Short answer: before an outage, choose one cool, dry storage spot, charge each device only with the charger made or approved for it, and inspect every backup battery for the warning signs fire-safety guidance lists: extreme heat, swelling, hissing or popping, unusual odors, and smoke. Also look for cracked cases. If a battery shows any of these, do not use it. The decision tree below shows what to do at each level.
By InfinitePowerSolutions.com Technology Desk. Written September 30, 2026. General safety information, not professional advice. We did not test any batteries for this article; every safety point comes from the sources listed at the end.
What This Guide Covers and What It Does Not
This guide covers care and inspection of consumer rechargeable backup batteries. The safety guidance we relied on is written for lithium-ion batteries, which it names in phones, laptops, power tools, and e-bikes. If your backup battery is lithium-ion (check the label or manual), the same cautions apply. It does not cover other battery types or whole-home battery systems wired in by an installer. For your specific device, the manufacturer's manual comes first.
This is different from a runtime calculation. To work out how long a portable power station can run your devices, use our room-by-room runtime worksheet. This page is about whether the battery is safe to keep, charge, and rely on.
Step 1: Choose a Storage Spot
- Store devices and batteries in a cool, dry place, out of direct sunlight (New York State consumer safety guide).
- Keep them away from extremely high or low temperatures. The same guide says not to charge them below 32°F (0°C) or above 105°F.
- A 2016 Massachusetts State Fire Marshal memo adds that cold can keep a battery from holding a charge, while high temperatures or prolonged sunlight can cause a malfunction that leads to fire.
- Store and charge according to the manufacturer's instructions, and do not disassemble or modify a battery.
A hot garage, a parked car in summer, or a sunny windowsill do not meet “cool and out of direct sunlight.” Judge the spot by its worst day, not a mild one.
Step 2: Set Charging Rules Before You Need Them
- Use the right charger. The state guide says to use the charger that came with the device, or a replacement approved by the device manufacturer. A charger that fits the port is not necessarily safe for the battery.
- Do not leave charging batteries unattended. The guide warns that unattended charging can increase the chance of overcharging, and says not to leave devices charging while you sleep.
- Plug into a wall outlet. The state guide and the U.S. Fire Administration both say to avoid power strips and multiplug adapters, which can overheat. The USFA also says not to charge through extension cords.
- Pick the surface and spot with care. For phones, laptops, and similar devices, the state guide says to avoid charging under a pillow or on a bed or couch, and the Massachusetts memo says heat can get trapped on soft or combustible surfaces. For e-bikes, scooters, and hoverboards, the guide says to charge in a flat, dry area away from children, direct sunlight, liquids, and tripping hazards, and not near the front door, where a fire could block your exit.
- Remove devices once fully charged.
If you are unsure whether your outlets and circuits suit your charging setup, the USFA says to have a professionally licensed electrician test them.
Step 3: Run a Simple Inspection Routine
The sources say to inspect “regularly” but set no schedule. Choose one you will keep, such as the start of each season, and check every backup battery and its charger:
- Look for broken or cracked cases.
- Look for swelling, bulging, lumps, or leakage.
- Note any strong or unusual odor.
- Note whether the battery feels extremely hot. The state guide says some warmth during charging or use is normal, but extreme heat suggests a defect.
- Listen for hissing, cracking, or popping.
- Confirm the charger is the one that came with the device or one the manufacturer approves.
- Our suggestion, beyond what the sources say: search the product name at cpsc.gov/Recalls. The state guide recommends checking recalls before buying, and rechecking batteries you already own is a reasonable extension.
When shopping, the state guide also suggests buying from reputable manufacturers and looking for a safety mark from a nationally recognized certification laboratory, such as Underwriters Laboratories.
Damage-Escalation Decision Tree
Work through the questions in order and stop at the first “yes.”
Question 1: Is there smoke, fire, or flames?
