Rechargeable Battery Calculator

Battery Backup Time Formula:

\[ \text{Backup Time (h)} = \frac{\text{Battery Capacity (Ah)} \times \text{Battery Voltage (V)} \times \text{Depth of Discharge} \times \text{Efficiency}}{\text{Load Power (W)}} \]

Battery Capacity:

Battery Voltage:

Depth of Discharge:

(0-1)

Efficiency:

(0-1)

Load Power:

Backup Time:

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1. What is the Battery Backup Time Calculation?

The battery backup time calculation estimates how long a rechargeable battery can power a device before needing recharging. It considers the battery's capacity, voltage, acceptable discharge level, system efficiency, and the power consumption of the connected load.

2. How Does the Calculator Work?

The calculator uses the following equation:

\[ \text{Backup Time (h)} = \frac{\text{Battery Capacity (Ah)} \times \text{Battery Voltage (V)} \times \text{Depth of Discharge} \times \text{Efficiency}}{\text{Load Power (W)}} \]

Where:

Battery Capacity — The total charge stored in the battery (Amp-hours)
Battery Voltage — The nominal voltage of the battery (Volts)
Depth of Discharge — Fraction of battery capacity that can be used (0-1)
Efficiency — System efficiency including inverter and other losses (0-1)
Load Power — The power consumption of the connected device (Watts)

Explanation: The equation converts battery capacity to energy (Wh), applies discharge and efficiency factors, then divides by load power to get runtime.

3. Importance of Battery Runtime Calculation

Details: Accurate runtime estimation is crucial for designing reliable power systems, sizing batteries appropriately, and ensuring uninterrupted operation of critical devices.

4. Using the Calculator

Tips: Enter all values in the specified units. Typical values: Depth of Discharge (0.5-0.8 for lead-acid, 0.8-0.9 for lithium), Efficiency (0.85-0.95 for good systems).

5. Frequently Asked Questions (FAQ)

Q1: Why is Depth of Discharge important?
A: It affects both runtime and battery lifespan. Deeper discharges reduce battery cycle life, especially for lead-acid batteries.

Q2: What are typical efficiency values?
A: 90-95% for lithium systems, 80-85% for lead-acid with inverter, up to 98% for DC-DC systems.

Q3: How does temperature affect runtime?
A: Cold temperatures reduce battery capacity (especially lead-acid) while high temperatures can reduce lifespan.

Q4: Should I derate manufacturer's capacity ratings?
A: Yes, especially for lead-acid batteries. Real-world capacity is often 10-20% less than rated capacity.

Q5: How does battery age affect calculations?
A: As batteries age, their capacity decreases. For older batteries, use 70-80% of original capacity in calculations.