Camera Backup Battery Calculator
What the Camera Backup Battery Calculator does
The Camera Backup Battery Calculator estimates the nominal battery energy needed to keep a camera system running during a power outage. It combines the power used by your backup-connected equipment with your desired runtime, then adjusts the estimate for power conversion losses and the portion of battery capacity you expect to use.
The result, labeled Required Battery Capacity, is shown in watt-hours (Wh). Use it as a starting point when comparing batteries or backup power systems. Choose an available capacity at or above the result, and consider adding a margin for conditions that can reduce runtime.
For readers of thebestsecuritycameras.com, the important first step is to think beyond the cameras themselves. A security system may also need a network video recorder (NVR), digital video recorder (DVR), Power over Ethernet (PoE) switch, router, modem, or other equipment to stay useful during an outage. Include the power draw of every device that will be connected to the backup and needs to remain on.
The calculator assumes that the combined equipment draws a constant average power throughout the outage. Its default values are illustrative, and actual runtime will vary with the equipment, battery, and backup system.
How to use the Camera Backup Battery Calculator
Enter the following four values to estimate the battery capacity your camera system needs:
- Total backup system power (W): Enter the combined average power draw, in watts, of all equipment that must remain on. The calculator accepts values from 1 to 5,000 W.
- Desired backup time (hours): Enter how long you want the equipment to run during an outage. The available range is 0.5 to 168 hours, in half-hour increments.
- Power conversion efficiency (%): Enter your estimated efficiency for delivering battery energy to the equipment. The calculator accepts 50% to 100%.
- Usable battery capacity (%): Enter the percentage of the battery’s nominal capacity that you expect to use. The calculator accepts 50% to 100%.
To estimate total backup system power, add the wattage of each device that will be powered by the backup. Equipment labels and manufacturer specifications can help, although a measured average under representative operating conditions may give you a more useful input. Make sure your total reflects the setup you expect to use during an outage.
For example, if your backup must power cameras through a PoE switch as well as an NVR, account for the complete connected load. If remote access is essential, include any router and modem that must remain powered too. A camera may still record locally when internet service is unavailable, but remote viewing depends on the rest of the connection working.
How the Camera Backup Battery Calculator formula works
The calculation starts with a basic energy relationship:
Equipment energy needed (Wh) = total backup system power (W) × desired backup time (hours)
It then adjusts that energy for conversion efficiency and usable battery capacity. Since both inputs are entered as percentages, the calculator uses this formula:
Required Battery Capacity (Wh) = power (W) × time (hours) × 10,000 ÷ (conversion efficiency (%) × usable battery capacity (%))
The adjustment makes the nominal capacity estimate larger than the energy the equipment consumes. For example, a backup system with an assumed 85% conversion efficiency does not deliver every watt-hour stored in the battery to the connected devices. Similarly, an assumed 80% usable capacity means the calculation reserves part of the battery’s nominal capacity.
Worked example using the default values
Suppose a camera system and its supporting equipment use a combined 32 W, and you want them to run for 8 hours. Assume 85% power conversion efficiency and 80% usable battery capacity. These percentages are illustrative assumptions, not guaranteed characteristics of a particular backup system.
- Calculate the equipment’s energy requirement: 32 W × 8 hours = 256 Wh.
- Adjust for the assumed conversion efficiency and usable capacity: 256 Wh ÷ (0.85 × 0.80).
- The estimated Required Battery Capacity is 376.47 Wh.
In this example, look for a compatible battery with at least 376.47 Wh of nominal capacity and round up to an available size. A larger margin may be appropriate because actual load, battery condition, temperature, and conversion losses can differ from the assumptions.
Use cases for the Camera Backup Battery Calculator
The calculator can help you compare backup needs for several common security setups:
- Home security cameras: Estimate the capacity needed to keep cameras and a recorder operating through a short outage.
- PoE camera systems: Include the PoE switch or other power equipment and connected devices that must continue running.
- Small business surveillance: Compare the battery energy needed for different outage durations when keeping a recorder and network equipment online.
- Remote viewing setups: Include the router, modem, and other required network devices when planning for access away from the property.
- Backup planning comparisons: Change the desired backup time or assumed efficiency to see how each affects the estimated nominal capacity.
For a more focused estimate, decide which functions matter during an outage. A system intended only to record locally may have different power needs from one that must also support remote alerts and live viewing. Only include devices that will actually be connected to the backup and need to operate.
Other factors to consider when calculating Required Battery Capacity
Changing power draw: Cameras and recorders do not necessarily use the same amount of power at all times. Night vision, recording activity, network traffic, and other operating conditions can change the load. The calculator uses one constant average, so an input based on only a quiet daytime period may underestimate energy needs.
Battery aging and temperature: A battery’s available capacity can change as it ages and can be affected by temperature. The calculation does not separately model those effects. Allowing extra capacity can help accommodate uncertainty, especially when a particular runtime is important.
Discharge rate: Available energy and runtime can also depend on how quickly a battery is discharged. Check the battery and backup system specifications for your expected load rather than assuming the nominal watt-hour rating will always be available under every condition.
Voltage and power output: Watt-hours describe energy capacity, but capacity alone does not establish compatibility. The battery and backup equipment must support the required voltage and provide enough power for the connected devices. Check the equipment specifications, including any applicable startup requirements.
Efficiency and usable capacity assumptions: The 85% efficiency and 80% usable capacity defaults are examples. Use estimates appropriate to the battery, converter, and backup arrangement you are considering. Lower assumptions increase the calculated nominal capacity; higher assumptions reduce it. Entering 100% for either value assumes no loss or reserve for that part of the calculation.
Internet and recording dependencies: Battery power cannot guarantee that an internet provider’s network will remain available. Check how your cameras and recorder behave when the local network or internet connection is interrupted, and include any equipment needed for the functions you want to preserve.
Camera Backup Battery Calculator FAQ
What does a watt-hour mean for a camera backup battery?
A watt-hour measures energy. A device drawing an average of 32 W for 8 hours uses 256 Wh before accounting for losses. A battery’s nominal watt-hour rating describes its stated energy capacity; the energy available to your equipment can be lower because of conversion losses and limits on usable capacity.
Should I include the NVR and router in the power total?
Yes, if they need to remain on and will be connected to the backup. Include the cameras, recorder, network equipment, and any other required devices in the Total backup system power input. If remote viewing is required, consider the modem and any other equipment needed for that connection.
Why is the required battery capacity higher than watts multiplied by hours?
Watts multiplied by hours gives the energy the equipment is expected to consume. The calculator increases that figure to account for your entered conversion efficiency and usable battery capacity. With the default assumptions, only 68% of nominal capacity is represented as energy delivered to the load: 85% multiplied by 80%.
Will a 376.47 Wh battery always run the default system for eight hours?
No. The default result is an estimate based on a constant 32 W load, 85% conversion efficiency, and 80% usable capacity. Actual runtime can be shorter or longer as load, temperature, battery age, discharge rate, and losses change. Select a compatible available size at or above the estimate and consider an additional margin.
Can I use the result to compare batteries rated in amp-hours?
Yes, if you also know the battery’s nominal voltage. As a basic conversion, watt-hours = nominal volts × amp-hours. Compare the resulting nominal watt-hours with the calculator’s estimate, while checking that the battery voltage and backup equipment are compatible with your camera system.