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LiPo Battery C Rating (2025): Choose the Right Specs for Your Drone, Plane, Car, or Robot

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Mari Chen

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LiPo Battery C Rating explained with simple formula and RC models

If C ratings on LiPo packs make your head spin, you’re not alone. The good news: once you learn one simple idea and a tiny bit of math, choosing the right battery becomes straightforward. This guide walks you through it step by step—with real examples for drones, planes, RC cars, and small robots—so you can buy with confidence and avoid puffing, cutoffs, and hot packs.

What you’ll learn in a minute:

  • C rating is just a multiplier tied to capacity (Ah) that tells you how many amps a pack can deliver continuously.
  • Continuous C matters more than burst. Burst is a short spike, not something you can hold.
  • A quick 4-step method will get you the right C rating with safe headroom.

According to the updated 2025 community-focused overview in the Oscar Liang LiPo battery guide, C is best treated as practical guidance—brands vary, and labels can be optimistic—so you’ll add a bit of margin and sanity-check with real-world signs like temperature and voltage sag.

The 60‑second crash course: what “C” means (with one tiny formula)

  • Capacity is in amp-hours (Ah). A 1500mAh pack is 1.5Ah.
  • Continuous current capability ≈ Capacity (Ah) × C rating.
  • Example: 1.5Ah × 25C ≈ 37.5 amps continuous.

That’s it. If your vehicle needs around 35–40A continuously, a 1.5Ah 25C pack is in the ballpark. This approach—capacity times C—matches the beginner-friendly explanation in the 2025 Oscar Liang guide on LiPos.

A quick word on “burst C”: It’s a short peak (often only a few seconds) and varies by brand. Treat it as a temporary reserve, not a number you can rely on for long climbs or long pulls. The same principle—that continuous spec matters most—is echoed throughout Oscar Liang’s 2025 resource on LiPos and ESCs: see the ESC overview (2025).

The 4‑step method to pick your C rating (with headroom)

  • Step 1: Estimate your max current draw.

    • Use your ESC/motor specs, community averages, or telemetry/logs if you have them. For example, a typical 5-inch FPV quad can peak around 80–100A total, while cruising is lower. These ranges align with practical figures summarized in the Oscar Liang motor and ESC guides (2023–2025).
  • Step 2: Compute the required continuous C.

    • Required C = Max current (A) ÷ Capacity (Ah).
    • Example: If you expect 60A max and you’re using a 1300mAh (1.3Ah) pack, 60 ÷ 1.3 ≈ 46C.
  • Step 3: Add 20–30% safety margin.

    • This accounts for label optimism, temperature changes, and aging. For 46C, target around 55–60C continuous on the label.
  • Step 4: Sanity-check with real-world signs.

    • If packs run hot (approaching ~60–65°C), sag badly under throttle, or trigger early cutoffs, you may need a higher C (or larger capacity) or better airflow. Practical limits and warning signs are consistent with the 2025 guidance in the Oscar Liang LiPo guide.

Worked examples for common setups

  • FPV 5-inch quad (4S 1300mAh):
    • Max draw ~60A (conservative planning). Required C ≈ 60 ÷ 1.3 = 46C. Choose a reputable 60–80C pack.
  • RC plane trainer (3S 2200mAh):
    • Peak ~25A on climb; cruise ~6–12A. Required C ≈ 25 ÷ 2.2 ≈ 11.4C. A lighter, good 20–30C pack is plenty.
  • 1/10 RC basher (2S 5000mAh):
    • Hard launches can hit 120A. Required C = 120 ÷ 5 = 24C. Choose a solid 35–50C pack for heat margin.
  • Small 3S robot (1500mAh) with DC gearmotors:
    • Occasional stall peaks ~30A total. Required C = 30 ÷ 1.5 = 20C. Pick 30–45C and add a fuse to protect electronics.

These ranges and trade‑offs are consistent with community-tested norms captured in the Oscar Liang 2025 LiPo overview, which also reminds us that labels vary by brand.

Continuous vs. burst C: what’s real, what’s marketing

  • Continuous C: What the pack can handle for sustained periods without overheating or excessive voltage sag.
  • Burst C: A short spike—think a few seconds—that helps with punchy maneuvers or hard launches. Don’t size your whole system to burst numbers.

Treat burst as a bonus. Most ESCs even separate “continuous” vs. “burst” current for only a few seconds, mirroring this reality in electronics specs; see the ESC overview by Oscar Liang (2025).

Why not just buy the highest C rating?

  • Higher C packs are often heavier and more expensive. In drones and planes, extra weight hurts flight time and handling.
  • If you never draw near that current, you won’t notice the benefit—but you will carry the weight.
  • Real-world performance depends on cell quality and internal resistance (IR), not just the printed C. Two “75C” packs can behave very differently. This caution is emphasized in the 2025 Oscar Liang LiPo guide.

Voltage sag, internal resistance, and temperature (what you’ll feel)

  • Higher internal resistance causes more voltage sag under throttle. It feels like weak acceleration or “no punch,” and you may hit low-voltage cutoff early.
  • Temperature affects IR: cold weather increases IR (more sag), warm reduces IR—but running too hot accelerates wear.
  • Keep an eye on pack temperature and behavior. These practical effects and mitigation tips are explained in the Oscar Liang LiPo guide (updated 2025).

