{"id":"un-r100-02","title":"UN Regulation No. 100, 02 series, MLIT copy (annexes 8A to 8I read)","accessed":"2026-11-04","url":"https://www.mlit.go.jp/jidosha/un/UN_R100.pdf","note":"Older series; 05 series entered into force 2025-09-26 and changes propagation requirements."},{"id":"fmvss-305","title":"49 CFR 571.305 FMVSS 305 Electric-powered vehicles","accessed":"2026-11-04","url":"https://www.law.cornell.edu/cfr/text/49/571.305"},{"id":"un383-report","title":"UN 38.3 test report quoting ST/SG/AC.10/11/Rev.7 section 38.3 verbatim (Toyota BTO-074B pack)","accessed":"2026-11-04","url":"https://toyota.jp/pages/contents/cwalks/aircraft/pdf/rep_un_38_3_bto_074b.pdf","note":"UN Manual fetch refused; this report restates it. Check current revision."},{"id":"samsung-50e","title":"Samsung SDI INR21700-50E cell specification V1.0","accessed":"2026-11-04","url":"https://shop.aceongroup.com/cdn/shop/files/RLII-CSI-1618_Samsung_50E_DATASHEET.pdf"},{"id":"molicel-p42a","title":"Molicel INR-21700-P42A product data sheet","accessed":"2026-11-04","url":"https://www.rcscomponents.kiev.ua/datasheets/INR21700P42A-V4-80092.pdf"},{"id":"sony-vtc6","title":"Sony US18650VTC6 technical information rev 0.1 (2015)","accessed":"2026-11-04","url":"https://www.kronium.cz/uploads/SONY_US18650VTC6.pdf"},{"id":"bd-expansion","title":"Battery Design: cell electrode pressure and expansion","accessed":"2026-11-04","url":"https://www.batterydesign.net/battery-cell/cell-electrode-pressure-and-expansion/"},{"id":"bd-module","title":"Battery Design: battery module design","accessed":"2026-11-04","url":"https://www.batterydesign.net/module/"},{"id":"bd-busbars","title":"Battery Design: busbars","accessed":"2026-11-04","url":"https://www.batterydesign.net/electrical/high-voltage-system/busbars/"},{"id":"bd-runaway","title":"Battery Design: thermal runaway","accessed":"2026-11-04","url":"https://www.batterydesign.net/safety/thermal-runaway/"},{"id":"bd-creepage","title":"Battery Design: creepage and clearance","accessed":"2026-11-04","url":"https://www.batterydesign.net/electrical/creepage-and-clearance/"},{"id":"das-2018","title":"Das, Li, Williams, Greenwood: Joining technologies for automotive battery systems manufacturing, World Electric Vehicle J. 9(2), 2018 (CC BY)","accessed":"2026-11-04","url":"https://wrap.warwick.ac.uk/id/eprint/93286/13/WRAP-joining-technologies-automotive-battery-systems-Das-2018.pdf"},{"id":"amada-tab","title":"AMADA WELD TECH: battery welding, using lasers for tab welding (equipment-maker practice note)","accessed":"2026-11-04","url":"https://amadaweldtech.com/blog/battery-welding-using-lasers-for-battery-tab-welding-applications/"},{"id":"ljmu-hilumin","title":"Effect of a ring-shaped laser beam on the weldability of aluminum-to-hilumin for battery tab connectors, J. Laser Appl. 35, 042038 (2023)","accessed":"2026-11-04","url":"https://researchonline.ljmu.ac.uk/id/eprint/21976/1/Effect%20of%20a%20ringshaped%20laser%20beam%20on%20the%20weldability%20of%20aluminum-to-hilumin%20for%20battery%20tab%20connectors.pdf"},{"id":"nasa-darcy-2015","title":"Darcy (NASA JSC): Safe, High Performing Li-ion Battery Designs, summary of 2015 findings, NASA Aerospace Battery Workshop","accessed":"2026-11-04","url":"https://ntrs.nasa.gov/api/citations/20150020936/downloads/20150020936.pdf"},{"id":"sr-2026-window","title":"Alkhatib et al., Scientific Reports, article in press 2026: 2170 cell thermal window","accessed":"2026-11-04","url":"https://www.nature.com/articles/s41598-026-40953-1_reference.pdf"},{"id":"catalog-60664","title":"Equipment catalogue table of creepage distances, stated as taken from IEC 60664-1 with a 1.5 mm floor","accessed":"2026-11-04","url":"https://www.tamhash.co.il/catalog400A/files/assets/basic-html/page-535.html","note":"Secondary reproduction: verify against the paywalled IEC 60664-1 before release."