Portable Power

Start by counting the electricity you actually need

Choosing a portable power station by capacity (Wh) alone leads to mistakes. First write down the power draw (W) of each device and how long you will use it. Multiply watts by hours and you have a rough figure in Wh. A 10 W light used for 5 hours needs about 50 Wh.

You cannot use all of the stated capacity, because conversion losses reduce what you actually get. Pick something with some margin over your calculation. Heat-producing appliances such as electric kettles, hair dryers and heaters draw a lot of power and quickly exceed both capacity and output. Plan on leaving them at home and the size you need stays reasonable.

Do you need a power station at all?

If you only need to charge a phone and run a light, a mobile battery and a battery-powered LED light may be enough. A power station makes sense when you run something all night, such as a fan or an electric blanket, or when several people share devices. Decide from the total draw of your devices and the number of nights.

Points to compare

Compare the manufacturer's stated figures on these points, and confirm the numbers in the seller's or maker's current information.

• Capacity (Wh): is it enough for your devices and nights?
• Rated output (W): is there margin over the total of devices run at once?
• Weight and handle: can you carry it from the parking area to your site?
• Output ports: do the USB, AC and car-socket outputs match your devices?
• How it charges: wall outlet, car or solar. Solar varies greatly with weather and sunlight, so treat it as a supplement
• Operating temperature range: does it work in summer heat and winter cold?
• Warranty and a support contact

Safety: heat and where you put it

Power stations get warm during use and charging. Do not leave one in direct sunlight or in a closed car in summer. Keep the vents clear, and do not cover it with cloth or luggage. Keep it off bare ground and away from rain, condensation and damp, and put it somewhere dry.

If the case swells, smells odd, runs unusually hot or is deformed, stop using it and contact the manufacturer. Follow your local authority's rules for disposal and do not simply throw it away. Engine generators produce carbon monoxide and noise, and some sites ban them or do not allow them near tents and cars. Ask the site.

Plugging several devices into an extension cord can exceed its rating. Stay within the stated output.

Cautions specific to free and low-cost campsites

Where there is no power you cannot recharge on site. Charge fully before leaving, and prioritize low-draw devices such as lights. Even where power is offered, limits on devices, fees and hours differ by site, so read the notice beforehand.

Do not leave expensive equipment unattended at an unstaffed site. When you leave your car or tent, keep it out of sight.

Common mistakes

Looking only at capacity and having too little output to run a device. Buying something too heavy to carry to the site. Forgetting to charge at home. Leaving it in a hot car so it overheats. Buying without knowing the draw of your devices. A little calculation and checking beforehand avoids all five.