Charge a LiPo battery on a balance-capable charger set to the correct cell count and a sensible current, never leave it charging unattended, and always charge it on a fireproof surface or in a LiPo-safe bag. Use a storage charge if the battery won't be run again within a few days, and retire (don't recharge) any battery that's puffy, punctured or damaged. None of this is complicated once you understand what each step is protecting against.
The reason all of this matters comes down to one underlying risk: a damaged or badly-treated lithium battery can enter what's called thermal runaway, where a cell heats itself faster than it can cool, feeding its own reaction until it vents or ignites. It's rare when a pack is treated properly, which is what the rules below are designed to keep true - none of this is about being alarmed by LiPo batteries, just about respecting what they are.
The golden rules
- Never charge a LiPo unattended - stay in the room, every time.
- Charge on a fireproof surface or inside a LiPo-safe bag, clear of anything flammable.
- Use a charger with a genuine balance-charging mode built for LiPo, not a basic NiMH-only charger.
- Match the charger's cell-count setting to the battery every single time - charging a 3S pack on a 2S setting (or vice versa) is a common, avoidable mistake.
- Storage-charge any battery that won't be used again within a few days.
- Retire a battery the moment it puffs up, gets punctured, or takes a hard hit - don't try to charge or discharge it further.
How to charge a LiPo correctly, step by step
Connect the main power lead first, then the balance lead - most modern chargers won't start a cycle at all if the balance lead is missing or on the wrong pins, which is a useful built-in safety check rather than a fault to work around.
Set the charger to LiPo mode, confirm the cell count matches what's printed on the battery (2S, 3S, 4S and so on), and set a charge current appropriate to the battery's capacity - a pack's manual or label will usually give a recommended rate, and charging well below that rate is always safer than guessing high. As a loose guide, charging at a rate equal to the battery's capacity in amp-hours (often written as '1C') is a safe, unremarkable default for most packs unless the manufacturer says otherwise.
Let a battery cool to roughly room temperature before charging it if it's just come off a run - charging a pack that's still warm from use, or one that's cold from sitting in a car overnight in winter, puts extra stress on the cells right when you want them behaving predictably. A few minutes' wait either way costs nothing.
Start the cycle and check on it periodically rather than treating the charger as fit-and-forget. A healthy pack charges without getting more than warm to the touch; a battery that's hot, swelling, or smells odd partway through a charge should be disconnected immediately rather than left to finish.
Make a habit of a quick visual check before every charge, not only after a crash: a look at the wrap for tears, the connector for discolouration, and the balance plug's pins for bent or corroded contacts takes only a few seconds and catches problems well before they reach the charger. A bent balance-plug pin is easy to miss and can cause a charger to misread individual cell voltages, so it's worth slowing down for a closer inspection if a pack has been dropped or knocked recently.
What is a storage charge, and when do you use it?
A storage charge brings a LiPo pack down (or up) to a resting voltage of roughly 3.8V per cell - noticeably below the 4.2V per cell of a full charge - which is the voltage LiPo chemistry sits at happiest over weeks or months of downtime. Sitting at a full charge holds the cells at their highest internal voltage stress for as long as they're left there, which is what accelerates ageing; sitting fully flat risks the cells drifting below a safe minimum voltage, which can make the pack unrecoverable. The 3.8V mark is the middle ground manufacturers settled on for that reason.
Most balance chargers built for LiPo include a dedicated storage mode that does this automatically - it'll charge a depleted pack up or bleed a full pack down to the target voltage and stop there. As a rule of thumb: if you know you're running a battery again within a day or two, a full charge is fine; if it's going in a drawer for a week or more - between weekend bashing sessions, or over a quieter winter stretch - storage-charge it first.
Charging safely: bags, surfaces and supervision
A dedicated LiPo-safe charging bag or fireproof charging sack is the standard, low-effort way to contain the rare thermal event - it won't stop a battery from failing, but it keeps a failure contained rather than spreading to whatever's nearby. Charge on a hard, non-flammable surface (tile, concrete, a metal tray) rather than on a carpet, a wooden bench, or a bed, and keep the setup clear of curtains, paper and anything else that burns easily.
Some hobbyists add a longer charge cable or extension lead as well, on the idea that it puts extra distance between them and the battery - but that isn't needed, and isn't something we'd recommend, once a LiPo bag is already part of the setup. The bag is what contains a failure, not the length of cable between charger and battery, so a longer lead just adds unnecessary resistance and another set of connections without any upside. Keep the charger's own cable and place the bag wherever's convenient and clear of flammables.