},{"id":"iec-60664-1","title":"IEC 60664-1 Insulation coordination for equipment within low-voltage supply systems (paywalled; scope cited, clauses not read)","accessed":"2026-11-04"}],"entries":[{"id":"cell-18650-envelope","kind":"dimension","tier":1,"title":"18650 cell envelope: datasheet maximum","summary":"Model the 18650 at its datasheet maximum: VTC6 is 18.50 mm max dia x 65.20 mm max long with sleeve, 46.5 g average. Pockets clear the maximum, never the nominal 18.0 x 65.0.","applies":["18650","cell holder"],"basis":"SRC: Sony US18650VTC6 technical information 1.2.2, 1.2.3. Other 18650s differ; read that cell's sheet.","sources":["sony-vtc6"],"tags":["cylindrical"],"value":{"table":[{"cell":"Sony US18650VTC6","dia_max_mm":18.5,"length_max_mm":65.2,"mass_g":46.5}]},"see":["electronics/battery-18650-compartment","desktop-robots/battery-18650-bay"]},{"id":"cell-21700-envelope","kind":"dimension","tier":1,"title":"21700 cell envelope: two datasheets differ by 0.45 mm","summary":"21700 envelope varies by maker: Samsung 50E max dia 21.25 x 70.80 mm, 69.5 g max; Molicel P42A max dia 21.7 x 70.2 mm, 70 g max. Size holder bores for the chosen cell, and treat the name as nominal only.","applies":["21700","cell holder"],"basis":"SRC: Samsung 50E spec V1.0 sec 3 and Fig 1 (with sleeve); Molicel P42A data sheet, physical characteristics.","sources":["samsung-50e","molicel-p42a"],"tags":["cylindrical"],"value":{"table":[{"cell":"Samsung INR21700-50E","dia_max_mm":21.25,"height_max_mm":70.8,"mass_max_g":69.5},{"cell":"Molicel INR-21700-P42A","dia_max_mm":21.7,"height_max_mm":70.2,"mass_max_g":70}]},"see":["automotive/cell-module-sizes-ev"]},{"id":"swell-allowance-life","kind":"rule","tier":1,"title":"Swelling allowance over cell life","summary":"Stack and cell thickness grow 10 to 20% over life in prismatic and pouch cells. Reserve that travel in the stack, with pads or a sprung end plate, rather than building the module to the new-cell stack height.","applies":["prismatic cell","pouch cell","battery module"],"basis":"SRC: Battery Design expansion and module pages state 10-20%. LFP is described as far lower, silicon anodes as higher, no figures given.","sources":["bd-expansion","bd-module"],"tags":["stack"],"value":{"min":10,"max":20,"unit":"%"}},{"id":"pouch-fixing-limits","kind":"rule","tier":1,"title":"Pouch cell fixing: 80% of face, tabs unloaded","summary":"Fix pouch cells by their large faces over at least 80% of each face used; tabs carry no mechanical load and must not press into the pouch. Stress limit at 40/40/20 g: 0.05 MPa shear, 1.0 MPa compression on 80% of the face area.","applies":["pouch cell","cell holder"],"basis":"SRC: FS Rules 2026 EV 5.5 (pouch cell clause; sub-number scrambled in extraction). A competition rule, and a usable conservative sizing case elsewhere.","sources":["fs-rules-2026"],"tags":["mounting"],"value":{"table":[{"limit":"fixed area of face","value":">= 80 %"},{"limit":"shear on cell","value":"<= 0.05 MPa"},{"limit":"compression on cell","value":"<= 1.0 MPa"},{"limit":"cells in series without stress analysis","value":"<= 8"}]}},{"id":"can-polarity-weld","kind":"rule","tier":1,"title":"Cylindrical can is negative and thin: weld, never solder","summary":"On 18650 and 21700 cells the steel can is the negative terminal, typically about 0.3 mm thick in the wall. Weld leads, never solder to the cell (Samsung 2.1.1), and avoid excess force on the negative end. A busbar touching the shoulder shorts to