List your loads
Fridge, lights, fan, blanket, laptop, camera batteries, air pump, Starlink, radios, and anything else that drinks power.
Overlanding • Truck Camping • Off-Grid Power
Power your rig past the end of the pavement.
Overland Watts helps you size batteries, solar, inverters, wiring, and camp loads before the trail exposes the weak link in your setup.
Start here
Build the electrical backbone before buying shiny gear.
Most trail power problems start with random parts and wishful math. Start with the loads, then size the battery, charging, inverter, fuses, and wiring around the real mission.
Estimate daily watt-hours
Watts multiplied by hours per day gives the energy your rig needs to store, replace, or survive without.
Choose charging sources
Solar holds the line at camp, DC-DC charging wins while driving, and shore power resets the system between runs.
Protect the system
Use proper fuses, wire size, battery monitoring, ventilation, strain relief, and hard-mounted components.
Free tools
Overland power calculators
Fast planning math for the garage, the driveway, or the night before a trip. Compare setups quickly, then confirm the final build with your real gear specs.
Solar Recharge Calculator
Estimate daily solar harvest after real-world losses from heat, clouds, angle, dust, and charge controller efficiency.
Estimated Daily Harvest
675 Wh/day
Battery Size Calculator
Work backwards from your daily energy use and trip length to estimate the battery capacity you need.
Recommended Minimum
130 Ah
Alternator / DC-DC Charge Calculator
Estimate how much energy your truck can put back into the house battery while you drive.
Energy Recovered
750 Wh from 2 hours driving
Inverter Load Calculator
Estimate DC battery draw from an AC appliance. Useful for laptops, camera chargers, induction cooktops, and small tools.
Battery Draw
27.8A while running • 333Wh used
Wire Voltage Drop Estimator
Estimate voltage drop for 12V and 24V accessory circuits. Always confirm final wiring with a trusted chart or electrician.
Estimated Drop
0.38V drop • 3.2%
Build guides
Field-tested setup blueprints
Use these as starting rigs, then tune the numbers with the calculators above.
Weekend scout
Lean fridge + lights system
- 100Ah LiFePO4 battery
- 100W to 200W portable solar
- 12V fuse block and battery monitor
- Skip the inverter unless AC power is mission-critical
Trail basecamp
The all-around overland rig
- 200Ah LiFePO4 battery bank
- 200W to 400W solar
- 20A to 40A DC-DC charger
- 700W to 1,000W inverter for light AC loads
Deep backcountry
Extended-range power system
- 300Ah+ LiFePO4 battery bank
- 400W+ solar plus alternator charging
- High-output DC-DC charger
- Detailed fuse, bus bar, and monitoring plan
Build lab
The whole system, broken into trail-ready tabs.
This is the part most power sites scatter across twenty articles. Overland Watts puts the whole electrical build path in one place: loads, battery, charging, protection, wiring, and monitoring.
House battery
LiFePO4 is the default for modern rigs because it is lighter, deeper-cycling, and more stable under load than lead-acid.
Charge sources
Use solar for parked days, DC-DC alternator charging for travel days, and shore charging at home or campgrounds.
Distribution
Run battery positive to a main fuse, then to a positive bus bar or fuse block. Run negative through a shunt, then to a negative bus bar.
Loads
Fridge, lights, USB, fan, water pump, Starlink, inverter, and heated gear each need a correctly fused circuit.
DC-DC from the alternator
A DC-DC charger protects the starting battery and gives LiFePO4 batteries the correct charging profile while you drive.
Solar controller
MPPT controllers are the usual pick for serious builds because they harvest better in mixed conditions than simpler PWM controllers.
Shore charger
A plug-in charger keeps the battery topped off at home, in a garage, or at a powered campsite between trail runs.
Charging priority
For truck camping, alternator charging is often the most reliable daily refill. Solar is excellent, but shade and weather always get a vote.
Main fuse
Every positive cable leaving the battery should be fused as close to the battery as practical. The fuse protects the wire, not the gadget.
Bus bars
Bus bars create clean positive and negative distribution points so every accessory is not stacked on the battery terminals.
Fuse block
Use a fused 12V distribution block for small loads like lights, fans, USB outlets, water pumps, radios, and fridge sockets.
Disconnect switch
A master disconnect lets you shut the system down for service, storage, troubleshooting, or emergency isolation.
Size for current and distance
Wire gauge depends on amps and round-trip cable length. Long runs to fridges, inverters, and chargers need heavier wire.
Use real copper
Fine-strand copper or marine-grade tinned copper is worth it in vehicles because vibration and corrosion are part of the job.
Crimp like it matters
Use proper lugs, adhesive heat shrink, a real crimper, grommets through metal, and strain relief where cables move.
Keep inverter runs short
Inverters pull big DC current. Mount them close to the battery, fuse them correctly, and use the cable size the inverter manual requires.
Battery monitor
A shunt-based monitor is the fuel gauge for your electrical system. Voltage alone is a weak state-of-charge indicator for LiFePO4.
Bluetooth tools
Smart chargers, shunts, and solar controllers make troubleshooting much easier when you can see amps, volts, and history from your phone.
Label everything
Label circuits, fuse sizes, wire gauges, and disconnects. Future-you will appreciate it when something quits working in the dark.
Test before trail
Load-test the fridge, inverter, solar, and DC-DC charger at home before you trust the system in the backcountry.
DIY battery box
Build your own removable power box at home.
A battery box is perfect for truck beds, bed campers, RTT setups, trailers, and rigs where you want power without permanently rebuilding the vehicle. Use this guide to plan the layout, parts, protection, and testing sequence before final installation.
