Charging and storing LiPo safely: the rules you don't get to ignore

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Charging and storing LiPo safely: the rules you don't get to ignore

this is the one piece on this site where a mistake can cost you your house. so i'm not going to be cosy about it.

a LiPo that's mishandled can go into thermal runaway: a self-reinforcing reaction where the cell heats itself up, vents gas, and can catch fire. that kind of fire can't be put out with water and keeps going until the cell is spent. it's rare, but it happens, and almost always because of something that was preventable.

read this before you hang your first LiPo on the charger. it's ten minutes of your time. for lipo safe charging of airsoft batteries the rules aren't complicated, they just have to actually be followed.

the short version

always charge with a balance charger, via the balance plug
charge at 1C, not faster
charge in a LiPo bag or fireproof container, on a non-flammable surface
never leave a charging LiPo unattended
store at storage voltage, about 3.8 V per cell
never discharge below 3.0 V per cell, and keep to 3.3 V per cell in the field as a practical floor
a puffed, damaged or wet LiPo goes out of service immediately

the rest of this piece explains why.

voltage per cell: the numbers you have to know

a LiPo cell is 3.7 V nominal. that's the value on the label. in practice:

State	Voltage per cell
Fully charged	4.20 V
Storage voltage	about 3.80 V
Practical floor during use	3.30 V
Absolute minimum	3.00 V

for a 7.4 V pack (2 cells) that means: full 8.4 V, storage about 7.6 V, don't pull below 6.6 V.
for an 11.1 V pack (3 cells): full 12.6 V, storage about 11.4 V, don't pull below 9.9 V.

charging above 4.20 V per cell damages the cell and can make it vent. discharging below 3.00 V per cell damages the cell permanently, and recharging such a cell is dangerous. if a pack is genuinely deep-empty: don't charge it, dispose of it.

balance charging: why it's not optional

a LiPo pack is made of multiple cells in series. over their life those cells drift apart. one reaches 4.20 V while another sits at 4.05 V.

a simple charger only looks at the total voltage of the pack. it sees 8.4 V and thinks: done. while in reality one cell sits at 4.3 V and one at 4.1 V. that overcharged cell is exactly where it goes wrong.

a balance charger measures each cell separately through the small white balance plug and keeps them even. that's why you always connect both plugs: the thick power plug and the balance plug.

buy a decent charger. the IMAX B6 and similar are cheap and just do this properly. this is not the place to save fifteen euro.

charging at 1C

C is the capacity of the pack. a 1300 mAh pack you charge at 1C, so at 1.3 amps. a 2000 mAh pack at 2.0 A.

why not faster: a higher charge current means more heat and more stress in the cell. some packs claim they can take 2C or 3C charging. that can be technically true, and it still shortens the lifespan and raises the risk. there's no reason to rush for airsoft.

so set your charger to LiPo, the right cell count, and 1C. check the cell count before you start. charging a 2S pack on the 3S setting is one of the ways people genuinely cause fires.

where and how you charge

always:

in a LiPo-safe bag or a fireproof container (a metal ammo can, a ceramic plant pot, a tile with a stone container over it)
on a non-flammable surface: tile, concrete, metal
away from flammable material. not on the sofa, not on the carpet, not on a stack of paper
where you can be present and can see or smell it

never:

unattended. not even "just popping out for groceries". not overnight either. this is the rule that gets broken most and causes the most damage
in the car
on a pack that feels warm. let it cool to room temperature first
on a pack that's puffed, damaged, or has been slammed against something hard
at below-freezing temperatures. charging a LiPo below 0 degrees causes lithium plating and damages the cell

a LiPo bag is no guarantee that nothing happens. it's meant to contain a fire so you can do something about it, not to prevent it.

storage: the point everyone ignores

leaving a LiPo fully charged is the fastest way to wreck it. at 4.2 V per cell the chemistry is under strain and the cell degrades noticeably faster. leaving it empty is just as bad, because then it may drop below 3.0 V.

storage voltage is about 3.8 V per cell, roughly half of capacity. that's where the cell is chemically most stable.

every decent charger has a storage or storage charge function that brings the pack to that voltage, whether it's full or empty. use it.

when:

if your pack isn't used for more than about a week
always at the end of the season
after a playing day, if the next one isn't right around the corner

where:

cool and dry, room temperature or a bit colder
in a LiPo bag or fireproof container
not in the car, not in a shed that hits 45 degrees in summer, not in a damp garage
loose packs kept apart, not with the plugs touching each other

check your stored packs every few months with a cell checker (costs a few euro). if a pack has drifted down, charge it back to storage voltage.

in the field

don't run a pack down until your AEG stutters. that means you've gone too far. swap when you notice your rate of fire dropping
a LiPo alarm or low voltage buzzer on the balance plug costs a few euro and warns you. recommended
transport packs at storage voltage, not full
don't let packs roll around loose in a bag where they can be punctured or crushed. a mechanically damaged cell is the most common cause of a fire
don't store packs in the sun or in a car on a warm day

recognising when a pack is done

take out of service when:

puffing or swelling. this is gas forming in the cell. there is no "a little bit puffed". done, dispose of it
damaged outer layer, cuts, holes, dents
a cell that structurally lags behind during balancing
getting warm during normal use
a sweet or chemical smell
the pack has been wet

disposal

never bin a LiPo with your regular waste. that's exactly how bin lorries and sorting centres catch fire.

the right route: hand it in at a battery collection point (a recycling centre, hardware store, or electronics shop that takes batteries). many recycling centres have a separate bin for lithium batteries.

tape over the contacts before you take it in, so it can't short out.

about discharging in salt water that you'll come across online: that's now advised against, because it causes corrosion and gas formation and doesn't make the pack fully safe. just take it in.

if it does go wrong

if a pack starts to swell, hiss, smoke or smell during charging:

don't hang your face over it. the vapour is toxic
if it's safe: disconnect the charger from the mains
if it's safe: take the pack outside, to a spot with no flammable material, using something non-flammable (a metal shovel, tongs). don't do this with bare hands and not if it's already on fire
if it's on fire: don't try to put it out. get people away, close the door, call your local emergency number
put out surrounding material with water if you can, but don't count on putting out the cell itself

a small LiPo pack from an airsoft replica is considerably less bad than an e-bike battery, but it's more than enough to set a curtain or a sofa alight.

in summary

balance charger, 1C, in a bag, on stone, and stay with it. storage at 3.8 V per cell. puffed is gone. that's it.

if you take one thing from this whole article: never charge unattended. almost every LiPo fire story starts with "i'd just put it on the charger for a bit".

Sources

Also on Airsoft-FOB

also available in dutch: LiPo veilig laden en opslaan: de regels die je niet mag negeren

Jul 18, 2026 · 12:00· edited