LiPos › Charging LiPo batteries safely, and why balance charging matters
Charging LiPo batteries safely, and why balance charging matters
Most LiPo fires start during charging. These are the settings and habits that cut the risk.
Use the right charger
Use a charger designed for LiPo batteries and check it is on the LiPo setting. Fire services warn against fake or cheap chargers and advise using the manufacturer's recommended charger from a reputable source. Do not use a charger set for a different chemistry.
What balance charging does
A multi-cell pack has several cells in series. They do not stay perfectly equal, so one cell can end up higher than the rest. A balance charger monitors each cell through the small balance lead and tops them up evenly so no cell goes over 4.2 V. BYU's guide says to use the Balance Charge setting, not plain Charge, and to select LiPo and the correct cell count (for example 3S for a three-cell pack).
Charge settings
- Chemistry: LiPo.
- Cell count: match the pack (2S, 3S, 4S...). Check it on the charger before you start. A wrong cell count is a common cause of overcharge.
- Current: set from capacity. As an example, a 500 mAh battery charges at 0.5 A. Do not exceed the maker's recommended rate.
- Cut-off: a LiPo should not be charged above 4.2 V per cell or below 3.0 V per cell, according to BYU.
Charging habits
- Check the pack first. Look for swelling, dents, cuts or damaged leads. West Yorkshire Fire and Rescue advises checking for damage before every charge. Never charge a damaged pack: see swelling and damage.
- Let it cool. A pack straight from a hard flight or run is hot. Let it return to room temperature first.
- Use a LiPo bag. BYU says always use a LiPo bag when charging and never charge unattended. A bag can contain a fire but will not stop one.
- Use proper connectors. BYU warns against makeshift adapters or alligator clips.
- Charge somewhere sensible. West Yorkshire Fire and Rescue says to charge away from escape routes, hallways and combustible materials, ideally where you can keep an eye on the battery. Do not cover chargers or batteries with bedding or cushions.
- Be there. Do not leave batteries charging unattended, including overnight or when you are out. Unplug once full.
- Have a working smoke alarm or heat detector where you charge.
Temperature
West Yorkshire Fire and Rescue advises avoiding storing, using or charging batteries in very hot or very cold conditions. Do not charge in a hot car or direct sun, and do not charge a frozen pack.
Discharging and storage
If you are not flying or driving for several days, do not leave the pack full. Your charger's storage mode takes it to a safe mid-level: see storage voltage.
If something looks wrong
Stop, unplug, and if safe to do so, move away. If it is hot, puffing, hissing or smoking, do not touch it. Fire services say battery fires spread quickly and give off toxic smoke: get out, stay out, call 999.
See ratings explained for how to read your pack's label.
This is general information, not a substitute for the instructions that came with your battery and charger. If your manufacturer's advice differs, follow the manufacturer.
Frequently asked questions
What does balance charging do?
It brings each cell to the same voltage using the balance lead, so no cell is overcharged.
What current should I charge a LiPo at?
BYU's guide sets it from capacity: a 500 mAh pack charges at 0.5 A. Never exceed the maker's recommended rate.
Do I need a LiPo bag?
BYU says always use one when charging. It may contain a fire, but you must still not leave the pack unattended.
Can I charge a swollen LiPo?
No. Never charge a swollen, damaged or punctured pack.