1. What is the Intruder Alarm Battery Size Calculator?

This calculator determines the appropriate battery size (in amp-hours) needed to power an intruder alarm system through an inverter for a specified duration.

2. How Does the Calculator Work?

The calculator uses the following equation:

Where:

• \( Ah \) — Required battery capacity in amp-hours
• \( VA \) — Volt-ampere rating of the alarm system
• \( h \) — Desired backup time in hours
• \( V \) — Inverter voltage (typically 12V or 24V)

Explanation: The equation calculates the battery capacity needed to sustain the alarm load for the specified duration considering the inverter's voltage.

3. Importance of Proper Battery Sizing

Details: Correct battery sizing ensures your intruder alarm system will function during power outages for the required duration without over-sizing the battery, which increases cost and space requirements.

4. Using the Calculator

Tips: Enter the alarm system's VA rating, desired backup time in hours, and inverter voltage (typically 12V for small systems). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between VA and watts?
A: VA (volt-amps) accounts for apparent power including reactive components, while watts measure real power. For alarm systems, they're often nearly equal.

Q2: How much extra capacity should I add?
A: It's recommended to add 20-30% extra capacity to account for battery aging and efficiency losses.

Q3: What inverter voltage should I use?
A: Most small alarm systems use 12V inverters, while larger systems may use 24V or 48V.

Q4: How does temperature affect battery sizing?
A: Cold temperatures reduce battery capacity. In cold climates, increase calculated size by 20-50%.

Q5: Should I consider battery depth of discharge?
A: Yes, lead-acid batteries shouldn't regularly discharge below 50% capacity, so you may need to double the calculated size.