How many spare POC batteries can I bring on a plane?

For batteries under 100 Wh (which covers most Inogen and OxyGo single and double batteries), the FAA sets no numerical limit—but you must be able to physically carry them. Use the 150% rule based on your total transit time to determine the exact number you need.

Can POC batteries go in checked luggage?

No. All spare lithium-ion batteries must be in your carry-on baggage. Only the battery currently installed in the device may be in checked luggage (inside the device). This rule is non-negotiable under FAA Advisory Circular AC 120-76E.

What charge level should I store a tool battery at?

Around 40–50% (some sources say up to 60%). This is the low-stress 'Goldilocks zone' — it's high enough to avoid a damaging deep discharge from self-discharge over months, and low enough to avoid the high-voltage stress of sitting at 100%.

Is it bad to leave a tool battery on the charger all winter?

Yes — storing at a constant 100% accelerates capacity loss, especially if it's warm. For long storage, take it off the charger at about 40–50% and check it every month or two instead.

What temperature is best for storing lithium batteries?

A cool, dry, stable spot, roughly 10–25°C (50–77°F). Heat is the bigger enemy: stored at about 40°C a battery may retain only ~85% capacity after a year, versus ~96% at 25°C. Avoid hot sheds, cars, and freezing garages.

My battery won't charge after winter storage. Is it dead?

If it fell into deep discharge, the BMS may have locked it out. Some chargers can slowly revive it over a long, supervised charge. If there's no response, or it shows swelling, it has likely degraded and needs replacing.

How to Store Power Tool & Mower Batteries Over the Off-Season

June 1, 2026 Cao Chuanping

The Ultimate Guide to Storing Your Power Tool & Mower Batteries

When mowing season ends, it's tempting to toss the mower and drill in the shed and forget them until spring. But for lithium-ion batteries, neglect over the off-season is the fastest way to ruin them — and few things are more annoying than reaching for a tool months later to find the pack dead and refusing to charge. A few minutes of the right prep protects packs that can cost $80–200 to replace.

Why temperature and charge level matter

Lithium-ion packs are light and powerful, but chemically sensitive: the reactions that store and release energy are affected by both temperature and state of charge. Get those two right in storage and the battery barely ages; get them wrong and it degrades even while sitting idle.

Temperature

How storage temperature affects lithium-ion cells.
Temperature	Effect
Below 0°C (32°F)	Electrolyte thickens, resistance rises. Never charge here — it can cause permanent lithium plating.
0–10°C (32–50°F)	Reduced performance but safe for storage. Avoid charging.
10–25°C (50–77°F)	Ideal storage range — minimal degradation.
25–35°C (77–95°F)	Aging accelerates noticeably the warmer it gets.
Above 35°C (95°F)	Real risk of electrolyte breakdown, swelling, and permanent capacity loss.

Heat is the bigger enemy, and the numbers are stark: stored at about 40°C (104°F), a lithium battery may retain only around 85% of its capacity after a year, versus roughly 96% at 25°C (77°F). A fully charged pack left somewhere hot fares worse still.

State of charge

0%
deep-discharge risk 40–50%
store here 100% — high-voltage stress

EmptyFull

Sitting at 100% keeps the cell under high-voltage stress, so the electrolyte breaks down faster and swelling risk rises. Sitting at 0% is just as bad: over months, self-discharge can drop a cell into deep discharge (below roughly 2.5V per cell), which can be irreversible — the pack may refuse to charge again.

The Goldilocks zone: about 40–50% charge at a cool room temperature. As Battery University notes, the exact percentage isn't critical — 40–50% is the target, not a precise setpoint.

Storing them, step by step

Set the charge to 40–50%

If it's full, run the tool lightly until the gauge shows about 2 of 5 lights. If it's low, charge it just up to the 40–50% band — don't top it to 100% for storage.
Clean the contacts

Wipe the battery terminals and the tool's connector with a dry cloth to clear dust and corrosion. No water or solvents unless the maker specifies it. Dirty contacts cause resistance and charging errors later.
Pick the right spot

Aim for somewhere temperature-stable, dry, and ventilated. See the table below for the ranking.
Keep humidity and sun off it

Keep humidity below ~65% (moisture corrodes contacts and seeps into casings), and out of direct sun, which heats the pack and degrades the housing.
Check every 1–2 months

Even in ideal storage, packs self-discharge slowly. Every 4–6 weeks, check the gauge; if it's below 30%, top back up to ~50%. Inspect for swelling, cracks, or corrosion while you're at it.

Where to store — ranked.
Location	Rating	Notes
Inside the home (closet, conditioned basement)	Best	Stable 15–25°C
Insulated, attached garage	OK	Only if it stays above 0°C and below ~30°C
Uninsulated shed	Avoid	Bakes in summer, freezes in winter
Car or truck	Never	Temperature extremes and vibration

Waking them up in spring

When the season returns, bring packs back gently rather than slapping them straight onto a hard job:

Charge on the original charger. Let it come up to a full charge on the maker's charger (or an approved replacement) — a generic charger may not communicate properly with the BMS.
Watch the first charge. The pack should feel slightly warm, not hot. If it gets uncomfortably hot or the charger flashes an error, stop and check the manual.
Then just use it normally. Run the tool or mower through ordinary work; the gauge re-syncs on its own as you use it. You don't need to force a deliberate deep discharge to "recalibrate" — for modern lithium-ion, that adds unnecessary stress.
Confirm it performs. Runtime roughly matches what you'd expect, no surprise shutdowns, no overheating. If performance is clearly poor, the pack may have degraded in storage and need replacing.

Common mistakes to avoid

Mistake	Why it hurts
Storing full on a hot garage floor	Heat + high voltage = accelerated aging and swelling risk
Storing it dead-flat	Deep discharge can permanently lock the pack out via the BMS
Leaving the battery on the tool	Some tools draw a tiny parasitic current that slowly drains it too low
Storing beside lawn chemicals	Corrosive fumes attack contacts and seals
Forgetting to check for months	Self-discharge can take it below safe voltage

The golden rules

Store at 40–50% charge, never full or dead-flat
Keep it cool, dry, and stable (10–25°C / 50–77°F)
Check every 1–2 months and top up to ~50% if needed
Wake it gradually, then just use it normally
Never store in a hot shed, a car, or a freezing garage

Heading into a new season and a pack won't hold up? We carry replacement lithium-ion batteries for mowers, power tools, and cordless gear — Grade A cells, full BMS protection, 1-year warranty. Browse the power tool battery collection, or for EGO mowers see our EGO 56V battery guide.

Frequently asked questions

What charge level should I store at?

About 40–50% (up to 60% is fine). High enough to avoid a deep discharge over months, low enough to skip the high-voltage stress of sitting at 100%.

Is leaving it on the charger all winter bad?

Yes — a constant 100% accelerates capacity loss, more so if warm. Take it off at ~40–50% and check every month or two.

Best storage temperature?

Cool, dry, stable — roughly 10–25°C. Stored near 40°C a pack may keep only ~85% capacity after a year vs ~96% at 25°C. Avoid hot sheds, cars, and freezing garages.

It won't charge after winter — is it dead?

If it deep-discharged, the BMS may have locked it. A long, supervised charge sometimes revives it; if there's no response or it's swollen, it likely needs replacing.

References

Battery University, BU-702: How to Store Batteries (Cadex Electronics).
Battery University, BU-410: Charging at High and Low Temperatures.
Manufacturer storage guidance (e.g. EGO Power+, DeWalt, Milwaukee owner's manuals).

Back to blog