Calculator Inputs
The overall page uses a single-column flow. Inside the calculator, fields use 3 columns on large screens, 2 on medium, and 1 on small devices.
Example Data Table
| Parameter | Example Value | Why It Matters |
|---|---|---|
| Battery chemistry | LiFePO4 | Chemistry changes voltage, self-discharge, and realistic Peukert behavior. |
| Cell nominal voltage | 3.2 V | Nominal cell voltage sets pack voltage after multiplying by series cells. |
| Cell capacity | 100 Ah | Capacity affects stored charge and runtime. |
| Series cells | 4 | Creates a 12.8 V nominal pack. |
| Parallel strings | 1 | Parallel strings increase total amp-hour capacity. |
| Active load / standby load | 120 W / 12 W | Different operating modes produce realistic daily energy demand. |
| Active / standby hours | 6 h / 18 h | Duty cycle converts load into daily consumption. |
| Converter efficiency | 92% | Accounts for electronic conversion losses between battery and device. |
| Usable depth of discharge | 95% | Limits how much stored energy is safely available. |
| Reserve margin | 10% | Preserves emergency energy and reduces over-discharge risk. |
Formula Used
1) Pack Voltage
Pack Voltage = Cell Nominal Voltage × Cells in Series
2) Bank Capacity
Bank Capacity (Ah) = Cell Capacity × Parallel Strings
3) Nominal Stored Energy
Energy (Wh) = Pack Voltage × Bank Capacity
4) Daily Load Energy
Daily Load Energy (Wh/day) = (Active Power × Active Hours) + (Standby Power × Standby Hours)
5) Battery-Side Daily Energy
Battery Energy = Daily Load Energy ÷ Converter Efficiency
6) Peukert-Adjusted Effective Capacity
Effective Capacity = Rated Capacity × (Reference Current ÷ Actual Current)(Peukert Exponent − 1)
7) Usable Capacity After Limits
Usable Capacity = Effective Capacity × Age Factor × Usable Depth of Discharge × (1 − Reserve Margin)
8) Runtime
Runtime (hours) = Usable Capacity ÷ Battery Current
9) Monthly Self-Discharge Loss
Self-Discharge Loss = Nominal Energy × Age Factor × Monthly Self-Discharge Rate
Chemistry matters because different electrochemical systems behave differently under load. Lithium chemistries usually have lower Peukert impact and lower self-discharge than lead-acid or nickel-based systems.
How to Use This Calculator
- Select a chemistry preset or choose custom values.
- Enter cell voltage, capacity, series cells, and parallel strings.
- Enter active and standby loads with daily operating hours.
- Set efficiency, usable depth, reserve margin, and aging inputs.
- Adjust Peukert exponent and self-discharge for realistic chemistry behavior.
- Enter the recharge energy price and analysis period.
- Press the calculate button to show results above the form.
- Use the chart, CSV export, and PDF export for reporting.
FAQs
1) What does this calculator estimate?
It estimates battery runtime, daily energy draw, recharge energy, operating cost, self-discharge loss, and load-sensitive capacity. It also shows battery-side current and discharge-rate effects for more realistic planning.
2) Why does chemistry selection matter?
Different chemistries have different nominal voltages, recommended usable depth of discharge, self-discharge behavior, and load sensitivity. These differences affect runtime, usable energy, efficiency expectations, and long-period storage losses.
3) What is Peukert exponent?
Peukert exponent models how effective capacity changes with discharge current. Higher values mean capacity falls faster at heavier loads. Lead-acid batteries are more affected than most lithium systems.
4) Why include reserve margin?
Reserve margin intentionally leaves part of the battery unused. This supports emergency backup, helps prevent deep discharge, and makes runtime estimates more conservative for real operation.
5) Why separate active and standby loads?
Many devices do not draw one constant power level all day. Separating active and standby periods gives a better daily energy estimate and a more useful cost projection.
6) Does converter efficiency change battery consumption?
Yes. If a converter or inverter is not perfectly efficient, the battery must supply more energy than the device actually uses. That increases current draw and reduces runtime.
7) What does age derating represent?
Age derating represents retained capacity compared with the original rating. For example, 85% means the pack behaves like it only has 85% of its rated capacity available.
8) Are these values exact laboratory results?
No. They are practical engineering estimates. Real performance also depends on temperature, internal resistance, charge state, balancing quality, cut-off limits, and actual discharge curves.