Short answer: three months unused is not a problem as long as you store the pack at 40–60% charge, in a cool, dry place, with the contacts protected from shorting. A healthy LP-E6NH will not swell simply because it sat in a drawer for three months. Swelling comes from long periods at full charge combined with heat, from overcharging or over-discharging, or from physical damage — it is an issue of how the pack is used and stored, not of elapsed time.
Many people put a battery away fully charged, thinking it will be ready to use next time. That is exactly the wrong state for storage. At a high state of charge the cathode sits at a higher potential and electrolyte side reactions are more active; add the heat of a summer drawer and aging runs noticeably faster than at half charge. Three months is unlikely to cause a failure, but repeating it for three or four months every year adds up.
1. Three parameters — charge, temperature, humidity
Charge level matters most. Too high accelerates side reactions; too low risks self-discharge pushing the pack into over-discharge, which can cause irreversible capacity loss or leave it unable to charge. 40–60% covers both ends, and most manufacturers’ long-term storage guidance lands in that range. Lithium-ion self-discharge is typically in the single digits per month, so three months costs little and there is no need to worry about it running flat.
Temperature is the most underestimated factor. Aging rate is quite sensitive to heat; stored above 30°C, capacity loss runs clearly faster than at around 20°C. So keep packs out of balcony cabinets, cars, and spots near radiators or routers that stay warm.
Humidity mainly affects the contacts and the protection board. In damp conditions metal contacts oxidize, which shows up as poor contact and camera errors. A desiccant packet or a dry box is a cheap and effective measure, but you do not need lens-grade rigor.
2. Four steps before storage
- Confirm the charge level. Put the pack in the body and check the percentage. Above 70%, shoot down to about 50% before taking it out; below 30%, charge it to 50% first. Do not top it off “so it keeps longer.”
- Clean the contacts. Wipe the metal contacts with a dry, lint-free cloth to remove fingerprints and dust. Do not flood them with alcohol, and do not scrape them.
- Store packs separately. Put each pack in a terminal cover or its own small pouch so it cannot sit against other packs, keys or coins and short its contacts. This matters more than many people expect — a short can generate a great deal of heat in seconds.
- Pick the spot. A cool, dry, dark drawer or cabinet with a stable temperature, away from heat sources and water. One desiccant packet is enough.
Three months needs no top-up in between. If you are storing for more than six months, check the charge every four to six months and bring anything below 30% back to about 50%. The purpose is to prevent over-discharge, not to “reactivate” the pack.
3. What causes swelling, and three checks you can do
| Cause | Mechanism | Typical scenario |
|---|---|---|
| Long storage at full charge plus heat | Electrolyte decomposes and generates gas at high potential, raising internal pressure | A full pack in a sun-baked car or a summer drawer |
| Overcharging | A faulty or non-compliant charger pushes voltage past the limit | No-name chargers, packs with no protection board |
| Over-discharging | Forcing a charge into a deeply discharged pack damages the internal structure and generates gas | Fast-charging a pack that sat flat for months |
| Physical damage | A drop or a crush damages the internal separator | A pack falling out of a bag onto hard ground |
Note that “sitting unused” is not on that list. The combination worth watching is full charge plus heat, which is also the most common everyday situation.
The flat-surface test. Put the pack on a level surface (glass or marble is best), press one corner lightly and release. Does it rock like a spinning top? A slight rock can be case tolerance; a clear wobble is a warning.
Sight along the side in the light. Stand the pack on its side and check whether the case seam has opened or the sides bulge in a symmetrical arc. A healthy LP-E6NH should have flat, straight sides.
How it feels going in. If it goes into the body or the charger noticeably tighter, needs force, or the latch will not seat, the shape has already changed — do not force it and risk jamming it in the compartment. Of the three checks this is the most direct and reliable: if one is questionable and the other two are fine, keep watching; if two or more are off, retire the pack.
4. The first use after storage
After three months, check the charge level before deciding whether to charge rather than dropping it straight onto the dock. If it reads zero or the body does not recognize it at all, do not force a charge — that may be over-discharge, and pushing current into it carries risk. Treat it as end-of-life instead. If the level is in the normal range, one or two ordinary charge-discharge cycles bring it back; no special “activation” routine is needed.
Also, before the first demanding shoot after long storage, run one light-load full cycle and watch for unusual heat or sudden jumps on the gauge. It amounts to a cheap check-up.
For compatibility and recognition differences across generations, see the LP-E6NH category and the LP-E6 category. If you also shoot in the cold, the general conclusions in battery behavior at low temperatures apply to how temperature affects usable capacity. The same storage rules apply to YO’s LP-E6NH-compatible packs — leave them at about half charge before putting them away. One naming note: LP-E6+ is not a Canon designation, it is how some third parties label an enhanced pack, so follow the cell chemistry rather than the label.
FAQ
Is it okay to leave a battery in the camera for three months?
Not recommended. A body on standby draws a small current continuously, which over months can pull the pack into over-discharge, and the space inside a body is tight and vents poorly. Taking it out and storing it separately is safer.
It has swollen slightly — can I still use it?
No. Swelling means gas has formed inside and structural integrity is reduced. Continuing to charge and discharge it is a safety risk, and it may jam in the body. Dispose of it under local e-waste rules rather than in household trash.
Is the refrigerator a better place to store it?
Not recommended. A household fridge is humid, and condensation forms when you take the pack out, which is hard on the contacts and the protection board. Very low temperatures also affect the electrolyte. A cool, dry room is enough; there is no need to chill it deliberately.
Capacity dropped after long storage — is the pack failing?
Not necessarily. Some capacity loss is recoverable and comes back after a few normal cycles. Only if it stays clearly below the pre-storage level after several full cycles has irreversible degradation set in. That judgment needs a baseline, so record runtime before you put a pack away.