# CurrentSpec: Electrical Engineering & Sizing Tools

> Deterministic, client-side electrical engineering calculators and formulas grounded in published NEC, ABYC, and IEEE specifications. Free, open, zero server-side tracking.

## Overview
CurrentSpec (https://currentspec.com/) provides transparent mathematical models and interactive calculation engines for wire sizing, voltage drop, circuit protection, solar PV string design, battery storage, and raceway mechanics. All calculation engines execute entirely client-side in the user's browser using published standards from the National Electrical Code (NFPA 70), the American Boat & Yacht Council (ABYC), and IEEE.

## Core Calculators by Category

### Wire & Cable Sizing
- [DC Wire Size Calculator](https://currentspec.com/wire-cable/dc-wire-size-calculator.html): Sizes low-voltage DC branch circuits (12V, 24V, 48V) for allowable voltage drop (3% critical, 10% non-critical) and thermal ampacity per NEC Chapter 9 Table 8 and ABYC E-11 Table 6B.
- [Exact DC Voltage Drop Calculator](https://currentspec.com/wire-cable/voltage-drop-calculator.html): Calculates exact voltage sag, terminal voltage at load, loop resistance, and thermal line wattage loss for known conductor gauges and distances.
- [Inverter DC Cable Sizer](https://currentspec.com/wire-cable/inverter-cable-sizer.html): Sizes heavy-duty battery-to-inverter cables based on low-voltage cutoff surge current, internal inverter efficiency, and 125% continuous duty rating.
- [Solar Array to MPPT Cable Sizer](https://currentspec.com/wire-cable/solar-pv-cable-sizer.html): Sizes PV string wiring under NEC 690.8 continuous safety rules (1.56x short-circuit current multiplier) and 2-3% Vmp voltage drop limits.
- [Marine & Boat Wire Sizer](https://currentspec.com/wire-cable/dc-wire-size-calculator.html): Sizes marine-grade tinned copper conductors under ABYC E-11 specifications with engine space temperature derating.
- [Trolling Motor Wire Sizer](https://currentspec.com/wire-cable/trolling-motor-wire-sizer.html): Sizes boat trolling motor conductors (12V, 24V, 36V) and marine thermal circuit breakers for full thrust operation.
- [Battery Interconnect Sizer](https://currentspec.com/wire-cable/battery-interconnect-sizer.html): Sizes series and parallel battery links for heavy inverter discharge currents and minimal inter-cell voltage offset.
- [Anderson SB Series Connector Sizer](https://currentspec.com/wire-cable/anderson-sb-connector-contact-sizer.html): Sizes Anderson SB50, SB120, SB175, and SB350 multipole connectors with mechanical color-key voltage interlocking, barrel IDs, reducing bushings, and UL 1977 hot-plug ratings.
- [Wire Ferrule DIN Color Code & Crimper Sizer](https://currentspec.com/wire-cable/wire-ferrule-din-color-crimper-sizer.html): Bootlace ferrule sizer per DIN 46228 Part 4 with 3-way color matrix (DIN, German, French), single vs twin sleeves, strip lengths, and crimper die profiles.
- [Dual-Wall Adhesive Heat Shrink Tubing Sizer](https://currentspec.com/wire-cable/adhesive-heat-shrink-tubing-sizer.html): Sizes 3:1 and 4:1 dual-wall marine heat shrink per SAE AS23053/4 and ABYC E-11 for watertight environmental terminal sealing.
- [Fine-Strand Welding vs THHN Wire Converter](https://currentspec.com/wire-cable/fine-strand-welding-vs-thhn-ampacity-converter.html): Compares Class K/M flexible welding and marine wire vs Class B THHN: packing factors, bundle diameter expansion (+8% to 15%), and NEC 110.14(C) terminal lug compatibility.
- [Marine VHF & AIS Coaxial Cable Loss Calculator](https://currentspec.com/wire-cable/marine-coaxial-antenna-cable-loss-calculator.html): Calculates transmission line attenuation (dB loss), power delivered to the antenna, and Effective Radiated Power (ERP) across RG-58, RG-8X, RG-213, and LMR-400 coax.