Core parts list
- 100Ah to 200Ah LiFePO4 battery with built-in BMS
- Heavy-duty plastic or aluminum enclosure with ventilation and tie-down points
- Main battery fuse: MRBF, MEGA, or Class-T depending on system size
- Positive and negative bus bars rated above expected current
- Shunt-based battery monitor
- 12V fuse block for fridge, lights, USB, fan, pump, and accessories
- Anderson-style quick connector for vehicle charging or external loads
- DC-DC charger if charging from the alternator
- MPPT solar controller if adding portable or roof solar
- Master disconnect switch, lugs, heat shrink, grommets, and cable glands
Simple wiring order
- Mount the battery low and secure inside the box.
- Install the main fuse close to the battery positive terminal.
- Run fused positive to the master disconnect, then the positive bus bar.
- Run battery negative through the shunt, then to the negative bus bar.
- Feed the 12V fuse block from the bus bars with the correct wire and fuse.
- Add ports: fridge socket, USB-C, Anderson connector, solar input, and charger input.
- Label every circuit and record fuse size, wire size, and load name.
- Test each circuit one at a time before installing the box in the vehicle.
Battery box flow
LiFePO4 Battery
Main Fuse
Disconnect
Bus Bars
Fuse Block
Fridge / Lights / USB / Fan
Charging inputs land through the right charger first: alternator into a DC-DC charger, solar into an MPPT controller, and shore power into an AC battery charger. Do not wire raw alternator or solar panel output straight into a LiFePO4 battery.
Gear locker
Component categories worth building around.
These are recommendation lanes, not paid placements. Pick parts by rating, support, warranty, fit, and documentation. Focus on components with clear specifications, strong support, and proven use in mobile power systems.
LiFePO4 house batteries
Premium: Battle Born, Epoch, Victron. Value: LiTime, Renogy, Power Queen. Look for low-temp cutoff, Bluetooth, quality BMS, and real support.
DC-DC chargers
Victron Orion XS, REDARC BCDC, Renogy DC-DC, and Sterling are common paths. Size the charger to the alternator and battery bank.
Panels + MPPT controllers
Rigid roof panels are always there; portable panels can chase sun. MPPT controllers from Victron, Renogy, REDARC, and EcoFlow are common picks.
Fuses, blocks, and bus bars
Blue Sea Systems, Victron Lynx, and quality marine-grade fuse blocks are the clean way to distribute power and protect circuits.
Cable, lugs, and connectors
Use pure copper cable, preferably tinned for exposed vehicle environments. Pair it with proper lugs, adhesive heat shrink, and Anderson-style quick connectors.
Shunts and displays
Victron SmartShunt is a strong premium option. Simpler battery monitors can work, but shunt-based measurement beats guessing from voltage.
AC power only where needed
Victron, Renogy, Samlex, and Xantrex all show up in mobile power builds. Pure sine wave is the move for sensitive electronics.
Enclosures and mounting
Use a tough enclosure, rubber feet, tie-down anchors, cable glands, ventilation where appropriate, and enough service room to inspect every connection.
What to power first
Prioritize the fridge, lights, USB-C charging, fan, water pump, radio, and Starlink Mini before luxury AC loads.
Field notes
Guides worth reading before the trail teaches you the hard way
Practical field notes for sizing, building, troubleshooting, and upgrading mobile power systems.
100Ah vs 200Ah for the real world
Choose capacity based on fridge size, heat, cold nights, solar, and how long your rig sits still.
Read battery sizing guideHow much solar do you need?
Why a 200W panel rarely makes 200W all day, and how shade, dust, and bad angles eat your margin.
Read solar guideFuses, wire size, and not melting your rig
A plain-English overview of why every positive wire leaving the battery needs protection.
Read wiring safety guideDo you actually need an inverter?
When 12V native gear is tougher, when AC power earns its place, and what inverter size changes.
Read inverter guideCold nights and heated blankets
Understand blanket wattage, duty cycles, battery drain, and why insulation matters as much as capacity.
Read winter power guidePortable power station vs DIY battery
A practical comparison for cost, simplicity, charging speed, repairability, and future expansion.
Compare power optionsMore core guides
Build your foundation before buying parts
Overland electrical system guide
The foundation: watts, watt-hours, batteries, solar, inverters, fuses, wire size, and alternator charging.
Start hereWhat is a DC-DC charger?
Understand why lithium systems and modern alternators usually need regulated alternator charging.
Read DC-DC guideDual battery systems explained
Learn starter batteries, house batteries, isolators, DC-DC chargers, grounding, fuses, and system flow.
Read dual battery guideLiFePO4 vs AGM
Compare cost, usable capacity, weight, lifespan, charging speed, and cold-weather considerations.
Compare battery typesPre-run checklist
Before you leave the driveway, camp, or pavement
Use this quick scan before every trip, especially when changing gear or adding a new load.
FAQ
Common overland power questions
Why does the fridge use fewer hours than 24 per day?
Most compressor fridges cycle on and off. A fridge might be powered all day but only actively drawing full wattage part of the time.
Should I size my system from watts or amps?
Use watt-hours for planning because it works across 12V, 24V, USB, and AC devices. Amps still matter for wire size and fuses.
Is LiFePO4 worth it?
For most overland builds, yes. It is lighter, offers more usable capacity, lasts longer, and holds voltage better than lead-acid batteries.
Can I build this system myself?
Many owners build their own 12V systems, but final fuse sizing, wire gauge, crimping, and mounting should be checked carefully before trail use.
Shop the build
Turn research into real build kits.
Start with complete kit paths for weekend rigs, basecamp systems, removable battery boxes, and alternator charging upgrades.