Battery capacity

Charge used in a match, share of the battery, and runtime at an average current.

Inputs

Rated capacity

Average current

Match length

2:40 in 2026 REBUILT (20 s auto + 2:20 teleop).

Usable share of capacity

Lead-acid batteries give far less than rated capacity at high current.

Nominal voltage

Result

Charge used per match

2.222

Share of usable charge: 20.58%
Runtime at this current: 12.96
Rated energy: 216

How it’s calculated

Formula

Q_\text{match} = I \, t

t_\text{run} = \frac{u \, C}{I}, \qquad E = V \, C

With your numbers (converted to SI units)

Q_\text{match} = 50\,\text{A} \times 160\,\text{s} = 8000\,\text{C} = 2.222\,\text{Ah}

t_\text{run} = \frac{0.6 \times 64800\,\text{C}\ (18\,\text{Ah})}{50\,\text{A}} = 777.6\,\text{s}

What it means

Rated capacity assumes a slow 20-hour discharge. At FRC currents a lead-acid battery delivers much less (the Peukert effect), so plan with the usable share. A match that uses a large share of the usable charge tends to sag noticeably near the end.

Assumptions

Constant average current.
The usable share is an estimate; test your batteries with a load tester.

Learn the concepts behind this on resources.simbotics.org · All formulas