The main technical measures of a Battery Energy Storage System (BESS) include:

Energy Capacity

The term energy capacity refers to the amount of energy that the battery can store, typically measured in kilowatt-hours (kWh).

Power Rating

Power Rating refers to the maximum amount of power that the battery can deliver or absorb, typically measured in kilowatts (kW).

Efficiency

Efficiency refers to the percentage of energy that is converted from one form to another without being lost as heat. The efficiency of a BESS is typically measured as a percentage and can vary depending on the charge and discharge state of the battery.

Round-trip Efficiency

This refers to the percentage of energy that is stored in the battery and then retrieved, taking into account any losses that occur during charging, discharging, and transmission.

Cycle Life

This term refers to the number of times that the battery can be charged and discharged before its performance degrades significantly.

Self-discharge Rate

The self-discharge rate is the rate at which a battery loses its charge when not in use.

Temperature Range 

This refers to the range of temperatures within which the battery can operate safely and efficiently.

Voltage Range

This refers to the range of voltage within which the battery can operate safely and efficiently.

Power/Energy Density

This refers to the amount of power/energy that can be stored in a given volume of the battery.

These technical measures are important for evaluating the performance and suitability of a BESS for a particular application, and they are often used to compare different battery storage technologies.

C-Rate

The C-rate of a Battery Energy Storage System (BESS) is a measure of the rate at which energy is being charged into or discharged from the battery. It is defined as the ratio of the current flowing into or out of the battery to the capacity of the battery. The unit of C-rate is commonly expressed as "C", where 1C is equal to the capacity of the battery.

For example, if a battery has a capacity of 100 kWh and is being charged or discharged at a rate of 100 kW, the C-rate is 1C. This means that the battery is being charged or discharged at its maximum rate.

A higher C-rate means that the battery is being charged or discharged at a faster rate and can result in a shorter charging or discharging time. However, it also means that the battery is under more stress and can result in a shorter lifespan.

A lower C-rate means that the battery is being charged or discharged at a slower rate and can result in a longer charging or discharging time. This also means that the battery is under less stress and can result in a longer lifespan.

It is worth noting that different battery technologies have different C-rate capabilities, for example, a lithium-ion battery can handle higher C-rates than a lead-acid battery, but also have different optimal charging and discharging rates.

Also, depending on the specific use case, different C-rate may be required, for example, in a grid-scale storage, a low C-rate may be more suitable, while in electric vehicle charging a high C-rate is desirable.