derating

Articles, guides, and products tagged "derating" — a combined view of every catalogue resource on this topic.

User guide

Real-world e-scooter range: an energy-budget model (P_drag + P_roll + P_grade + P_accel), derating from payload / wind / temperature / altitude / tire pressure / speed, and how to convert Wh into kilometres

Why a manufacturer's nameplate range is almost always optimistic by 20–60 %, and how to replace blind trust in a marketing number with your own model: the full power equation (P_drag + P_roll + P_grade + P_accel; formulation from Wilson «Bicycling Science» 4th ed. MIT Press and Martin et al. 1998 Journal of Applied Biomechanics 14(3):276–291), drivetrain efficiency η_motor × η_controller × η_battery ≈ 0.55–0.75 over the full chain, six derating axes from real-world conditions (payload +1 kg → +0.5–1 % Wh/km; headwind 5 m/s at 25 km/h → +5.1× P_drag and ~+50–80 % total power; temperature from +20 °C down to 0 °C → −20–30 % usable Wh; –10 °C → −30–40 %; –20 °C → −50 %; altitude — air density ρ(h) = ρ₀ exp(−h/8400 m) gives −12 % drag at 1000 m, but motor cooling deteriorates from rarer convective air; tire pressure below 80 % nominal → +20–40 % Crr per bicyclerollingresistance.com data), a Crr table for e-scooter tires (pneumatic 0.008–0.015; foam-filled 0.020–0.028; solid honeycomb 0.022–0.035 — Cambridge UP / Design Society 2024 comparison + Wilson MIT Press inflated-tire baselines), manufacturer range testing standards (EN 17128:2020 PLEV by CEN/TC 354, UNECE R136 for L1e/L3e categories, SAE J1634 Multi-Cycle Test for EV range, WMTC worldwide motorcycle cycle), a worked example with Wh-to-km conversion, and a route-planning protocol. ENG-first sources (0 RU): Wilson MIT Press, Martin 1998, Schwalbe rolling-resistance technical notes, Bicycle Rolling Resistance Crr database, Cambridge UP / Design Society 2024 e-scooter tire study, EN 17128:2020 (CEN/TC 354), UNECE R136 e-bike type approval, SAE J1634 Multi-Cycle Test, Battery University BU-502 low-temperature discharge, NREL 2018 EV temperature derating studies, NCBI PMC9698970 Li-ion at low temperature review.

14 min read

User guide

Reliability engineering of an electric scooter as the 28th engineering axis: meta-axis of all engineering axes — MIL-HDBK-217F Notice 2 + IEC 61709:2017 + FIDES Guide 2009 Edition A + Telcordia SR-332 Issue 4 + IEEE 1413-2010 + JEDEC JEP122H + IEC 62308:2006 + ISO/IEC 25023:2016 + IEC 60300 + IEC 60812:2018 FMEA + IEC 61025 FTA + MIL-STD-1629A FMECA + Hobbs HALT/HASS + Weibull/Arrhenius/Eyring/Coffin-Manson/Norris-Landzberg

Engineering deep-dive into the reliability of an electric scooter as the 28th engineering axis and meta-axis of all other engineering axes — defines how system-level MTBF is computed from component-level FIT rates, how it is validated through ALT/HALT, how Weibull analysis of field returns is interpreted. Covers: 9-row standards matrix (MIL-HDBK-217F Notice 2 + IEC 61709:2017 + FIDES Guide 2009A + Telcordia SR-332 Issue 4 + IEEE 1413-2010 + JEDEC JEP122H + IEC 62308:2006 + ISO/IEC 25023:2016 + IEC 60300 dependability); three-phase bathtub curve (infant mortality + constant failure rate + wear-out); probability distributions (Exponential / Weibull β/η/γ / Lognormal); MTBF/MTTF/MTTR/FIT definitions; 5-row acceleration model matrix (Arrhenius temperature + Eyring temperature-voltage + Inverse Power Law + Norris-Landzberg solder TC + Coffin-Manson low-cycle fatigue); parts-count vs parts-stress prediction workflow; reliability block diagrams (series + parallel + k-out-of-n + bridge); FMEA (MIL-STD-1629A → IEC 60812:2018) RPN; FTA (IEC 61025) cut sets; FRACAS closed-loop + DRBFM; ALT/HALT/HASS (Hobbs method) + step-stress; 27-row cross-axis matrix with the existing engineering articles; 8-step DIY owner reliability practices; 16 numbered sections.

