What does the C-rating mean?

The C-rating tells you the maximum safe continuous discharge rate. A 30C 5000mAh battery can deliver 30 x 5 = 150 amps continuously. Higher C-ratings mean the battery can deliver more current without overheating or puffing. Always choose a battery with a C-rating that exceeds your motor maximum draw.

How many cells (S) do I need?

The cell count determines voltage. 2S (7.4V) suits smaller models. 3S (11.1V) is the most common for general RC use. 4S (14.8V) and 6S (22.2V) are used for high-performance models. Match the cell count to your ESC and motor specifications.

Why do I only get 80% of the rated capacity?

Discharging a LiPo below 3.3V per cell damages it permanently. The usable capacity is about 80% of the rated capacity. Never run a LiPo flat — use a low-voltage alarm. For maximum lifespan, some pilots only use 70% of capacity.

How do I calculate run time?

Run time (mins) = (Usable capacity in Ah / Average current draw in A) x 60. For example, a 5000mAh battery at 80% usable (4000mAh) with 20A average draw gives 0.2 hours = 12 minutes. Actual run time varies with throttle usage.

ModelCalcs

Battery Calculator — RC Power Planning

Calculate battery capacity, C-rating, discharge rate and run time for your RC model.

Capacity (mAh)

Value for capacity (mah)

Cell Count (S)

Select an option for cell count (s)

Battery Type

Select the type

C-Rating

Value for c-rating

Average Current Draw (A)

Typical average during use

How We Calculate This

Calculates battery voltage, maximum current delivery and estimated run time from battery specifications.

Formula

Voltage = Cell count x Nominal cell voltage
Max current = (Capacity mAh / 1000) x C-rating
Watt-hours = (Capacity / 1000) x Voltage
Run time = (Capacity x 0.8) / (Avg current x 1000) x 60 mins

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify quantities before purchasing materials.