Charging and storage basics you should adopt from day one

  • Charge at 1C by default and balance-charge every time. Faster charging (like 2C) is only OK if the manufacturer clearly says so, and it can shorten lifespan. Horizon Hobby’s safety content reiterates this 1C baseline and balance charging in their 2024 LiPo charger guidance.
  • Store at about 3.80–3.85V per cell (roughly half-full). This storage range helps minimize degradation during downtime, as summarized in Horizon Hobby’s LiPo safety sheet (PDF, 2024) and the 2025 Oscar Liang guide.
  • Respect temperature limits: general Li‑ion guidance is to charge around 0–45°C (32–113°F) and operate roughly −20 to 60°C (−4 to 140°F). Charging below freezing risks lithium plating; running too hot hastens aging. See the engineering overview of Li‑ion charging conditions in TI’s Li‑ion charging terminology note and the temperature cautions discussed in Battery University’s charging lithium at low/high temps explainer.

Low-voltage cutoff (LVC) and when to land/stop

  • Many ESCs offer per‑cell LVC options around ~3.0–3.4V. Hobbywing documents multiple per‑cell thresholds and modes in their recent manuals (see the 2023 manual PDF example and the 2024 manual PDF). Spektrum’s Smart ESCs have similar modes; see the 2024 Firma Smart ESC manual.
  • Practical habit: For longevity, land around 3.5–3.6V per cell under load (your resting voltage will bounce back higher). This rule of thumb aligns with community practice summarized in the Oscar Liang LiPo guide (2025).

Connectors and wire gauge: don’t bottleneck your current

Your connector and wiring need to handle the same current you sized your battery for—otherwise you’ll generate heat and sag.

  • Common XT connectors used in RC: XT30 ≈ 30A, XT60 ≈ 60A, XT90 ≈ 90A in practical continuous use, with short bursts higher. Ensure your wire gauge matches the current (e.g., 16–14 AWG for 60–100A short runs). These are widely accepted community norms collected in the Oscar Liang connectors and wires guide. Actual ratings vary by brand, wire length, and cooling, so stay conservative.

Application-specific tips (2025)

  • Drones (FPV/racing/freestyle)

    • Prioritize enough C for punch, but remember weight. If your quad sags on hard punchouts or lands early, try a higher-C or slightly larger capacity pack from a reputable brand. Modern setups often log current/voltage—use that data.
    • Smart ecosystems are growing. Telemetry and “smart” packs/ESCs can help manage cutoffs and monitor health; see Spektrum’s Smart LiPos and ESC telemetry described in the Spektrum Smart ecosystem manual (2024) and an example Smart LiPo product page.
  • RC planes (trainers, gliders)

    • You can usually choose a lighter, lower‑C pack because average current is low. Size to your climb current plus margin, not to long, hot climbs you’ll rarely do.
    • Keep airflow over the battery during long climbs in warm weather to avoid heat buildup.
  • RC cars (bashers, crawlers)

    • Hard launches and grass/sand cause big current spikes. Size for bursts with comfortable headroom and check temps after a few hard runs. Crawlers draw less but can see stall spikes—still give yourself margin.
    • Ensure the pack fits securely with good airflow; heavy packs can raise center of gravity and roll risk.
  • Robotics (STEM/mobile bots)

    • Consider stall currents of your motors. Brownouts that reset your microcontroller are a clue you need more headroom—or a separate logic supply. Add fusing to protect wiring and electronics.
    • If your bot runs in cold environments, expect more sag; either use a higher‑C pack or keep batteries warm before use.

Quick troubleshooting: if things don’t feel right

  • Early cutoff or weak punch? Check for voltage sag: try a higher‑C or larger‑capacity pack; verify connectors and wire gauge; review LVC settings (see Hobbywing 2024 manual).
  • Pack getting hot (near 60–65°C)? Ease off current, improve cooling, choose higher‑C or bigger capacity, or shorten hard pulls. Persistent high temps shorten life, as general Li‑ion guidance and RC practice warn (see TI’s charging note for thermal cautions context).
  • Cells drifting out of balance? Balance charge at 1C and recheck. If drift continues or IR is rising, retire the pack.

Safety and longevity checklist

  • Always balance charge at 1C unless the maker clearly allows higher.
  • Never leave charging unattended; use a LiPo bag or fire‑safe setup.
  • Stop using packs that puff, get excessively hot, or have damaged wires/insulation.
  • Land/stop around 3.5–3.6V per cell under load; don’t rely on deep cutoffs to save a flight or run.
  • Store around 3.80–3.85V per cell in a cool, dry place.
  • Match connectors and wire gauge to your current needs; avoid undersized adapters.

Mini FAQ

  • Do I need the highest C rating available? Usually no. Pick enough continuous C (with 20–30% headroom) for your real current needs; extra C adds weight and cost without benefits if you don’t use it.
  • My pack says 100C but still sags—why? Labels vary. Cell quality and internal resistance matter. Two “100C” packs can perform very differently. Trust reputable brands and your own temp/sag observations, as highlighted in the 2025 Oscar Liang guide.
  • Can I charge at 2C to save time? Only if the manufacturer explicitly allows it. Otherwise stick to 1C to preserve lifespan; see Horizon Hobby’s 2024 charger guidance.
  • What temperature is “too hot”? If it’s uncomfortably hot to the touch, you’re close. Around 60–65°C (140–150°F) is a practical stop‑use region cited widely in RC practice and consistent with Li‑ion aging behavior discussed in engineering and safety resources like TI’s charging overview.

You’ve got this

If you remember just one thing: Amps = Ah × C. Estimate your current, compute the required C, add 20–30% headroom, and verify with temperature and sag. Do that, and you’ll pick the right pack for your drone, plane, car, or robot—and your batteries will last longer and perform better.