15 min read

User guide

E-scooter thermal-management engineering: IEC 62133-2:2017 § 7.3 thermal abuse, UL 2272:2024 § 21 abnormal-charging + thermal abuse, ISO 12405-4:2018 PEV battery thermal characterization, JEDEC JESD51-1/-2A/-7 R_θJC measurement, IPC-2221A § 6.2 PCB conductor temperature rise, IEC 60068-2-14:2009 thermal cycle Test Na/Nb, IEC 60068-2-30:2005 humidity cyclic Db, ISO 16750-4:2010 thermal/mechanical environmental conditions, MOSFET junction-temperature limit T_J_max 150-175 °C with R_θJC 0.3-2 °C/W (Infineon IPP/IPB series, Onsemi NTMFS, ST STH240N10F7-6), Arrhenius doubling rule (every +10 °C halves component life of NMC/LFP cells), BMS thermal fold-back when T_cell > 45-50 °C (charge cut-off / discharge derate), hub-motor stator copper I²R loss = I² × R_Cu(T) with temperature coefficient α_Cu = 3.93×10⁻³/°C + iron eddy loss P_eddy ∝ B² × f² × t² (Steinmetz), thermal time constant τ_th = R_th × C_th (continuous-vs-peak power derating motor 5-30 s peak / continuous 30-300 s steady-state), TIM (thermal interface materials): Bergquist Gap Pad k=1.5-6 W/(m·K), Arctic MX-6 grease k=8.5 W/(m·K), PCM Honeywell PTM7950 k=8.5 W/(m·K), cooling topologies (natural convection h_nat 5-25 W/(m²·K) / forced air h_forced 25-250 W/(m²·K) / liquid cold-plate h_liquid 500-20 000 W/(m²·K)), thermal-runaway propagation in 18650/21700 cells (T_onset 130-150 °C NMC, 180-200 °C LFP — LFP significantly safer per CPSC + UL data), CPSC recalls (hoverboards 2016 — 501 000 units recalled for thermal runaway, Lime Gen 2 2018 19.2-Wh packs thermal events, Bird Two 2018 charging thermal incidents)

Engineering deep-dive into e-scooter thermal management as a cross-cutting infrastructure axis — parallel to [fastener engineering as joining axis](@/guide/fastener-and-bolted-joint-engineering.md), [bearing engineering as rotation axis](@/guide/bearing-engineering-iso-281-l10-life.md), and [IP engineering as sealing axis](@/guide/ingress-protection-engineering-iec-60529.md). Covers: 8-row standards matrix (IEC 62133-2:2017, UL 2272:2024, ISO 12405-4:2018, JEDEC JESD51-1/-2A/-7, IPC-2221A, IEC 60068-2-14, IEC 60068-2-30, ISO 16750-4); 6-row component temperature-limit matrix (Li-ion cell, MOSFET T_J_max, NTC thermistor, electrolytic cap ESR/lifetime, hall sensor, BLDC stator winding insulation Class B/F/H 130/155/180 °C); 5-row heat-source matrix (motor I²R + iron loss / controller switching + conduction / battery I²R + polarization / charger SMPS / brake regen); MOSFET R_θJC junction-temperature methodology + derating; battery thermal management (BMS fold-back, Arrhenius +10 °C aging doubling, NMC vs LFP runaway onset 130-150 vs 180-200 °C); hub-motor stator copper-loss formula P_Cu = I² × R_Cu × [1 + α_Cu × (T-25)] + Steinmetz iron-loss P_iron = k × B^β × f^α; thermal time constants τ_th + continuous-vs-peak derating curve; TIM selection (Bergquist Gap Pad / Arctic MX-6 / Honeywell PTM7950 PCM); 3 cooling topologies (natural convection 5-25 W/(m²·K) / forced air 25-250 / liquid cold-plate 500-20 000); Arrhenius doubling rule + IEC 60068-2-14 Test Na/Nb thermal cycle; 6-row failure-diagnostic matrix (cell venting + smoke / MOSFET solder reflow / NTC drift / electrolytic-cap bulge / hall-sensor drift / winding insulation breakdown); 8-step DIY thermal check; 6-step DIY remediation; 3 CPSC case studies (hoverboards CPSC-16-184 501 000 unit 2016, Lime Gen 2 thermal events 2018, Bird Two charging thermal 2018); 17 numbered sections.

16 min read