Do you stare at battery labels confused by the "C" number? Choosing the wrong discharge rate can cause mid-air power failure, bloated packs, or wasted budget. Let’s decode this critical specification.
"90C" represents the battery's maximum safe continuous discharge rate relative to its capacity. It means the battery can deliver current equal to 90 times its capacity without overheating. For example, a 5000mAh (5Ah) battery at 90C can output 450 Amps of continuous power.
Understanding the definition is just the start. In the factory, I see many procurement managers buy high C-ratings without understanding the physics, or worse, buy low C-ratings for heavy-lift drones. This leads to either wasted money on heavy batteries you don't need, or mismatched hardware that crashes. Let's look at how to calculate your actual power needs and apply this to your fleet.
How do you calculate the actual current output?
You cannot know the power output just by looking at the "C" number alone; it is a multiplier, not a fixed value.
To find the maximum current (Amps), multiply the capacity in Amp-hours (Ah) by the C-rating. A 90C battery with high capacity delivers massive power, while a small battery with 90C might still be insufficient for heavy drones.
As a manufacturer, I always tell my clients: The "C" stands for Capacity. To get the real data, you have to do a little math. This is vital when you are matching a battery to the motors of your heavy-lift UAVs.
The formula is simple: Continuous Current (A) = Capacity (Ah) × C-Rating
Let’s take a standard battery we might ship to a client like you for a heavy-lift drone:
- Capacity: 5000mAh (which is 5.0 Ah)
- Rating: 90C
- Calculation: 5.0 × 90 = 450 Amps.
This means you can pull 450 Amps from this pack continuously without damaging it.
Now, compare that to a smaller battery for a survey drone:
- Capacity: 1000mAh (1.0 Ah)
- Rating: 90C
- Calculation: 1.0 × 90 = 90 Amps.
See the difference? Both are "90C" batteries. But one provides enough power to lift a cinema camera, while the other might struggle to power a large racing drone. When you look at the spec sheet, always convert the mAh to Ah (divide by 1000) and multiply by the C number. This gives you the "Amp limit." If your drone motors pull 100 Amps at full throttle, and your battery calculation only gives you 90 Amps, that battery will overheat, puff up, and fail.
| Battery Capacity | C-Rating | Max Continuous Amps | Application |
|---|---|---|---|
| 1500mAh (1.5Ah) | 90C | 135 A | FPV Racing |
| 5000mAh (5.0Ah) | 90C | 450 A | Cinema/Heavy Lift |
| 22000mAh (22Ah) | 25C | 550 A | Agricultural/Industrial |
Why does your drone need such a high discharge rate?
High numbers look good on paper, but do they actually help your specific mission profile in the real world?
High C-ratings prevent "voltage sag" during rapid climbs or heavy lifting. If the battery cannot supply the requested current fast enough, voltage drops, causing the drone to feel sluggish or trigger a low-battery landing prematurely.
In my experience working with clients in the Middle East and Russia, I often explain that "90C" is about "stiffness" of the power delivery. Imagine sipping a milkshake. If you use a tiny straw (Low C-rating), it is hard to get the liquid out quickly. You have to suck really hard, and the flow is slow. If you use a giant pipe (90C), the liquid flows instantly with zero resistance.
For your drones, this "resistance" is called Internal Resistance (IR). High C-rating batteries generally have lower Internal Resistance.
Why does this matter for Omar?
- Voltage Sag: When you push the throttle to 100% to lift a heavy payload, the motors demand instant current. A low C-rating battery cannot release electrons fast enough. The voltage drops instantly. Your ground station might beep "Low Voltage Warning" even if the battery is 80% full. A 90C battery holds the voltage steady (stiff) even under load.
- Heat: This is the big killer. Resistance creates heat. If you use a low C-rating battery near its limit, it gets incredibly hot. In 40°C desert heat, an overheating battery is a fire risk. A 90C battery running at half capacity stays cool.
- Response: For FPV or agile drones, you need instant torque. 90C gives you that "punch." For agricultural drones that fly slow and steady, you might not need 90C; a 25C solid-state battery might offer better flight time per gram. It is all about matching the tool to the job.
Can you trust every "90C" label you see?
In the battery market, not all printed numbers reflect reality, and some labels are purely for marketing.
Many manufacturers inflate C-ratings to sell products. A "90C" sticker does not guarantee performance if the internal resistance is high. Always verify with datasheets and choose reputable suppliers who test their cells under real industrial loads.
This is an uncomfortable truth in our industry: Ink is cheap. It costs nothing to print "150C" on a label. But building a cell that can actually handle that heat requires expensive materials and precise folding technology.
I often test competitor batteries in our KKLIPO lab. I see packs labeled "90C" that overheat and puff up at just 50C load. This is dangerous. If you build your system assuming you have 90C of headroom, but you only have 50C, you are flying on the edge of failure.
How can a procurement manager spot a fake?
- Weight: High discharge capability usually requires thicker copper foils and cathode tabs inside the cell. If a battery claims 90C but is suspiciously lighter than a known 60C battery of the same capacity, be skeptical. Physics has weight.
- Price: High C-rate capability is expensive to manufacture. If the price is too good to be true, it is likely a standard 25C or 40C cell wrapped in a 90C label.
- Temperature: Test a sample. Fly it hard. Land and touch the battery. It should be warm, not hot. If it is too hot to hold comfortably, the C-rating is likely exaggerated or you are pushing it too hard.
- Burst vs. Continuous: Pay attention to the fine print. Sometimes "90C" refers to a "Burst" (3 seconds max), while the continuous rate is only 45C. We always specify both clearly (e.g., 90C Continuous / 180C Burst) so engineers can plan safely.
At KKLIPO, we focus on industrial reliability. Sometimes a true, stable 25C solid-state battery is better for a mapping drone than a fake 90C LiPo. But when you need raw power, you need a verified high C-rating.
Conclusion
A 90C rating indicates a high-performance battery capable of massive power delivery. To ensure safety and efficiency, always calculate the specific amperage your drone requires before purchasing.