Energy plan for emergency communication: batteries, cold, reserve

A battery stores energy chemically. In the cold these chemical processes slow down and the battery can temporarily deliver less power. That is why a phone sometimes shuts down in frost even though the display showed a fair amount of charge a moment ago. Once the battery warms up again, part of that charge is often usable again.

The biggest power consumers in a smartphone are the screen, the radio connections and continuous GPS logging. Searching for a network with poor reception is especially costly: the phone then transmits at higher power and keeps trying again and again. In a valley without signal a battery can run down surprisingly fast this way.

Switching off these consumers deliberately and using devices to a plan rather than casually extends run time considerably. It costs nothing but a little discipline.

Start fully charged: charge phone, lamp, GPS, satellite device and power banks the evening before. Check spare batteries and pack the right cables – a wrong or missing cable makes the best power bank useless. Make a small list of which device needs which battery or cells.

On the way: power-saving mode on, screen brightness down, Bluetooth, Wi-Fi and background apps off when you do not need them. Download maps for offline use beforehand instead of loading them over the network on the way. Photos and videos make nice memories, but they cost power you may still need.

Where there is no signal, airplane mode pays off. Then switch the phone on briefly at fixed times to check messages. This works best when a contact knows these times and knows when they can reach you.

The heart of the energy plan is a fixed reserve used only for emergency calls, location and contact with rescuers. This can be a separate power bank that you do not touch on the way, or a minimum phone charge level that you do not go below for photos or music. Set this limit beforehand, not when the battery is already low.

Why so strict? Because emergencies do not announce themselves. If you only notice things are serious when the battery is almost flat, you may have no power left for the call, for being located by the dispatch centre or for the rescuers' callback. The callback in particular is often underestimated: rescuers want to ask questions, give advice or guide you.

For devices with replaceable batteries, such as many headlamps, carry matching spare batteries in your pack – packed dry.

Lithium batteries are built into phones, power banks and many lamps. They are very practical, but a damaged, swollen or unusually hot battery can catch fire. Do not keep using or charging such a battery, and dispose of it properly later.

Keeping batteries warm does not mean making them hot. Carry the phone and spare batteries close to your body in an inner pocket and take them into your sleeping bag at night. But if a device gets hot while charging in the sleeping bag, take it out – heat under an insulating cover is dangerous.

An energy plan does not replace signalling tools that work without power. A whistle and a signal mirror need no battery and still belong in your kit.

Multi-day trip: here it pays to check consumption on the first evening. How much battery is left? Will it last if you carry on like this? If not, start saving more right away. Solar chargers can help on long trips but often deliver little in cloud, forest and winter – plan them as an extra at most.

Winter trip: cold is the biggest enemy. The phone does not belong in the outer pocket of your pack or jacket but close to your body. If a cold device has shut down, warm it up in an inner pocket first before switching it on again.

Power cut at home: the same rules apply. Keep power banks charged, use a battery radio for news and use the phone only for important contacts. Agree within the family who calls when, so that not all batteries run flat at the same time.