Enter your battery voltage, max current and cable length — instantly get correct AWG wire size, fuse rating, fuse type and voltage drop analysis. Free, no signup, works offline.
🔋 12V / 24V / 48V✅ AWG + Fuse📈 Voltage Drop🔒 NEC Standards⚡ LiFePO4 Ready
AWG
Wire Gauge
Fuse
Type + Rating
V Drop
% Analysis
FREE
Always Free
① Enter Your System Details
Volts
Amps
Meters
Amps
② Results
📈 Voltage Drop Analysis
0%Good <3%Warn 5%Bad >10%
🔥 Fuse Type Recommendation
📏 AWG Wire Reference Table
🔒 All Calculations Follow NEC + ABYC Standards
Wire gauge recommendations are based on National Electrical Code (NEC) and American Boat and Yacht Council (ABYC) standards. Fuse sizing follows the 125% continuous load rule. Always verify with a qualified electrician for safety-critical installations.
🔋 Works for All Battery Types
LiFePO4, Li-ion 18650, Lead Acid, AGM, Gel, NiMH — this calculator works for any DC battery system. Enter your pack voltage and maximum discharge current (C-rate × Ah) for accurate results.
When I first started building my own lithium battery packs, I spent hours searching for a reliable tool that could tell me the exact wire gauge and fuse size I needed. Most online calculators were either too basic, showed outdated AWG charts, or did not account for voltage drop properly. That is exactly why I built this comprehensive Battery Pack Wire Gauge and Fuse Size Calculator on ToolsCoops.
Whether you are building a 12V camper van system, a 48V e-bike battery pack, a 24V solar storage system, or an 18650-based DIY power bank, this calculator handles all the math using industry-standard NEC and ABYC formulas.
Why Wire Gauge Matters for Battery Packs
Using the wrong wire gauge in a battery system is one of the most dangerous mistakes a builder can make. Undersized wire creates resistance, generates heat, and in worst cases can melt insulation and cause fires. Each AWG size has a maximum current rating — exceed it and you are creating a potential hazard. This calculator ensures you always use wire that can safely handle your system's maximum current with an appropriate safety margin.
How to Calculate Wire Gauge for Battery Systems
Determine your system voltage (12V, 24V, 48V, etc.)
Calculate maximum continuous current — for lithium packs, this is C-rate × Ah capacity
Measure your total cable run — one-way length from battery to load
Choose your acceptable voltage drop — 3% is standard for most applications
Apply the voltage drop formula: V_drop = (2 × Length × Current × Resistance_per_meter)
Select the next larger AWG size to stay within your voltage drop budget
Fuse Sizing Rules for Battery Packs
Fuses protect the wire, not the device. The golden rule of fuse sizing is to use a fuse rated at 125% to 150% of the maximum continuous current, but never exceeding the wire's current rating. For a 40A continuous circuit, use a 50A fuse on wire rated for at least 50A. Always place fuses as close to the positive battery terminal as possible — within 18 inches for marine and RV applications.
Understanding Fuse Types
Blade fuses (ATO/ATC) — for circuits up to 40A, inexpensive and widely available
MIDI fuses — for 30A to 100A circuits, compact size
ANL fuses — for high current from 80A to 500A, used on main battery cables
MEGA fuses — for 40A to 500A, bolt-down style for reliability
Class T fuses — for critical lithium systems, extremely fast blow time
Voltage Drop — How Much is Too Much?
Voltage drop is the reduction in voltage along a conductor due to its resistance. For 12V systems, a 3% drop equals 0.36V — meaning your devices only receive 11.64V instead of 12V. For sensitive electronics, keep drop below 2%. For general power circuits like lights and fans, 3% to 5% is acceptable. For 48V systems, the same 3% equals 1.44V, which has proportionally less impact on device performance.
❓ Frequently Asked Questions
How do I calculate wire gauge for my battery pack?+
Enter your battery voltage, maximum current and one-way cable length. The calculator uses the voltage drop formula and NEC ampacity tables to recommend the minimum and recommended AWG wire size.
What fuse size do I need for a 100A battery system?+
For a 100A continuous system, you need a 125A fuse (100A × 125%). Use an ANL or MEGA fuse rated 125A to 150A. Place it within 45cm of the positive battery terminal.
What is the difference between AWG and mm² wire sizes?+
AWG (American Wire Gauge) is used in USA and some other countries. Lower AWG number means thicker wire — 4 AWG is thicker than 8 AWG. MM² is the metric equivalent. This calculator shows both AWG and approximate mm² equivalents.
Can I use this for lithium LiFePO4 battery packs?+
Yes! This calculator works perfectly for LiFePO4, Li-ion 18650, lead acid, AGM and any DC battery system. Enter your pack voltage and maximum discharge current (Ah × C-rate) for accurate results.
How close to the battery should the fuse be?+
Place the fuse within 45cm (18 inches) of the positive battery terminal for marine and RV applications. For home battery storage, within 1.5 meters is acceptable. The closer to the battery, the more wire is protected.
Should I use copper or aluminum wire for battery cables?+
Use copper (CU) for battery cables wherever possible. Copper has lower resistance and better conductivity than aluminum. If using aluminum, go 2 AWG sizes larger than the copper recommendation. Aluminum is only used in large fixed installations to save cost and weight.
What wire gauge for a 48V 30A battery system?+
For a 48V 30A system with 2 meter cable run, 10 AWG copper wire is typically sufficient. The 48V voltage means less voltage drop concern for the same power. Enter your exact specs in the calculator for precise results.
What is voltage drop and why does it matter?+
Voltage drop is the reduction in voltage along a cable due to resistance. At 12V with 3% drop, devices only get 11.64V instead of 12V. This causes motors to run slower, inverters to malfunction, and LEDs to dim. Keep drop below 3% for most systems.
Can I use a larger fuse for more protection?+
Never use a fuse larger than the wire's current rating. The fuse protects the wire — an oversized fuse will not blow before the wire overheats. Always size the fuse to match or be slightly below the wire's ampacity rating.
Is this calculator free to use?+
Yes, 100% free forever. No signup, no account, no watermark, no hidden fees. ToolsCoops tools are always free for everyone worldwide.