negative.","applies":["18650","21700","busbar"],"basis":"SRC: Samsung 50E spec 5.2.1 and 2.1.1; can thickness from AMADA practice note. LJMU quotes 0.5 mm Hilumin casings, so measure. Shoulder short: EST from can polarity.","sources":["samsung-50e","amada-tab","ljmu-hilumin"],"tags":["polarity"],"value":{"typical":0.3,"unit":"mm"}},{"id":"cell-gap-propagation","kind":"rule","tier":1,"title":"Cell-to-cell gap against propagation: 0.5 mm failed, 3 mm design held","summary":"NASA found about 0.5 mm 18650 spacing too tight; the non-propagating tool battery used 3 mm with G10/FR4 capture plates and 100 um mica sleeves. Proposed LLB fix: 80 cells to 65, up to ~2 mm. Touching cells nearly assure propagation.","applies":["18650","cell holder","thermal runaway"],"basis":"SRC: Darcy, NASA JSC 2015, tests of specific 18650 cells in small batteries. Gap alone is not sufficient, and higher-energy cells rupture more.","sources":["nasa-darcy-2015"],"tags":["spacing"],"value":{"value":3,"unit":"mm","note":"one tested 18650 design, with capture plates and mica; 2 mm proposed, untested"},"see":["automotive/cell-module-sizes-ev"]},{"id":"vent-direction","kind":"rule","tier":1,"title":"Point cell vents down a clear path away from neighbours","summary":"Direct all cell vents one way, into a plenum clear of adjacent cells, with a tortuous path to screened pack ports: NASA ports read 66 to 69 C, even in a redesign that still propagated. Dead-ended ejecta pooled by a wall; in the baseline test one housing base hit 354 C.","applies":["thermal runaway","battery module"],"basis":"SRC: Darcy 2015 design rules and measured temperatures for small 18650 batteries; ejecta is conductive, so insulate the plenum. Not scaled to large packs.","sources":["nasa-darcy-2015"],"tags":["plenum"],"value":{"min":66,"max":69,"unit":"C"}},{"id":"tab-vs-can-thickness","kind":"rule","tier":1,"title":"Tab thickness against can thickness for laser welds","summary":"Keep the tab thinner than the can or terminal it lands on: a practice rule is 50 to 60% of a 0.3 mm can, so about 0.15 to 0.18 mm. The weld must not penetrate the can. Coin thicker tabs down locally at the weld.","applies":["tab welding","busbar"],"basis":"SRC: AMADA practice note for the 50-60% rule and no-penetration; Das 2018 confirms tab thinner than terminal. 0.15-0.18 mm is arithmetic.","sources":["amada-tab","das-2018"],"tags":["laser"],"value":{"min":50,"max":60,"unit":"%"}},{"id":"busbar-current-density","kind":"rule","tier":1,"title":"Busbar section: start at 5 A/mm2 of copper","summary":"Size a copper pack busbar first at 5 A per mm2 continuous, a figure from the 5.9 A/mm2 fit slope of five EV busbars, then run electrothermal analysis. Aluminium needs about 1.6 times the area.","applies":["busbar"],"basis":"SRC: Battery Design busbars page. A starting point for a cooled EV pack, not a limit. Peak current and connector temperature can govern.","sources":["bd-busbars"],"tags":["current-density"],"value":{"value":"5 A/mm2 Cu to start; 5.9 A/mm2 fit to 5 EV busbars","unit":"text"}},{"id":"cell-temp-window","kind":"rule","tier":1,"title":"Cell thermal window and maximum spread","summary":"Design the thermal path to hold cells near 15 to 35 C with under 3 to 5 C spread across the module. Above about 130 C, exothermic reactions begin. FS caps measured cell temperature at 60 C or the datasheet limit, if lower.","applies":["cold plate","battery module"],"basis":"SRC: Alkhatib 2026 for window, stated as usual range, in press; Battery Design for 130 C; FS EV 5.8. Motorsport duty may run hotter: not published.","sources":["sr-2026-window","bd-runaway","fs-rules-2026"],"tags":["temperature"],"value":{"min":15,"max":35,"unit":"C"}},{"id":"creepage-table","kind":"dimension","tier":1,"title":"Creepage