Calculate How Many Batteries are Needed for the BP52

Calculate the number of VBX batteries needed to provide the desired runtime in the event of a power outage

The VBX series is an advanced backup battery system for the BP52 Alarm panel. VBX batteries utilize lithium iron phosphate (LiFePO4) chemistry, which significantly outperforms traditional sealed lead acid (SLA) batteries in terms of lifespan and energy capacity.

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How many batteries do I need?

The BP52 has two integrated battery slots and supports up to two external dual battery enclosures, allowing for a total of six 200Wh batteries. To calculate the backup capacity needed for your system, add the power of all high-load devices connected to your system and multiply this number by the number of hours of backup time required.

Divide the battery capacity needed by the capacity of the ACC-VBX-200WH battery to determine the number of batteries needed:

# of Batteries Needed = K / 200Wh

Examples of connected devices and their power consumption are provided below:

A = 8.5W (panel idle mode)

B = 0.5W (cellular backup average power consumption)

C = 3W (expander average power consumption)

D = 4W (keypad average power consumption)

E = 6W (Security Camera - day mode average power consumption)

F = 10W (Security Camera - night mode average power consumption)

G = 8W (Intercom average power consumption)

H (Total power) = A + B+ C*(# expanders) + D*(# keypads) + E*(# Cameras) + F*(# Cameras) + G*(# intercoms)

J = hours of backup you need

K (battery capacity needed)= H*J

Example: A site with a panel, cellular backup, two keypads, an expander, and two cameras can typically run for 12 hours with two VBX batteries.

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Battery capacity vs temperature

A battery’s capacity is not impacted by higher operating temperatures, but batteries operating at lower ambient temperatures have reduced capacity.

Subtract 1% capacity for every degree operating ambient temperature below 20°C.

Example: Operating temperature is 10°C

Battery capacity is [100% - (20-10)%] * 200Wh

= 90% * 200Wh

= 180Wh

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Recharge Time

A minimum system power of 20W is allocated to battery charging - though more power is made available to charge batteries if system loading allows.

Assuming a minimum charge power of 20W, a fully depleted battery will recharge in approximately 10 hours. Multiply 10 hours by the number of installed batteries for the time to completely recharge all batteries.

Example: The panel operates at maximum load, and only 20W is available for charging. AC power is restored just before the four connected batteries are completely depleted.

Recharge time = 10h *4 batteries = 40h

A maximum system power of 90W is allocated to battery charging, which may be divided between all connected batteries up to a maximum of 40W per connected pack

At maximum charge power, a fully depleted battery will recharge in approximately five hours.