What Is C Rating on a LiPo Battery? A Beginner’s Guide to Discharge Rates

If you’ve ever stared at a LiPo label that says something like “1300 mAh 75C” and thought… what does that actually mean? You’re not alone. The C rating looks cryptic at first, but once you learn one simple formula and a few safety tips, you’ll be able to choose batteries confidently and avoid problems like voltage sag, overheated packs, and surprise cutoffs.

Why this matters in 2025: modern RC drones and cars can draw huge bursts of current. Pick a battery that’s too “weak” and you’ll feel sluggish punch-outs, brownouts, or a hot, puffed pack. Pick appropriately and everything runs cooler, faster, and lasts longer.

The one-sentence definition

C rating tells you how much current a LiPo can safely deliver relative to its capacity. In practice, maximum continuous current (in amps) ≈ Capacity (in amp-hours) × C rating. This standard explanation appears across reputable battery educators, such as the clear overview by Grepow in their 2024 guide on the topic: “What is the C rating on a LiPo battery” by Grepow.

Continuous vs. burst C (and why “burst” is slippery)

• Continuous C: the current the pack can sustain safely for normal use.
• Burst (or peak) C: short spikes for acceleration or punch-outs. Think seconds, not minutes.

There isn’t a universal standard for how long “burst” lasts—manufacturers vary. Many hobby educators describe burst as only a few seconds; for example, RC Helicopter Fun notes it’s just for very short demands, and not a sustained rating: “LiPo Battery Ratings” by RC Helicopter Fun. Popular FPV educator Oscar Liang also cautions that burst ratings are brief (often within ~10 seconds) and are frequently used as marketing numbers rather than engineering limits: “LiPo Batteries for FPV Drones – Beginner’s Guide” by Oscar Liang.

The only formula you need (with mAh → Ah conversion)

• Step 1: Convert capacity to amp‑hours (Ah). Divide mAh by 1000.
  • Example: 1300 mAh = 1.3 Ah; 5000 mAh = 5.0 Ah.
• Step 2: Multiply by the C rating to estimate maximum continuous current.
  • Max continuous current (A) ≈ Ah × C.

This is the common industry shorthand used by manufacturers and educators (see the calculation examples consolidated by Ufine in 2023–2024: “LiPo battery discharge rate guide” by Ufine).

Take a breath—let’s apply it with real numbers.

Quick examples

• FPV drone pack: 1300 mAh (1.3 Ah) at 75C → 1.3 × 75 = 97.5 A theoretical max continuous.
• RC car pack: 5000 mAh (5.0 Ah) at 50C → 5.0 × 50 = 250 A theoretical max continuous.
• Trainer/plane pack: 2200 mAh (2.2 Ah) at 20C → 2.2 × 20 = 44 A theoretical max continuous.

Important reality check: printed C ratings are often optimistic. Experienced testers and educators caution that headline C numbers can be inflated; Oscar Liang even calls many labels “meaningless” without independent testing and suggests skepticism in his 2024–2025 updates: “LiPo Batteries for FPV Drones – Beginner’s Guide” by Oscar Liang. A practical approach is to apply a realism factor: assume only 50–70% of the labeled continuous C unless it’s a well-tested, trusted brand.

Picking the right C rating (2025 practical guidance)

Here’s a simple process that works for both RC drones and RC cars:

1. Estimate your setup’s current needs. Look at motor and ESC specs or trusted community data. A 5-inch FPV quad can see total peaks ~140–150 A for short bursts, while many 1/10 scale cars peak around 50–100 A depending on gearing and surface. These ranges are consistent with community testing and educator summaries, such as Oscar Liang’s motor/flight current discussions and FPV build guides in 2024–2025: “Motors for FPV drones” by Oscar Liang and the build-selection overview on QuadPartPicker News.
2. Do the math: convert your battery capacity (mAh → Ah), then compute Ah × labeled C.
3. Apply realism: multiply by ~0.5–0.7 to derate the label.
4. Check that the derated current still covers your expected draw with some headroom. If not, step up the C rating (not necessarily the capacity).
5. Sanity-check connectors and wires. For example, XT30 is generally used for lower currents, XT60 for mid-range, and XT90 for higher current setups; poor sizing can overheat connectors. See Amass/XT series data and reputable comparisons for ballpark capabilities and wire gauges: Amass XT series datasheet (2024) and Digi-Key’s XT30/XT60/XT90 comparison thread.

