Batteries

Available technologies

Currently, PVsyst supports two battery technology classes: Lead-Acid and Lithium-Ion.

Other technologies possibly used in solar systems are not yet implemented, namely flow-batteries and super capacities. Nickel-cadmium are analogous to Lead-acid, but with specific behaviors; this technology is of marginal use in PV systems, and will probably not be implemented.

Battery descriptions in the help

Battery description and usage are extensively covered in this documentation at multiple locations:

• A full description of the elements of the model in the pages below (voltage, capacity, aging, etc.
• A description of how it is used in the simulation,
• A description of the dialog, and the procedure for defining a battery,
• A description of the technologies and their properties.

Model choice justification

We have developed a non-conventional battery model that avoids pitfalls found in many existing PV software packages: either extreme simplifications that lead to rough system evaluations, or overly adjusted models based on numerous interrelated parameters whose physical meaning is often unclear to users. Required parameters are rarely provided in datasheets or typically require complete measurements of each battery. We have therefore aimed to fulfill the following criteria:

• The model should be presented in a relatively simple manner, involving only "explicit" parameters specific to each battery: technology type, voltage, number of elements, nominal capacity, internal resistance, Faradic efficiency, and aging properties.
• Most of these parameters should be available from the detailed datasheets. Others are predefined, specific to each technology.
• But it should be sufficiently detailed to satisfy the needs of the simulation of the PV system, where the charging current is practically imposed by the solar generator. In particular, its behavior in voltage is crucial and difficult, as the voltage depends on the current, the state of charge and the temperature. It is important in the intermediate zone for the evaluation of the SOC, and should be realistic enough at the end of charge and discharge to make the controller operating correctly.
• Further, it will be important to be able to estimate the ageing and the possible maintenance imposed by the conditions of use.