Headlamps, Batteries, Solar Charging, and Faraday Storage

What it's for

Light is the first thing you miss in an outage. This guide keeps your headlamps, lantern, radios, and phone going: how to store batteries so they're good when you grab them, how to use a power bank and a folding solar panel, and what a Faraday bag can and can't do.

Before you need it (practice)

• Standardize. Try to run everything on the same battery size (AA is common) and the same charging cable. The Prepared recommends it: fewer odd batteries, fewer cables.
• Learn your headlamp's modes in the dark at home (low, high, red) so you can find them by feel.
• Run the solar panel once on a sunny day. Charge the power bank from it and note roughly how long it takes on your panel.
• Test your Faraday bag (steps below) the day it arrives.

Step by step

Disposable batteries (alkaline)

Energizer's guidance:

1. Store in a cool, dry place at normal room temperature. The fridge or freezer isn't needed and can cause condensation.
2. Take batteries out of devices that'll sit unused a long time, or when they're dead.
3. Replace all batteries in a device at once. Don't mix old and new, brands, or types. Mixing can cause leaks or poor performance.

Rechargeables and power banks (lithium-ion)

1. For long storage, Battery University suggests keeping lithium-ion batteries partly charged (around 40%) in a cool, dry place, not full and not empty, and not freezing.
2. Top them up on a schedule. Check charge levels when you check the water, twice a year.
3. Charge rechargeable AA/AAAs in their matching charger only, per the maker.

Charging from a folding solar panel

1. Face it at the sun and keep it out of shade. Check your panel's manual for how it handles partial shade and clouds.
2. Charging a power bank from the panel lets you charge phones and radios from the bank after dark.
3. Follow your panel's manual for its ports and limits, and your phone maker's temperature limits.

Faraday bags and pouches

A Faraday bag is a shielded pouch that blocks radio signals when it's fully sealed. People use them to keep a phone or key fob from connecting, and to store spare electronics.

1. Test it: put a phone inside, seal it exactly per the instructions, and call it. If it rings, the seal or bag isn't doing the job.
2. Keep expectations honest. NIST's mobile forensics guidelines report that shielding containers don't always stop network communication, with text messages most often getting through, often due to weak shielding or leaks at the seal. An independent test of several bags found many failed to block cellular, Wi-Fi, or Bluetooth, and only one blocked all three reliably.
3. Store spares inside: a backup headlamp, a small radio, a USB drive with document scans.

Common mistakes

• Batteries left in a lantern for a year and leaking.
• Mixing a fresh battery with half-dead ones.
• Storing power banks dead (or in a hot truck all summer).
• One-of-a-kind chargers. If it needs a special cable, pack the cable with it.
• Trusting a Faraday bag you've never tested, or folding the seal wrong.
• Big promises. We don't claim any bag protects against specific events. Buy from a maker who publishes test data, and test it yourself.

Care & storage

• Twice a year: swap batteries, top up banks to partial charge, run every light for a minute, re-test the Faraday bag.
• Keep spares in the original packaging, or tape the contacts or bag each one, so they can't touch coins or keys and short out (Energizer).
• Keep a headlamp by each bed, with fresh batteries.

Related gear

• LED headlamp · Rechargeable LED headlamp · Headlamp with red light · Camp lantern
• AA/AAA batteries · Rechargeable AA/AAA + charger · Power bank · Foldable USB solar panel
• Faraday pouch · Faraday bag for spare electronics
• Category: Light & Power · Role: Lookout

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