2025-friendly starting points

• 5-inch FPV freestyle/racing (4S/6S): labeled 60–100C, 1000–1500 mAh. Aim for realistic continuous capability in the 30–60C ballpark and watch temps in early flights. Community sources place peak totals around 140–150 A in short bursts; persistent sag or heat means step up C or capacity (or pick a higher-quality pack). See current draw context discussed by educators like Oscar Liang (2024–2025): “LiPo Batteries for FPV Drones – Beginner’s Guide”.
• Cinewhoops/sub‑250 g: labeled 30–60C, 450–850 mAh. Prioritize weight and quality over extreme C claims.
• Long‑range efficiency builds: labeled 20–45C with larger capacities; focus on efficiency and smooth current draw rather than massive bursts.
• 1/10 scale RC cars (2S–3S): labeled 40–80C, 4000–6000 mAh; many setups peak ~50–100 A. Check ESC, gearing, and connectors.
• 1/8 scale high‑power cars: labeled 50–100C. Double‑check connectors (e.g., XT90/EC5), ESC ratings, and pack temps under hard acceleration.

If you’re unsure, stepping up one C band (say, from 45C to 60C) is usually wiser than jumping to a much heavier pack. Weight affects performance and handling.

Voltage sag and heat: what you’ll feel and see

When you punch the throttle, voltage can dip temporarily—this is voltage sag caused by internal resistance. The higher the current, the bigger the drop (this is the same I × R idea you might remember from school). Symptoms include sluggish acceleration, momentary brownouts, or your quad “feeling heavy,” then recovering when you ease off. For a clear explanation of sag in practical terms, see Ride1UP’s battery support article (2023): “Battery voltage sag explained” by Ride1UP.

Heat goes hand in hand with high current and internal resistance—power lost as heat scales with the square of current. Too much heat accelerates aging and can be dangerous. Grepow summarizes overheating risks and mitigation steps in their 2023 guidance: “How to handle battery overheating issues” by Grepow. If your pack is getting hot to hold after a typical run/flight, back off: use gentler throttle, higher C (or higher quality), or larger capacity.

Safety basics you shouldn’t skip

• Use a LiPo‑specific balance charger and never charge unattended. If you notice swelling, unusual odor, smoke, or excessive heat, stop immediately. The FAA’s PackSafe page summarizes lithium battery hazard signs for travelers and consumers (2024): “Lithium batteries – PackSafe” by FAA.
• Store at “storage voltage,” typically about 3.7–3.85 V per cell, in a cool, dry place (a LiPo‑safe bag or fire‑resistant container is smart). Manufacturers commonly recommend this range; see Gens Ace’s LiPo guide (2024) for storage practices: “LiPo battery guide” by Gens Ace. Many modern “smart” systems even auto‑discharge to storage levels after inactivity—Spektrum’s Smart ecosystem documents this behavior around ~3.8–3.9 V/cell (2023–2024): Spektrum G2 charger manual.
• Temperature guardrails: as a beginner rule of thumb, keep case temps under about 140°F (60°C) during use. Typical manufacturer guidance places operating ranges roughly from -4°F to 140°F; charging is safer between 32°F and 113°F. See consolidated ranges from Motoma’s LiPo temperature overview (2024): “LiPo temperature range – safe limits” by Motoma.

Common myths and mistakes

• “Higher C = longer runtime.” No—runtime mainly depends on capacity (mAh/Ah) and how you drive/fly. C is current capability.
• “Burst C is fine for sustained use.” No—burst is for seconds only. Continuous C is what matters for normal operation (see RC Helicopter Fun and Oscar Liang articles cited above).
• “The printed C is absolute truth.” Be skeptical; treat labels as optimistic and use realistic derating unless you’ve seen trustworthy test data (as warned by Oscar Liang 2024–2025).
• “Any connector will do.” Undersized connectors and wires can overheat. Match XT30/XT60/XT90 (or EC3/EC5/IC5) to your current.
• “If it’s only warm, it’s fine forever.” Persistent heat and swelling are early warning signs; retire questionable packs. Oscar Liang’s safety notes on aging and swelling are helpful (2024): “When to retire a LiPo battery” by Oscar Liang.

Mini glossary (plain language)

• Capacity (mAh/Ah): How much energy the battery can store. 1000 mAh = 1 Ah.
• C rating: How many “times its capacity per hour” the pack can safely deliver.
• Continuous vs. burst: Continuous is safe for regular use; burst is just short spikes.
• Voltage sag: Temporary voltage drop under heavy load; feels like sluggishness.
• Internal resistance (IR): The battery’s internal “friction” that causes sag and heat.

Quick checklist before your first run/flight

• Do the math: Ah × C, then apply 0.5–0.7 realism. Is it enough for your setup?
• Verify connectors/wire gauge (e.g., XT60 for mid‑range, XT90 for higher currents).
• First sessions: monitor pack and ESC temps; stop if the pack gets hot to hold.
• Use a balance charger; don’t leave charging unattended; charge on a non‑flammable surface.
• After use, let the pack rest; if storing for more than a day or two, set storage voltage ~3.7–3.85 V/cell.

You’ve got this

If C ratings have felt like alphabet soup, you’re already through the hardest part. With one formula, a bit of realistic derating, and a few safety habits, you can pick batteries that make your drone or car feel great and stay reliable. If in doubt, choose quality, watch temperatures, and keep learning from your own data logs and the community.