Lithium polymer (LiPo) packs power most drones (RPAS). They are capable but can cause fire or loss of flight if charged, transported, used or stored incorrectly.
This article summarises the official AACR material:
Rules and safety measures for charging, transport, operation and storage of lithium polymer batteries
Source: uas.caa.ro — official AACR document (Romanian Civil Aviation Authority).
LiPo characteristics
- Maximum charge voltage: 4.2 V / cell
- Minimum discharge voltage: 3 V / cell
- Cell voltage difference: max 5 mV
- Discharge rate (“C”): max power relative to capacity
Example: 12 Ah × 10C = 120 A
Labels usually show: cell count (S = series, P = parallel), capacity, voltage, main connector, balance connector and discharge rate.
Key information
- Never charge, discharge or keep a pack that is swollen, punctured or impact-damaged.
- Use a dedicated LiPo charger only, with the correct battery type set in software.
- Charge away from flammable materials, in a safety bag or metal box; never leave unattended.
- Transport in a metal box or fireproof bag; avoid sun / over 60 °C; in cold weather use thermal protection (below -10 °C the pack can fail suddenly).
- In flight: monitor voltage; fit a LiPo buzzer set to 3.6 V/cell; do not go below 3 V/cell.
- Storage: STORAGE mode at 3.6–3.8 V/cell if you will not fly for 2–3 days; room temperature; no flammable materials; keep a powder extinguisher (P) nearby.
- Faulty pack: dispose of it immediately, separately from healthy packs.
Charging
- Never a swollen, punctured or damaged pack.
- Dedicated LiPo charger; correct type selected.
- Area free of flammable materials.
- Do not exceed 4.2 V/cell.
- During charge: safety bag or metal box + supervision.
- Do not charge in a car or near the engine — use a safe platform beside the vehicle.
- Do not charge packs warmer than ambient temperature; let them cool first.
Transport
- Metal box or fireproof safety bag.
- In a flight case: protect against puncture, impact and short circuit.
- Do not leave in sun or enclosed spaces where temperature may exceed 60 °C.
- In cold weather: thermal protection; below -10 °C chemistry slows and the pack may fail suddenly.
- For air travel: check the airline’s rules in advance.
Operation (in flight)
- If possible, continuously monitor voltage and instantaneous current — abnormal draw may indicate a technical problem.
- Fit a LiPo buzzer on every pack on the RPAS, set to 3.6 V/cell.
- Before flight: check voltage and cell balance.
- Do not operate below -10 °C.
- Do not discharge below 3 V/cell — at 2.9 V/cell the pack can be permanently destroyed.
- Do not exceed the manufacturer’s discharge rate.
Storage
- Do not leave at full charge for more than 2–3 days. If you will not fly, switch to STORAGE (3.6–3.8 V/cell).
- Room temperature. Not in a fridge (condensation → short-circuit risk) and not in the sun.
- Do not fill the container completely; arrange charge leads and balance connectors to avoid shorts.
- Area free of flammable materials.
- Never store a faulty pack with the others — dispose of it immediately.
- In the storage/charging area: powder extinguisher (symbol P).
Disposal procedure
Per AACR:
- Fully discharge the pack with a load on the terminals — not by shorting the terminals, and avoid discharging through the RPAS.
- Confirm voltage is below 1–2 V.
- Submerge the pack in salt water for 2 days, including charge and balance terminals. Wear gloves and safety glasses.
- Before discarding, confirm voltage has reached 0 V. The chemistry converts to non-toxic components and the pack may then be discarded as described in the official document.
What it means for you
Before every flight: inspect the pack, check voltage and balance, fit the buzzer, confirm temperature and energy reserve.
After flight: let it cool; if you will not fly within 2–3 days, set STORAGE.
Any swelling, impact or fault: remove from service and dispose of it — do not “try one more flight”.
FAQ
Where is the official document?
On the AACR UAS portal: uas.caa.ro/storage?id=133841. This article is a summary; AACR remains the reference.
What voltage for STORAGE?
3.6–3.8 V per cell if you will not fly soon (max 2–3 days at full charge).
Can I charge LiPo in the car?
No. Do not charge in the vehicle or near the engine. Use a safe platform outside, with a safety bag / metal box and supervision.
What about a swollen pack?
Do not charge it, store it with others, or fly it. Dispose of it using the AACR procedure (controlled discharge → salt water → 0 V).
Does Drone Log replace AACR?
No. It helps you plan and document flights. For LiPo, follow the official AACR material and the manufacturer manual.
To move from theory to practice, check if you can fly or use the airspace checker. If the zone requires it, generate the approval request.