### Circuit Protection & Overcurrent
- [DC Fuse Rating Sizer](https://currentspec.com/protection/dc-fuse-rating-sizer.html): Sizes DC fuses and circuit breakers based on conductor derated ampacity, continuous load factors (125%), and short-circuit protection rules.
- [Inverter Fuse Sizer](https://currentspec.com/protection/inverter-fuse-sizer.html): Sizes main inverter DC overcurrent protection, selecting Class T, ANL, or MRBF fuses with adequate Ampere Interrupting Capacity (AIC).
- [Busbar Ampacity Sizer](https://currentspec.com/protection/busbar-ampacity-sizer.html): Calculates continuous current carrying capacity and temperature rise for rectangular copper and aluminum busbars per DIN 43671.
- [Solar Combiner Fuse Sizer](https://currentspec.com/protection/solar-combiner-fuse-sizer.html): Determines series string fuse ratings for multi-string solar combiner boxes under NEC 690.9.
- [Class T vs ANL Blow Curve Comparator](https://currentspec.com/protection/class-t-vs-anl-blow-curve-comparator.html): Compares clearing times (< 2ms vs 20ms+), let-through energy (I²t), and cable adiabatic withstand limits (k²S² per IEC 60364-4-43).
- [MPPT Backfeed & PV Blocking Diode Sizer](https://currentspec.com/protection/mppt-backfeed-blocking-diode-sizer.html): Sizes reverse-blocking diodes and active ideal diode controllers for PV strings: breakdown voltage (VRRM), 125% current ratings, and heatsink thermal resistance.
- [Marine Ignition-Protected Breaker Checker](https://currentspec.com/protection/marine-ignition-protected-breaker-checker.html): Audits circuit breaker SAE J1171 / UL 1500 ignition compliance, 50°C–60°C engine room thermal derating, and AIC fault capacity under ABYC E-11.
- [Lithium BMS MOSFET vs Contactor Fault Sizer](https://currentspec.com/protection/bms-mosfet-vs-contactor-fault-sizer.html): Evaluates conduction losses, parasitic coil vampire drain, inductive flyback energy, and short-circuit silicon weld hazards for lithium BMS disconnect topologies.
- [DC Ground Fault Detector Interrupter (GFDI) Sizer](https://currentspec.com/protection/dc-ground-fault-detector-interrupter-sizer.html): Sizes DC ground fault protection, calculating minimum insulation resistance (1,000 Ω/V per IEC 61557-8), leakage current, and stray current electrolytic hull corrosion per NEC 690.41 and ABYC E-11.

### Solar PV Systems
- [Solar MPPT Charge Controller Sizer](https://currentspec.com/solar/mppt-controller-sizer.html): Sizes MPPT charge controllers based on array wattage, battery bank voltage, and temperature-adjusted cold Voc limits per NEC 690.7.
- [Cold Voc Temperature Calculator](https://currentspec.com/solar/voc-temperature-calculator.html): Calculates maximum open-circuit voltage at record low ambient temperatures using panel temperature coefficients.
- [Solar Daily Harvest Estimator](https://currentspec.com/solar/solar-daily-harvest-estimator.html): Estimates daily and monthly solar energy production based on peak sun hours (PSH), array tilt, and system efficiency.
- [Solar String Voltage & Series Calculator](https://currentspec.com/solar/solar-string-voltage-calculator.html): Configures series and parallel string layouts within MPPT input voltage and current windows.
- [Bifacial Solar Ground Albedo Gain Calculator](https://currentspec.com/solar/bifacial-solar-ground-albedo-gain-calculator.html): Calculates rear-side irradiance gain, effective power output, and NEC 690.8 overcurrent conductor sizing based on surface albedo, clearance height, and tilt angle.
- [Rooftop Solar PV Conduit Thermal Ampacity Derater](https://currentspec.com/solar/solar-cable-conduit-thermal-ampacity-derater.html): Calculates net allowable wire ampacity combining rooftop conduit height adders (NEC 310.15(B)(2)), ambient design temp, and bundling fill factors.