- Yes: Leave the area immediately and call 9-1-1. If you cannot get outside, call 9-1-1 and tell the fire department you cannot get outside.
- Do not try to put the fire out yourself. The state guide says lithium-ion battery fires spread quickly, can become explosive or reignite, water may not stop them, and fire extinguishers do not work on them.
- No: Go to Question 2.
Question 2: Does the battery show a warning sign?
The state guide lists these: it feels extremely hot, it is swelling, bulging, or leaking, it makes hissing, cracking, or popping sounds, or it gives off a strong or unusual odor. The guide also notes that failing lithium-ion batteries emit toxic fumes.
- Yes: Stop using the device and turn it off. Unplug it from the power source. If it is safe to do so, move it away from anything flammable using tongs or gloves. Leave the area and call 9-1-1, as the guide directs.
- No: Go to Question 3.
Question 3: Is the case cracked or broken, with no other warning sign?
- Yes: Treat the battery as damaged. The state guide says damaged batteries have a greater risk of thermal runaway fires, and the Massachusetts memo says to replace and properly discard damaged batteries. Do not charge or use it, and do not open or modify it. The USFA says repairs to lithium-ion battery packs should be done only by a certified repair facility. The sources do not say who to call about a cracked case; the manufacturer's manual or support line is a sensible place to start. See the disposal section below.
- No: Go to Question 4.
Question 4: Is the product on the recall list?
- Yes: Follow the instructions in the recall notice. The state guide lists recalled batteries among those that need specialty handling for disposal (see below).
- No: Go to Question 5.
Question 5: Is the charger the one made or approved for this device?
- No or unsure: Replace it with one the device manufacturer approves before the next charge.
- Yes: This check found no problem. That is not a guarantee, so repeat it on your schedule and return the battery to its storage spot.
Disposing of a Battery You No Longer Trust
- Never put lithium-ion batteries in household trash or recycling bins, according to the state guide. The USFA gives the same warning because they can ignite.
- The USFA advises taping over battery ends and terminals to help prevent accidental discharge, and checking with local authorities about collection sites.
- For non-vehicle rechargeable batteries under 25 pounds that are in good condition, the state guide points to the Call2Recycle retail takeback program. For damaged, defective, or recalled batteries, it says Call2Recycle sells specialty kits for handling them safely.
When to Get Professional Help
- Fire department (9-1-1): any smoke or fire, and the warning signs in Question 2.
- Certified repair facility: any repair of a lithium-ion battery pack. Do not open or modify a battery yourself.
- Licensed electrician: if you are unsure your outlets or circuits suit your charging setup.
- Installer: a battery system wired into your home is outside the scope of this guide.
What to Do Next
You can finish the basics in one sitting without buying anything: gather your backup batteries, run the inspection list, fix your storage spot, and confirm each charger is the right one. Then continue your outage planning:
- Portable Power Station Runtime: A Room-by-Room Outage Planning Worksheet
- Power Station Labels: Watt-Hours, Watts, and Runtime Estimates Explained
- Home Wi-Fi During an Outage: Router, Modem, and Backup-Power Planning
Sources
- New York State Division of Homeland Security and Emergency Services and Department of State, Lithium-Ion Battery: A Consumer Safety Guide (storage, temperature limits, charging, warning signs, fire response, disposal, recall check before buying).
- U.S. Fire Administration, Fire Prevention and Community Risk Reduction (charging, outlets, electrician testing, repairs, disposal).
- Massachusetts State Fire Marshal, Lithium-ion Battery/Hoverboard Safety, memo dated April 4, 2016 (temperature effects, soft surfaces, replacing damaged batteries). This is an older memo written mainly about hoverboards.
- U.S. Consumer Product Safety Commission, Recalls, the recall database named in the New York guide.
Disclosure: this article contains no affiliate links and does not recommend a product. Safety guidance changes, so follow your device manufacturer's instructions and local fire authority over anything here.