Supervision matters more than any bag or surface. A charger left running in another room, overnight, or while the house is empty removes the one safeguard that catches a problem early - noticing the smell, the swelling, or the heat before it becomes something worse. If a charge is going to run longer than you can reasonably stay nearby for, that's a sign to use a lower charge current instead of walking away.
The same rules apply away from home - charging between runs at a track or park from a car battery or a portable power pack. A charging bag still belongs under the setup, the charger still needs watching, and a car's own battery isn't bottomless - running it down too far charging packs can leave you without enough charge left to start the car afterwards, so keep an eye on that too if that's your power source for the day.
Signs a battery is done
A pack that's visibly puffed up, no longer sits flat, has a torn or punctured outer wrap with foil showing through, or came out of a hard crash should be retired - don't plug it into a charger again to 'see if it's fine', since a damaged cell can fail during that next charge. A pack that feels unusually warm before you've even connected it, or one where the connector housing looks melted or discoloured, belongs in the same category. Handle a suspect pack gently, keep it away from anything flammable, and treat it as done.
A battery that's over-discharged - run down further than it should have been, but otherwise undamaged - is a different situation and sometimes recoverable. We can attempt a recovery charge on an over-discharged pack sent in to us, though whether it comes back usable depends on how low it dropped and for how long. The best way to avoid needing that is the habit our team recommends: store batteries charged (or storage-charged) and unplugged between uses, rather than letting them sit flat.
How to dispose of a LiPo battery in NZ
Never put a LiPo battery, damaged or otherwise, in household rubbish or a standard kerbside recycling bin - lithium battery chemistry is a genuine fire risk once compromised, and general waste and recycling handling isn't built for that. For a battery that's reached the end of its life but isn't damaged, New Zealand has a growing network of battery recycling drop-off points - participating hardware stores, council transfer stations and community recycling hubs among them - so a local drop-off is usually the easiest option; check what's available in your area, since the network is still expanding rather than being one single nationwide scheme.
A swollen, punctured or otherwise damaged pack needs extra care before it even gets to a drop-off point: tape over the connector (and the balance plug, if separate) so it can't short against anything metal, place it in a fireproof or non-flammable container for transport, and take it to a facility set up for hazardous or e-waste rather than a general battery bin. If you're ever unsure whether a pack is safe to transport yourself, ask before you move it.
Choosing a charger that does this properly
The features that matter, in order: a genuine LiPo balance-charge mode (not just a NiMH charger with a LiPo label bolted on), a charge current you can set to match the battery rather than one fixed rate, and ideally a built-in storage-charge mode so you're not doing that calculation by hand. A basic manual balance charger - GT Power's SD4 is a straightforward, currently stocked example - covers all three for most single-battery setups without unnecessary complexity.
Multi-battery chargers and higher-end units add convenience (charging several packs in sequence or parallel, storing settings per battery type) but don't change any of the underlying safety rules above - the golden rules apply identically whether the charger cost a little or a lot. Browse our RC Batteries & Chargers range to compare what's currently in stock.
If you're weighing up battery types before you even get to charger choice - NiMH versus LiPo, what the C-rating numbers mean, which connector your car uses - we cover that in full in RC Battery Types Explained: NiMH vs LiPo, C-Ratings & Connectors.
FAQs
Can I charge a LiPo overnight?
No - never leave a LiPo charging unattended, including overnight. Modern chargers are reliable, but the entire point of supervision is catching the rare fault early, and a fault that develops while everyone's asleep has no one there to catch it.
What number do I charge at?
Match the cell count (2S, 3S, 4S) printed on the battery to the charger's setting, and set the charge current to what the battery's label or manual recommends - charging at a lower current than the maximum is always the safer default if you're unsure.
Why is my battery puffy?
Swelling means gas has built up inside the cells, usually from age, over-discharge, physical damage, or a charge that went wrong - it's a sign the internal chemistry has broken down, not something that settles back to normal. Retire a puffy pack rather than charging it again.
Can I use any charger?
No - a charger needs a genuine LiPo balance-charge mode to charge these packs safely. A NiMH-only charger, or a basic charger without balance capability, can overcharge individual cells within the pack even if the overall pack voltage looks fine, which is the kind of imbalance that leads to swelling or worse.
Ready to upgrade your charging setup? Browse our RC Batteries & Chargers range. If you're still finding your feet with your first car, start with Best Beginner RC Cars in NZ, or see What to Buy With Your First RC Car for the fuller shopping list. Questions? Message Us or visit us in Auckland.