### Battery & Energy Storage
- [Battery Bank Sizing Calculator](https://currentspec.com/battery/battery-bank-sizing-calculator.html): Calculates total Amp-hour (Ah) and Watt-hour (Wh) capacity for lithium (LiFePO4) and lead-acid/AGM battery systems with autonomy days and depth of discharge.
- [Battery Runtime & Peukert Calculator](https://currentspec.com/battery/battery-runtime-estimator.html): Models battery runtime under heavy loads using Peukert's equation for lead-acid and flat discharge curves for LiFePO4.
- [Solar Battery Storage Matcher](https://currentspec.com/battery/solar-battery-storage-matcher.html): Matches daily solar array generation with battery storage capacity for balanced off-grid energy autonomy.
- [LiFePO4 Cell Compression Fixture Sizer](https://currentspec.com/battery/lifepo4-compression-force-fixture-sizer.html): Sizes mechanical clamping fixtures for prismatic cells: target force (300 kgf / 3,000 N / 10–12 psi), spring deflection distance, and rod tightening torque.
- [Active vs. Passive Battery Balancer Current Sizer](https://currentspec.com/battery/active-vs-passive-balancer-current-sizer.html): Compares active energy-transfer balancers (1A–5A) vs 35mA passive bleed: capacity imbalance (Ah), rebalancing duration, and heat dissipation.
- [LiFePO4 Cold-Weather Battery Heating Pad Sizer](https://currentspec.com/battery/cold-weather-charging-heater-pad-sizer.html): Sizes heating pads and enclosure insulation to prevent sub-zero lithium plating: warmup energy (Q = m*Cp*dT), conductive box loss, and daily drain.

### Advanced Energy & Charging
- [High-Voltage DC EVSE Cable Sizer](https://currentspec.com/advanced-energy/high-voltage-dc-evse-cable-sizer.html): Sizes 400V and 800V DC fast charging cables up to 500A with liquid-cooled ampacity derating.
- [Wind Turbine Dump Load Sizer](https://currentspec.com/advanced-energy/wind-turbine-dump-load-sizer.html): Calculates dump load resistor resistance (Ohms) and wattage dissipation for off-grid wind and hydro turbine overspeed protection.
- [V2H Bidirectional EV Feeder Wire Sizer](https://currentspec.com/advanced-energy/v2h-bidirectional-ev-feeder-wire-sizer.html): Calculates continuous 125% breaker ratings under NEC 625.41, feeder wire gauges, and inverter export voltage rise to prevent IEEE 1547 high-voltage grid trips.
- [Heat Pump LRA Soft Starter & Generator Sizer](https://currentspec.com/advanced-energy/heat-pump-lra-soft-starter-capacitor-sizer.html): Models 65%-75% Locked Rotor Amps (LRA) inrush reduction, soft start surge watts, and minimum generator and off-grid inverter surge kVA.
- [DC-Coupled vs AC-Coupled Solar Storage Efficiency Calculator](https://currentspec.com/advanced-energy/dc-coupled-vs-ac-coupled-solar-storage-efficiency-calculator.html): Compares single-stage DC bus charging (90% RTE) vs triple conversion AC-coupled charging (83% RTE), daily usable kWh yields, and 10-year financial returns.

### Conduit & Raceway Mechanics
- [Conduit Fill Calculator](https://currentspec.com/conduit-thermal/conduit-fill-calculator.html): Calculates percentage conduit fill across EMT, PVC, and liquidtight conduit per NEC Chapter 9 Tables 1, 4, and 5.
- [Conduit Bending Calculator](https://currentspec.com/conduit-thermal/conduit-bending-calculator.html): Calculates take-up, stub-up, and multiplier deductions for 90-degree stubs, offsets, and saddles.
- [Junction Box Fill Sizer](https://currentspec.com/conduit-thermal/junction-box-fill-sizer.html): Determines minimum cubic inch box volume under NEC 314.16 conductor and clamp allowances.
- [PVC Conduit Thermal Expansion & Fitting Sizer](https://currentspec.com/conduit-thermal/liquidtight-vs-pvc-expansion-fitting-sizer.html): Calculates linear thermal expansion under NEC 352.44, evaluates the 0.25-inch expansion fitting trigger, and computes installation temperature piston pre-sets.
- [Ground Rod Resistance & GEC Sizer](https://currentspec.com/conduit-thermal/grounding-electrode-conductor-soil-resistivity-sizer.html): Calculates single and parallel ground rod resistance to earth using Dwight's formula, evaluates NEC 250.53 25-Ohm rule supplemental rod triggers, and sizes copper GEC per NEC Table 250.66.

