Energy & Environment · Storage and grids / Principles and inquiry
Battery capacity and discharge rate experiment guide
Vary discharge rate to compare delivered energy under the voltage curve and usable capacity.
How does it work?
At high discharge rates, usable capacity falls and internal voltage drop grows. Equal Ah does not guarantee equal energy.
I = Cnom r · Ceff = Cnom/[1 + 0.08 max(0,r−1)] · E(Wh) = ∫VI dt(h)
Try this investigation
- Vary discharge rate to compare delivered energy under the voltage curve and usable capacity.
- Run and record each of the three reference settings.
- Change one variable in each comparison and compare its energy results with the baseline.
Interpreting your results
How is energy found when voltage changes over time?
Integrate voltage times current over time · At high discharge rates, usable capacity falls and internal voltage drop grows. Equal Ah does not guarantee equal energy.
Assumptions and limitations
Open-circuit voltage is 3.2+state-of-charge V with 0.06 Ω internal resistance and empirical rate-dependent capacity. It does not predict a specific cell; temperature, aging and protection are omitted. Do not dismantle, short, heat or discharge real batteries under these conditions.