Water, Power and the Waste Nobody Plans For

The point of a travel vehicle is the number of days it can stay away from infrastructure. That number is set by whichever runs out first: water, electricity, food or the ability to deal with waste. Building for autonomy means finding the shortest of those and lengthening it, then finding the next.

Water: how much, and where

Plan five litres per person per day for drinking, cooking and minimal washing in moderate conditions, eight to ten in heat. For two people wanting a week of autonomy that is 70 to 140 litres, which is 70 to 140 kilograms, and immediately a payload question rather than a plumbing one.

Split the capacity. Two tanks, or a tank plus containers, means a leak or a contamination event does not empty the trip. Keep the main tank low and between the axles, because water is the densest thing you carry and its position affects handling more than anything except fuel.

Treat what you take on rather than trusting the source. A sensible chain is a coarse pre-filter when filling, a pump or gravity filter capable of removing bacteria and protozoa for drinking water, and chemical treatment as a backup. In regions with viral risk, add a purifier rated for viruses or boil. Clean the tank properly every few months and keep a dedicated food-grade hose, coiled in its own bag, never on the ground.

Power: start from the fridge

In almost every travel vehicle, the fridge is the load that sets the system. A good compressor fridge draws roughly 30 to 60 amp hours a day in warm conditions, more if it is opened often or sits in the sun. Lights, phones, a laptop and a water pump add perhaps 15 to 25. So a realistic daily budget is 50 to 90 amp hours.

The battery then needs to store two to three days of that without deep discharge, which means 100 to 200 amp hours of lithium, or twice that in lead acid, because lead acid should not be taken below half. Lithium is lighter, tolerates deep discharge, lasts far longer and costs more, and for most builds it now works out cheaper per usable amp hour over the life of the trip. It does need protection from charging below freezing, which matters in winter travel.

Autonomy is not a feature you buy. It is the smallest of your three tanks: water, power and patience.

Charging, in three ways

• From the engine: a battery-to-battery charger is the reliable backbone. An hour of driving replaces a substantial part of a day's use, which is why vehicles that move regularly rarely have power problems.
• Solar: 200 to 400 watts on the roof covers a fridge in summer and contributes usefully in winter. It is the system that lets you stay still for a week, which is precisely what most travellers end up wanting.
• Mains: a small charger for the occasional campsite or workshop stop. Cheap, light, and the thing that saves you after three grey days.

Isolate the living system from the starting battery, always, with a proper relay or DC-DC unit. The one electrical failure that must never happen is being unable to start the engine because the fridge ran all night.

Build it so it can be diagnosed

Fuse everything, close to the source. Label both ends of every cable. Use a shunt-based monitor so you can see amp hours in and out rather than guessing from a voltage reading. Keep a wiring diagram in the vehicle, on paper. When something fails at nine at night in the rain, the difference between a twenty minute fix and a ruined week is whether you can trace the circuit.

Waste, the part nobody photographs

Grey water from washing up contains fat and food and should not go on the ground at a camp, particularly at a popular one. A tank or a container, emptied at a proper disposal point, is the responsible answer, and increasingly the legally required one in Europe. Black water, if you carry a toilet, needs a chemical or dry system and a plan for disposal that is not a hedge; dry separating toilets have become popular precisely because they solve this without chemicals.

Rubbish is the other half. In many regions there is no collection at all, so plan to carry compacted waste for days, keep it sealed, and never leave it at a village bin that is already overflowing.

Questions we get asked

How much solar do I need?

For a fridge plus normal small loads, 200 watts is a working minimum and 300 to 400 gives you margin in poor weather and winter sun. Panel angle and shade matter as much as capacity: a partly shaded panel can lose most of its output.

Lithium or lead acid?

Lithium for weight, usable capacity and lifespan, which suits nearly every travel build. Lead acid remains defensible where budget is tight, weight is not, or the vehicle will sit in deep cold and charging below freezing is a real risk.

Do I need a water pump?

A foot pump or a simple electric pump with a tap is enough for most builds and fails less often than a pressurised system. Whatever you fit, keep a way of drawing water directly from the tank when the pump dies.