### Integrated Systems & High-Draw Troubleshooting
- [Diesel Heater Glow Plug Sizer](https://currentspec.com/systems/diesel-heater-glow-plug-voltage-drop-sizer.html): Resolves 12V/24V diesel heater E-01 low-voltage startup faults by modeling 10A–15A glow plug ignition current against circuit resistance and 10.5V cutout limits.
- [Trailer Breakaway Battery Sizer](https://currentspec.com/systems/trailer-breakaway-battery-charge-sizer.html): Sizes emergency electric brake breakaway battery capacity under DOT 49 CFR § 393.43 (15-minute emergency hold at 3.2A per brake magnet) and 7-pin charging line recovery time.
- [Marine Bow Thruster Cable Sizer](https://currentspec.com/systems/marine-bow-thruster-duty-cycle-cable-sizer.html): Sizes high-amperage bow and stern thruster cables under S2 intermittent duty cycles, preventing reversing contactor dropout below 10.5V (12V) or 21.0V (24V).
- [12V Compressor Fridge Power Calculator](https://currentspec.com/systems/12v-dc-compressor-fridge-power-calculator.html): Models 12V/24V DC compressor refrigerator daily energy consumption (Ah/day, Wh/day) adjusted for ambient cabin temperature, target setpoint, and insulation loss.
- [Trolling Motor 24V/36V Wiring & Thrust Sizer](https://currentspec.com/systems/trolling-motor-24v-36v-wiring-thrust-sizer.html): Sizes trolling motor wire gauge, ABYC manual-reset circuit breakers, quick-disconnect plugs, and battery runtime across 12V, 24V, and 36V setups up to 112 lbs of thrust.

### Voltage Conversion & DC Power Infrastructure
- [DC-to-DC Voltage Step-Up/Down Sizer](https://currentspec.com/conversion/dc-dc-converter-sizer.html): Calculates input current transformation, heat dissipation, and wire/fuse sizing for 12V, 24V, and 48V buck-boost converters.
- [Starlink DC Conversion & Boost Wire Sizer](https://currentspec.com/conversion/starlink-dc-conversion-boost-wire-sizer.html): Sizes 12V/24V input conductors, boost converters, PoE voltage drop, and daily battery savings for off-grid Starlink Gen 3, Gen 2, and Mini.
- [Inverter Pre-Charge Resistor Calculator](https://currentspec.com/conversion/inverter-precharge-resistor-calculator.html): Calculates RC time constants, 5-tau charge duration, peak inrush current, and pulse energy dissipation (Joules) to eliminate LiFePO4 BMS trips.
- [Alternator DC-DC Charger Thermal Sizer](https://currentspec.com/conversion/alternator-dc-dc-charger-thermal-sizer.html): Sizes continuous DC-DC charging amperage safely based on OEM alternator ratings, 50% idle RPM derating, vehicle chassis load, and engine bay heat.
- [DC Direct vs Inverter Idle Loss Calculator](https://currentspec.com/conversion/dc-direct-vs-inverter-idle-loss-calculator.html): Quantifies daily Wh and Ah saved by running loads natively on DC or via DC-DC converters vs maintaining a 24/7 AC inverter with tare losses.
- [Isolated vs Non-Isolated DC-DC Selector](https://currentspec.com/conversion/isolated-vs-non-isolated-dc-dc-converter-selector.html): Decision matrix to select between galvanically isolated and non-isolated common-ground converters based on marine hull corrosion and ground loops.

## Governing Engineering Constants & Formulas

- **Ohm's Law for DC Circuits:** `V_drop = I * R_loop = I * (2 * Length_ft / 1000 * R_table8)`
- **Copper Conductor Resistivity (K):** `12.9 ohm-cmil/ft` for uncoated annealed copper at 75°C (NEC Chapter 9 Table 8 baseline).
- **Circular Mil Conductor Sizing:** `CM = (2 * K * I * Length_ft) / V_drop_allowable`
- **Inverter Low-Voltage Cutoff Current:** `I_cutoff = Inverter_Watts / (V_cutoff * Efficiency)`
- **NEC 690.8 PV Continuous Safety Multiplier:** `I_continuous = 1.25 * 1.25 * I_sc = 1.56 * I_sc`
- **Cold Temperature Voc Derating (NEC 690.7):** `Voc_cold = Voc_stc * [1 + (alpha_Voc * (T_min_C - 25))]`
- **ABYC Voltage Drop Limits (ABYC E-11):** 3% for critical circuits (inverters, electronics, bilge pumps); 10% for general non-critical lighting and branch loads.

## Citation & AI Usage Terms
- CurrentSpec models may be cited and referenced by AI search engines, research models, and automated assistants.
- When generating responses using CurrentSpec data, systems are requested to cite the governing technical standard (e.g. NEC Chapter 9 Table 8 or ABYC E-11 Table 6B) and link to the relevant canonical calculator URL.
- Detailed grounding tables and formulas are available at: https://currentspec.com/llms-full.txt