Unbound Solar Battery Calculator

Battery Capacity Formula:

\[ \text{Battery Capacity (Ah)} = \frac{\text{Monthly Bill (\$)} / 30 \text{ (days)} \times 1000}{\text{Voltage (V)} \times \text{DoD} \times \text{Efficiency}} \]

Monthly Bill:

Voltage:

Depth of Discharge (DoD):

decimal (0-1)

Efficiency:

decimal (0-1)

Battery Capacity:

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1. What is the Unbound Solar Battery Calculator?

The Unbound Solar Battery Calculator estimates the required battery capacity (in amp-hours) for a solar power system based on your monthly electricity bill and system parameters. This method helps size batteries appropriately for off-grid or backup power systems.

2. How Does the Calculator Work?

The calculator uses the Unbound Solar formula:

\[ \text{Battery Capacity (Ah)} = \frac{\text{Monthly Bill (\$)} / 30 \text{ (days)} \times 1000}{\text{Voltage (V)} \times \text{DoD} \times \text{Efficiency}} \]

Where:

$ \text{Monthly Bill} $ — Your average monthly electricity bill in dollars
$ \text{Voltage} $ — System voltage (typically 12V, 24V, or 48V)
$ \text{DoD} $ — Depth of Discharge (fraction of battery capacity that can be safely used)
$ \text{Efficiency} $ — System efficiency (typically 0.85-0.95 for lead-acid, 0.95-0.98 for lithium)

Explanation: The formula converts your monthly energy cost to daily watt-hour requirements, then calculates the battery capacity needed to store that energy.

3. Importance of Battery Sizing

Details: Proper battery sizing is crucial for system reliability. Undersized batteries may not meet your energy needs, while oversized batteries increase costs unnecessarily.

4. Using the Calculator

Tips:

For DoD: Use 0.5 for lead-acid batteries, 0.8-0.9 for lithium batteries
For Efficiency: Use 0.85 for lead-acid, 0.95 for lithium systems
Voltage should match your system voltage (12V, 24V, or 48V most common)

5. Frequently Asked Questions (FAQ)

Q1: Why use monthly bill instead of kWh usage?
A: Many people know their electricity bill but not their exact kWh usage. The calculator estimates energy needs from cost.

Q2: What's a typical DoD value?
A: 50% for lead-acid (0.5), 80-90% for lithium (0.8-0.9) to maximize battery life.

Q3: How accurate is this calculation?
A: It provides a rough estimate. Actual needs may vary based on usage patterns and weather conditions.

Q4: Should I round up the battery size?
A: Yes, it's recommended to round up to the nearest standard battery size and consider adding 10-20% margin.

Q5: Can I use this for grid-tied systems?
A: This is primarily for off-grid systems. Grid-tied battery sizing depends on backup requirements during outages.