Calculator Inputs
Enter battery pack details and blower demand. Advanced factors help reflect field conditions like temperature, aging, wiring losses, and reserve margin.
Example Data Table
| Scenario | Pack (V, Ah) | Load (W) | Duty | Derate | Health | Reserve | Estimated runtime |
|---|---|---|---|---|---|---|---|
| Standard shift | 14.4 V, 6.0 Ah | 28 W | 100% | 5% | 95% | 10% | ~2 h 37 min |
| Cold weather | 14.4 V, 6.0 Ah | 28 W | 100% | 20% | 95% | 10% | ~2 h 11 min |
| Parallel packs | 14.4 V, 6.0 Ah ×2 | 28 W | 100% | 5% | 95% | 10% | ~5 h 14 min |
Formula Used
1) Pack voltage and capacity
- Vtotal = Vpack × Series
- Ahtotal = Ahpack × Parallel
2) Nominal energy
- Whnominal = Vtotal × Ahtotal
3) Usable energy with field factors
- Whusable = Whnominal × Health × (1 − Derate) × (1 − Reserve) × Efficiency
4) Average load
- If current is provided: Wblower = Vtotal × I
- If power is provided: Wblower = W
- Wavg = (Wblower + Wextra) × Duty
5) Runtime
- Runtime (h) = Whusable ÷ Wavg
How to Use This Calculator
- Enter the battery voltage and capacity from the pack label.
- Set series and parallel counts to match your setup.
- Select whether you know current draw or power draw.
- Add duty cycle, efficiency, derating, health, and reserve.
- Click Calculate Runtime to view results above the form.
- Use Download CSV or Download PDF for records.
Professional Article (Approx. 300 words)
1) Why runtime matters on construction sites
PAPR systems protect workers during high-dust tasks such as concrete cutting, silica remediation, abrasive blasting, and demolition cleanup. Battery runtime determines whether protection can be maintained continuously through the work window. A realistic estimate supports safe work sequencing and reduces the chance of removing respiratory protection due to unexpected power loss.
2) Battery energy inputs and configuration
Battery labels provide voltage and amp-hour capacity, which combine to nominal watt-hours. Series connections increase voltage, while parallel connections increase total capacity. The calculator then applies health, reserve, derating, and efficiency factors to represent aging packs, conservative changeout practice, and conversion losses from the electrical system.
3) Blower load, airflow demand, and duty cycle
Blower power changes with selected speed, filter resistance, and required airflow. If you measure current draw, the calculator converts it to watts using total pack voltage. Duty cycle reduces average consumption when the unit is not running at the stated load continuously, which is common during intermittent cutting, relocation, or mixed-activity shifts.
4) Field factors that shorten runtime
Cold temperatures, clogged filters, and higher-than-expected airflow demand can reduce runtime quickly. Use derating to reflect temperature loss and reserve to keep a margin before low-voltage cutoff. Where conditions vary, set conservative factors and compare predicted runtime to observed runtime for your most common tasks.
5) Using results for shift planning and compliance
Convert the estimated hours and minutes into practical triggers, such as changing batteries at 70–80% of predicted runtime. For long shifts, plan a rotation: one pack in use, one charging, and one ready. Log battery IDs, charge times, and observed runtimes to strengthen respiratory protection programs and improve future forecasts.
FAQs
Q1: What battery values should I enter from the label?
Use the pack’s nominal voltage and amp-hour rating printed on the battery. If the label lists watt-hours, you can back-calculate: Ah = Wh ÷ V, then enter voltage and the calculated Ah.
Q2: How do I choose current draw versus power draw?
If you measured blower current with a meter, select current. If the manual lists watts, select power. Both methods produce the same runtime when inputs represent the same operating condition.
Q3: What does duty cycle mean for a PAPR?
Duty cycle is the percent of time the blower operates at the stated load. Intermittent tasks or variable airflow demands often reduce average power, increasing runtime compared with constant full-load operation.
Q4: Why include reserve energy?
Reserve energy keeps a margin so the pack doesn’t run to the cutoff point. This helps avoid sudden shutdowns during critical work and reflects real-world practice where crews change batteries before they are fully depleted.
Q5: How should I set cold-weather derating?
In cold environments, battery output can drop. A common starting point is 10–25% derating depending on temperature and pack chemistry. Use site observations to refine the factor for your specific batteries.
Q6: Does filter loading affect runtime?
Yes. As filters load with dust, the blower may work harder to maintain airflow, raising power draw and reducing runtime. When you notice faster battery drain, inspect filters and verify airflow performance.
Q7: Can I combine multiple batteries?
Yes. Series increases voltage and parallel increases capacity. Enter the number of packs in series and parallel to match your configuration, then ensure connectors and approved accessories are used per manufacturer guidance.