12V systems for vehicles that live off-grid
Size the battery bank before you buy the battery
Free calculators and researched gear guidance for overland, van and truck-camper power builds. Battery banks, solar, alternator charging, wiring and fusing, all worked from the arithmetic rather than from a parts list someone else bought.
- Calculators
- 7
- Power stations
- 36
- Gear guides
- 32
- Reference charts
- 9
Start with the arithmetic
Battery bank and solar sizing are where builds go wrong expensively. A bank sized by guesswork is either a thousand dollars of capacity you never use or a fridge that dies on the third morning, and both mistakes cost more than the tool that would have prevented them.
- Battery bank calculator Turn a device load list into the amp-hours you actually need, with usable capacity by chemistry. Open →
- Solar array calculator Panel watts to daily amp-hours by peak sun hours, with an honest derate factor. Open →
- Power consumption calculator Daily watt-hours and amp-hours from every appliance in the build. Open →
- Wire gauge calculator Ampacity and voltage drop by run length, to ABYC E-11 figures. Open →
- Inverter sizing calculator Surge and continuous watts, and the DC current the battery has to supply. Open →
- Payload calculator GVWR headroom against the sticker on your own door jamb. Open →
- Water capacity calculator Gallons per day per person, and the 8.34 lb per gallon that comes with it. Open →
Three complete builds, priced to the dollar
Not shopping lists. Finished systems, grouped by function, with every component priced and a real running total, from a plug-and-play weekend setup to a full-time off-grid rig.
- Beginner build $1,057 A sealed power station, a folding panel and a fridge. Nothing cut, nothing drilled. See the build →
- Intermediate build $2,786 A wired 100Ah bank, 50A alternator charging, 400W of solar and full fusing. See the build →
- Expert build $6,587 A 400Ah bank, 800W of solar and a 3000VA inverter charger with shore power. See the build →
The one thing that has to be right
Twelve volts is low voltage and very high energy. A single 100Ah lithium battery will push several hundred amps into a short circuit, and undersized or unfused cable is one of the most common causes of fire in DIY vehicle builds. Every circuit on this site is fused at the source of power, within a few inches of the battery terminal, at or below the ampacity of the smallest conductor it protects.
Ampacity and voltage drop figures here follow ABYC E-11. Start with the ampacity chart, the fuse sizing chart and the wiring and fusing guide. This is researched guidance rather than an electrical certification, and a lithium installation should be inspected by a qualified installer before it carries load.
Gear, without the pretending
32 tiered gear guides and 16 build guides, all worked from published manufacturer specifications and verified owner reviews. We do not test gear in person and we never claim to.
Some products link to a scoped Amazon search rather than a product page. That is correct: Goal Zero, Battle Born, iKamper and much van-specific hardware sells direct or through dealers, and inventing a product code to make a card look complete would send you to the wrong thing.
Everything on the site
- Calculators, seven tools for sizing a 12V system
- Complete builds, three finished systems with totals
- Gear guides, tiered picks by category
- Build guides, how the system is planned and wired
- Comparisons, the decisions that shape a build
- Reference charts, ampacity, fusing and draw tables
- Power station specs, 36 units indexed
- About, who writes this and how
- Contact, corrections and enquiries