CALCULATION
Overview
Challenge
A battery sizing study is used to determine the parameters of a backup power system that ensures operation of critical loads in case of loss of external power supply.
It allows to:
- determine required battery capacity
- ensure required autonomy time
- select battery type and configuration
- verify correct operation of the DC supply system
What it means
In case of loss of main power supply, the battery becomes the only source of power for:
- protection systems
- control and communication systems
- circuit breaker control circuits
- signaling systems
At this moment, it is critical that the battery:
- has sufficient capacity
- maintains operation for the required duration
- provides stable voltage
In practical terms, this study ensures that protection and control systems remain operational even during complete power loss.
Applications
- design of substations and switchgear
- DC system design
- modernization of existing systems
- battery replacement projects
- verification of existing battery capacity
- compliance with regulatory requirements
Conditions Considered
The study may include:
- normal operation (battery charging mode)
- discharge during loss of supply
- transient conditions during switching
- peak load conditions
Parameters Analyzed
- total DC load demand
- required autonomy time
- battery voltage and its variation over time
- charge and discharge currents
- temperature impact on battery capacity
- operating conditions
When the Study is Required
- during design of new facilities
- when replacing batteries
- when increasing DC load demand
- when changing autonomy time requirements
- when verifying existing systems
- when ensuring compliance with applicable standards
What the Study Provides
A battery sizing study allows to:
- determine adequacy of battery capacity
- identify unacceptable voltage drops
- verify compliance with autonomy requirements
- select optimal battery type
- determine the need for battery upgrade or replacement
- justify charger parameters
Deliverables
The final report includes:
- battery capacity calculation
- battery type and configuration selection
- charge and discharge analysis
- conclusions and recommendations for equipment selection and operation
Customer Value
- reliable supply of critical systems
- reduced risk of protection and control failure
- correct selection of batteries and chargers
- compliance with standards
- improved operational reliability
Why it matters
During a power outage, loss of supply is immediate, but system control must continue to operate.
If the battery system is incorrectly sized:
- protection may fail
- circuit breakers may not operate
- control systems may shut down
This study ensures that critical systems remain operational under all conditions.
Input data
- DC system configuration
- List and power of connected loads
- Load operating profiles
- Required autonomy time
- Charger parameters
- Battery types and characteristics
- Operating conditions (temperature, duty cycle)
- Applicable standards and requirements
Results
- Determination of required battery capacity
- Selection of battery type
- Calculation of charge and discharge currents
- Definition of battery configuration and number of cells
- Verification of operating conditions
- Recommendations for charger selection
- Recommendations for installation and operation