Battery Audit: Know What You Have and Keep It Charged

Count every battery size your gear uses, keep coin cells away from kids, keep chargers and power banks topped up, and size a power station with simple watt-hour math.

Last updated 2026-11-039 official sourcesJump to sources

⚠ Coin and button batteries: keep them away from kids

Swallowed button batteries can cause severe injury fast. More than 3,500 people in the U.S. swallow them every year, and one stuck in the throat can do serious damage in as little as 2 hours.^[3]

Store new and used coin cells out of sight and reach of young children.^[4]
Tape shut any battery door a child could open, and tape used coin cells before you throw them out.^[4]
Be extra careful with any battery the size of a penny or larger.^[4]
If someone swallows one, call the National Battery Ingestion Hotline at 800-498-8666 or Poison Control at 1-800-222-1222 right away.^[3]

Flashlights, radios, smoke alarms, and phones all run on batteries when the power is out. Extra batteries and phone chargers are on the Red Cross list of basic emergency supplies.^[1] An audit tells you exactly which sizes you need so you're not guessing in the dark.

How much do I need?

Watts × hours = watt-hours.^[6] Example: a 10-watt LED lamp for 5 hours = 50 Wh. A 5-watt phone charge for 3 hours = 15 Wh. A 60-watt fan for 8 hours = 480 Wh. Total: 545 Wh for one day. Choose a power station with more than that, and multiply by the number of days you want to cover.

Take inventory

Walk through the house and list every device you'd want during an outage, and what it runs on.^[2]

AA and AAA: flashlights, headlamps, radios, remotes.
9-volt: many smoke alarms. Replace those batteries at least once a year.^[7]
CR123: some cameras and high-output flashlights.
Coin cells: key fobs, thermometers, scales. Store these safely (see the box above).
Rechargeables: plus a USB-C multi-bay charger, so one cable charges several.

Use flashlights, not candles, when the lights go out.^[8]

Phones, power banks, and jump starters

Keep a backup battery or another way to charge your phone.^[9]
Recharge power banks every time you test your smoke alarms, so they're full when you need them.
A portable jump starter is a battery pack that can start a car with a dead battery. Many can also charge a phone.
Store lithium-ion batteries (the rechargeable kind in phones, power banks, and power stations) at room temperature when possible, away from anything that can burn, and out of hot cars and direct sun.^[5]
Don't charge them below 32°F or above 105°F.^[5]
Stop using any battery that smells odd, changes color or shape, gets very hot, leaks, or makes noise. Recycle it; don't trash it.^[5]

Battery tenders for stored vehicles and equipment

A battery tender (also called a maintainer) is a small charger that keeps a parked vehicle's or generator's battery topped up without overcharging it. It's worth having for anything that sits for weeks, like a backup car, a riding mower, or an electric-start generator.

Plug it in whenever the equipment will sit for more than a few weeks.
In flood-prone areas, disconnect vehicle batteries if flooding is expected.^[8]

Solar panels and portable power stations

A portable power station is a big rechargeable battery with outlets and USB ports. Its size is listed in watt-hours (Wh). Solar panels can recharge it during the day.

The math: energy used = power × time. Multiply a device's watts by the hours you'll run it to get watt-hours.^[6]
The wattage on a label is the most a device draws, not what it always uses, so real use is often lower.^[6]
Add up the watt-hours for everything you'll run and pick a station with more capacity than that total.

Checklist

List every emergency device and the battery size it uses
Stock spare AA, AAA, 9-volt, CR123, and coin cells you actually need
Lock coin cells away from children
Replace smoke alarm 9-volt batteries once a year
Get a USB-C multi-charger for rechargeables
Recharge power banks and the jump starter when you test smoke alarms
Put a battery tender on vehicles or equipment that sit
Store lithium-ion batteries away from heat and anything that burns
Write the purchase date on battery packs and use oldest first

Mistakes to avoid

Leaving coin cells loose in a drawer kids can reach
Buying a big pack of a battery size you don't use
Letting power banks sit uncharged for a year
Keeping lithium-ion batteries in a hot car
Using candles instead of flashlights
Throwing swollen or leaking lithium-ion batteries in the trash

Do this this weekend

Gather every flashlight, radio, and battery-powered device into one spot. Test each one, write down the battery sizes on a single list, and tape it inside your kit lid. Move all coin cells to a high, closed container.^[4]

Gear that helps

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Batteries and USB-C chargersRechargeable AA/AAA batteriesRechargeables plus a charger mean you aren't relying only on what's in the drawer.Check it (opens retailer site)
Batteries and USB-C chargersUSB-C multi-battery chargerCharges AA and AAA batteries from a power bank or solar panel when the grid is down.Check it (opens retailer site)
Power banks and solar stationsHigh-capacity power bankSeveral phone charges in your pocket; keep it topped up.Check it (opens retailer site)
Power banks and solar stationsPortable power stationQuiet, fume-free battery power you can use indoors for phones, lights, CPAP or a small fridge.Check it (opens retailer site)
Battery tendersBattery tender / maintainerKeeps stored vehicle, generator and mower batteries charged so they start when needed.Check it (opens retailer site)
Jump startersPortable lithium jump starterStarts a dead car without a second vehicle, and most double as a phone charger.Check it (opens retailer site)

See all gear by category

Sources

Survival Kit Supplies Red Cross
Power Outage Safety Red Cross
Swallowed a Button Battery? National Capital Poison Center (Poison Control)
Batteries Cause Devastating Injuries National Capital Poison Center (Poison Control)
Battery Fire Safety US Fire Administration
Watt Does It Cost to Use It? DOE Office of Energy Efficiency and Renewable Energy
Smoke Alarms US Fire Administration
Severe Weather Fire Safety US Fire Administration
Winter Storm Safety Red Cross

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