Batteries: what the regulation says, and what it does not
No European text of the ‘open’ category sets a temperature, a charging rule or a storage method for batteries. That absence is not a void: it refers you to a source which is itself binding.
Key points
- The enforceable limits are those of your own manual. The Delegated Regulation requires the manufacturer to describe the operational limitations, including meteorological conditions (Annex, Part 2, point 18(f), and Part 3, point 19(f)).
- Those instructions are not a commercial recommendation: point UAS.OPEN.060(2)(e) obliges the remote pilot to operate the UAS in accordance with the manufacturer's instructions, including any applicable limitations.
- Before the flight, AMC1 UAS.OPEN.060(1)(d) asks for a charge sufficient for two distinct things: the intended operation, and the need for additional energy in case of an unforeseeable event. No reserve percentage is set.
- The 30 % or 20 % that circulate are habits, not rules. The expected reasoning is a NEED (headwind on the way back, waiting for someone to clear the area, a diversion leg) and not a ratio.
- In flight, class C1, C2 and C3 aircraft must give a clear warning at a low level, with enough margin to land safely. The requirement covers the battery of the aircraft AND that of its control and monitoring unit.
- It really is a warning leaving the pilot time to act, not an automatic manoeuvre deciding in his place. The decision to come home remains his.
- The subcategory A2 syllabus goes further on this point and asks you to understand how a battery works (charging, use, danger, storage) in order to help prevent possible dangerous conditions (AMC1 UAS.OPEN.030(2)(c)). That is a training syllabus, not an article of the regulation.
- Maintenance of the UAS, batteries included, follows the manufacturer’s instructions. The Delegated Regulation imposes those maintenance instructions on classes C1 to C4; Part 1, which governs C0, does not require them.
The trap. Looking here for a European figure (a floor temperature, a reserve percentage, a number of cycles) is looking for what does not exist. The examination does not test a threshold, it tests the chain: the manual sets the limit, and the regulation makes that manual binding.
Source
Implementing Regulation (EU) 2019/947 (CELEX 02019R0947, consolidated on 01/05/2025), Annex Part A, points UAS.OPEN.060(1)(d) and UAS.OPEN.060(2)(e); AMC1 UAS.OPEN.060(1)(d) and AMC1 UAS.OPEN.030(2)(c) (ED Decision 2019/021/R); Delegated Regulation (EU) 2019/945 (CELEX 02019R0945, consolidated on 24/06/2025), Annex, Part 2, points 15 and 18(f), Part 3, points 17 and 19(f), and Part 4, point 13