What does C-rating mean on a LiPo battery?

The C-rating is a multiplier that indicates the maximum safe continuous discharge current. Formula: Max Current (Amps) = Capacity (Ah) × C-Rating. For example, a 1300mAh (1.3Ah) 100C battery claims to deliver up to 130A continuously. However, most budget batteries deliver only 35-50% of their labeled C-rating in real-world conditions.

What C-rating do I need for a 5-inch FPV drone?

For a 6S 1300mAh 5-inch build, look for a labeled C-rating of 100C or higher from a reputable brand. This provides approximately 45-50A continuous real-world current, which handles the 100-140A peak draws during punchouts. Budget batteries below 75C will sag noticeably during aggressive freestyle or racing.

How do I check if my LiPo battery is worn out?

Check internal resistance (IR) with a compatible charger. IR per cell should be under 4mΩ for a good battery, 4-8mΩ for an acceptable aged battery, and above 8mΩ indicates a worn-out pack that will sag badly. Also check for puffing (swollen cells), cells more than 2mΩ apart, and excessive heat after flight.

Understanding FPV LiPo Battery C-Ratings: How to Choose the Right Pack

Q: Are LiPo C-ratings accurate?

No — most C-ratings on consumer FPV batteries are significantly inflated. There is no industry standard for measurement. Independent testing shows that even premium LiPos deliver 35-50% of their advertised C-rating before unacceptable voltage sag occurs. Trusted brands like GNB, Tattu R-Line, and CNHL Black Series perform closest to their ratings.

# Understanding FPV LiPo Battery C-Ratings: How to Choose the Right Pack

Walk into any FPV store and you’ll see batteries labeled 100C, 120C, even 150C. But what do these numbers actually mean? And why does a “100C” battery from one brand perform worse than a “75C” from another? C-ratings are the most misunderstood specification in FPV — here’s the truth about what they mean, how to verify them, and how to choose the right battery for your build.

## What C-Rating Actually Means

The C-rating is a multiplier for the battery’s capacity that tells you its maximum safe continuous discharge current:

**Formula**: Max Current (A) = Capacity (Ah) × C-Rating

| Example Battery | Capacity | C-Rating | Claimed Max Current | Realistic Max Current |
|—————-|———-|———-|——————–|——————–|
| 6S 1300mAh 100C | 1.3Ah | 100C | 130A | ~45-55A |
| 6S 1300mAh 150C | 1.3Ah | 150C | 195A | ~50-60A |
| 4S 1500mAh 75C | 1.5Ah | 75C | 112.5A | ~40-50A |

**The uncomfortable truth**: Most C-ratings on budget and mid-range batteries are marketing fiction. Laboratory testing by the FPV community consistently shows that even premium LiPos deliver 35-50% of their advertised C-rating before voltage sag becomes unacceptable.

## Why C-Ratings Are Inflated

There is no industry standard for measuring C-ratings. A manufacturer can claim 150C by:
– Testing at 25°C (optimal temperature, not real-world)
– Measuring peak burst (0.5 seconds) rather than continuous discharge
– Using a cutoff voltage of 3.0V/cell (your quad would have fallen out of the sky long before)
– Simply printing a higher number because competitors do

The only reliable way to know a battery’s true performance is through independent testing, not the label.

## Real-World C-Rating Translation Table

Based on community testing (including MCSGUY’s battery load testing thread on RCGroups), here’s what labeled C-ratings translate to in reality:

**The brands that actually deliver**: GNB, Tattu R-Line, CNHL Black Series, and Ovonic consistently outperform their rated specs in independent testing. Generic Amazon/AliExpress batteries with 120C labels often fail to deliver 25C in reality.

## How to Calculate Your Actual Current Draw

To know what C-rating you need, first calculate your quad’s real current requirements:

1. **Hover current**: 4-8A for a 5-inch, 2-4A for a 3-inch
2. **Cruising current**: 10-20A for a 5-inch
3. **Full punchout**: 25-35A per motor (100-140A total for 5-inch, 4S/6S)
4. **Typical freestyle flight average**: 20-40A average draw

For a 6S 1300mAh (1.3Ah) battery:
– Minimum C-rating for punchouts: 140A peak / 1.3Ah = 108C (labeled)
– Real C needed: 50A continuous / 1.3Ah = 38C (actual)
– **Recommended label C-rating**: 100C or higher from a reputable brand

## The Parallel Battery Option

If you need more current than a single pack can deliver, parallel two batteries:

| Setup | Capacity | Weight | Max Current (real) |
|——-|———-|——–|——————-|
| 1× 6S 1300mAh 100C | 1300mAh | 210g | ~50A |
| 2× 6S 1300mAh 100C in parallel | 2600mAh | 420g | ~100A |
| 1× 6S 2000mAh 100C | 2000mAh | 310g | ~75A |

Two 1300mAh packs in parallel deliver more current than a single 2000mAh and spread the weight more evenly across the frame, though the total weight is higher.

## C-Rating vs. Internal Resistance (IR)

Internal resistance is a far more honest metric than C-rating. Lower IR = better battery:

**How to measure IR**: Most modern LiPo chargers (ISDT, Hota, ToolkitRC) measure IR during charging. Check all cells — they should be within 1-2mΩ of each other. A cell with significantly higher IR than its neighbors is failing.

## Temperature: The Silent C-Rating Killer

LiPo performance drops dramatically in cold weather:

| Temperature | Available C-Rating | Effect |
|————-|——————-|——–|
| 35°C (95°F) | 100% | Optimal — battery is warm from pre-heating |
| 25°C (77°F) | 90% | Good — room temperature |
| 15°C (59°F) | 75% | Noticeable sag on punchouts |
| 5°C (41°F) | 50% | Significant voltage sag, shorter flights |
| -5°C (23°F) | 30% | Barely flyable — warm packs before flight |

**Winter flying tip**: Keep batteries in an inside pocket close to body heat. Install them only when you’re ready to arm. A battery at 30°C delivers 2-3× the usable current of a battery at 5°C.

## Warning Signs of an Under-Rated Battery

If your battery can’t handle your quad’s current draw, you’ll see:

1. **Voltage sag on punchout**: Battery drops below 3.5V/cell immediately on full throttle. Land and check — if it rebounds above 3.7V, the C-rating is insufficient.
2. **Hot battery after flight**: Battery temperature above 50°C (too hot to hold comfortably). This permanently degrades the battery.
3. **Puffed or swollen cells**: Even slight puffing means the battery has been over-stressed. Retire it — puffed LiPos are a fire risk.
4. **Short flight times with early landing**: The battery sags below your warning voltage early but shows significant capacity remaining when checked.

## The Bottom Line

1. **Buy from trusted brands** — the label C-rating only matters if the brand is honest.
2. **Ignore numbers above 120C** — no LiPo of FPV size can physically deliver more than ~55C continuous.
3. **Monitor IR** — it tells you more about battery health than any label.
4. **Size for 2× your average draw, not your peak** — you spend 95% of your flight at cruising current, not punchout.

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