The Truth About LiPo C-Ratings
On paper, the C-rating tells you how much continuous current a pack can deliver:
Max current (A) = capacity (Ah) × C
A 1300 mAh 100C pack therefore "supports" 1.3 × 100 = 130 A. A 5" freestyle quad pulls 80–120 A at full throttle, so that pack looks comfortable.
Why the label lies
C-ratings are marketing numbers with no industry-standard test behind them. Two "100C" packs from different brands can behave completely differently. The number printed on the wrapper is best treated as a relative tier within one brand, not a physical guarantee.
What actually limits a pack is internal resistance (IR): the lower the IR, the less voltage the pack loses under load and the less heat it makes. Quality packs with honest ~100C labels typically sit around 1–2 mΩ per cell when new; tired or cheap packs drift far higher.
How to judge a battery in the real world
- Sag test. Punch out; if a fully charged 6S pack dips below ~3.3 V per cell on the OSD, it is under-spec'd (or worn out) for your setup.
- Temperature test. Land after a normal flight and feel the pack. Warm is fine; too hot to hold comfortably means it is being pushed past its real rating.
- IR trend. Most smart chargers report per-cell IR. Log it when new and watch it climb as the pack ages.
Practical buying advice
- More capacity at the same C = more real current headroom. A 6S 1300 100C and a 6S 1100 120C are theoretically similar (130 A vs 132 A); the bigger pack usually sags less.
- Racing needs burst delivery (sag under punch decides races); long range barely needs C at all — that is why Li-ion packs with tiny C-ratings dominate cruising builds.
- Check whether the drone maker publishes a recommended C floor — the quads in our database list the manufacturer's battery specs.
Run your own numbers in the battery current draw checker.