What is the correct storage charge for a LiPo battery?

Storage charge is typically around 3.7–3.85 V per cell — less than full charge (4.2 V) and more than a depleted state. The exact level is specified in your charger's instruction manual.

What does the C rating mean?

The C rating is the maximum continuous discharge rate as a multiple of capacity. For example, a 2000 mAh battery with a 25C rating can deliver up to 50 A (2 Ah × 25 = 50 A).

Safety & tech

LiPo batteries for the exam

Battery topics are among the most tested areas in A1/A3 and A2 papers.

A2STS editorial12 min readUpdated 29/06/2026

Contents

What is tested in the exam

LiPo batteries are one of the most frequently examined topics in both A1/A3 and A2 papers. TKA question bank items cover battery chemistry, charging procedures, storage and labelling — including cell count (S number), voltage and discharge rating (C rating).

You must be able to calculate battery voltage from the S number (e.g. 3S = 11.1 V nominal, 12.6 V fully charged) and understand what the C rating means during flight operations.

Safety rules in the exam

LiPo cells are thermally unstable when damaged, overcharged or deeply discharged. Exam questions cover: storage charge level, prohibition on unattended charging and the use of LiPo-safe bags.

Questions about damaged or puffy batteries appear frequently — the correct answer is always to remove the battery from service. Identify and avoid the 'continue using with caution' distractor.

Exam tip

Common exam mistakes

Candidates mix up nominal voltage with full-charge voltage, confuse C-rating meaning and get tripped by the difference between LiPo and LiHV chemistry. Another common error is treating any puffed battery as still usable.

Study tip: practise questions where all options seem plausible. The A2STS spaced-repetition engine resurfaces battery questions until you consistently answer them correctly.

How to prepare for the battery topic

The battery topic covers roughly 5–8% of all A1/A3 and A2 questions. Dedicate 2–3 focused study sessions to battery anatomy, charging, storage and disposal.

In A2STS, filter questions by the battery topic category and run 15–20 question sets. After every incorrect answer, read the full explanation before moving on.

Frequently asked questions

What is the correct storage charge for a LiPo battery?: Storage charge is typically around 3.7–3.85 V per cell — less than full charge (4.2 V) and more than a depleted state. The exact level is specified in your charger's instruction manual.
What does the C rating mean?: The C rating is the maximum continuous discharge rate as a multiple of capacity. For example, a 2000 mAh battery with a 25C rating can deliver up to 50 A (2 Ah × 25 = 50 A).

Authority & sources

A2STS Editorial · Reviewed by: EASA UAS syllabus aligned