by rated insulation voltage Ui, pollution degree, material group","summary":"Creepage mm from IEC 60664-1 as tabulated by a catalogue against rated insulation voltage Ui: 400 V PD2 2.5 (I) to 5 (IIIa), PD3 6.3 to 8; 800 V PD2 5 to 10, PD3 12.5 to 16; 1000 V PD2 6.3 to 12.5, PD3 16 to 20. Treat the pack interior as PD3; double for reinforced insulation.","applies":["busbar","battery pack"],"basis":"SRC: Catalogue column is rated insulation voltage Ui, not working voltage; verify on the IEC text. PD3 default and doubling from Battery Design, a view, not a clause. See automotive for clearance.","sources":["catalog-60664","bd-creepage","iec-60664-1"],"tags":["iec-60664"],"value":{"table":[{"V":400,"pd2_I":2.5,"pd2_II":3.6,"pd2_III":5,"pd3_I":6.3,"pd3_II":7.1,"pd3_IIIa":8},{"V":800,"pd2_I":5,"pd2_II":7.1,"pd2_III":10,"pd3_I":12.5,"pd3_II":14,"pd3_IIIa":16},{"V":1000,"pd2_I":6.3,"pd2_II":9,"pd2_III":12.5,"pd3_I":16,"pd3_II":18,"pd3_IIIa":20}]},"see":["automotive/busbar-clearance-creepage"]},{"id":"isolation-resistance","kind":"rule","tier":1,"title":"HV isolation resistance targets","summary":"Road rules require at least 100 ohm/V on DC buses and 500 ohm/V on AC buses, in R100 and FMVSS 305; FS sets 500 ohm/V against max tractive voltage. After immersion or crush this must hold, so keep the creepage dry with drains and seals.","applies":["battery pack","bms"],"basis":"SRC: UN R100 02 series, 5.1; FMVSS 305 S5.3 (standard ends 2027-09-01 for new builds per its text). F1 uses 100/500 to define a live part. Drain clause is EST.","sources":["un-r100-02","fmvss-305","fs-rules-2026","fia-2026-c21"],"tags":["imd"],"value":{"value":"100 ohm/V DC; 500 ohm/V AC","unit":"text"}},{"id":"test-un38-3","kind":"test","tier":1,"title":"UN 38.3 T1 to T8 transport tests and what they want","summary":"T1 11.6 kPa 6 h; T2 72 C and -40 C, 10 cycles; T3 7 to 200 Hz 3 h per axis, up to 8 gn; T4 150 gn 6 ms (or 50 gn 11 ms); T5 under 0.1 ohm at 57 C; T6 9.1 kg from 61 cm on 15.8 mm bar; T7 twice max charge; T8 forced discharge. Seals and welds must survive.","applies":["battery","battery pack","energy store"],"basis":"SRC: Report quoting UN Manual Rev.7 sec 38.3; current revision unchecked. F1 also requires the certificate.","sources":["un383-report","fia-2026-c21"],"tags":["un38.3"],"see":["battery-systems/test-un38-3-table"]},{"id":"f1-2026-es-limits","kind":"rule","tier":1,"title":"F1 2026 Energy Store headline limits (Issue 21)","summary":"F1 2026 ES: 35.0 kg minimum for the ES Main Enclosure mass group; 4 MJ maximum state-of-charge window on track; 8.5 MJ per lap recharge at CU-K HV bus; maximum working voltage 1000 V; UN 38.3 certificate. Rules change by issue.","applies":["energy store","ers battery"],"basis":"SRC: FIA Section C Issue 21, 2026-10-19, C5.2, C5.17 groups (sub-numbers scrambled in PDF). Mass procedure in FIA-F1-DOC-105, not read.","sources":["fia-2026-c21"],"tags":["f1"],"value":{"min":35,"unit":"kg"}},{"id":"fs-accumulator-limits","kind":"rule","tier":1,"title":"Formula Student accumulator limits 2026","summary":"FS 2026: 600 V max, each segment max 120 V, 6 MJ, 12 kg; 80 kW and 500 A at the container; cells and container mounted for 40 g longitudinal, 40 g lateral, 20 g vertical, inside the primary structure. FSAE 2026 renames parts TBC and modules.","applies":["accumulator","fsae","formula student"],"basis":"SRC: FS Rules 2026 EV 2.2, EV 4.1, EV 5.3, T 3.3; JSAE 2026 guide for the rename. FSAE US text not opened: use the event's own rules.","sources":["fs-rules-2026","jsae-ev-2026"],"tags":["fsae"],"value":{"max":600,"unit":"V"}}]}