control the entire energy flow in solar home systems
As a central control element in off-grid photovoltaic systems, Steca solar charge controllers control the entire energy flow while ensuring optimal battery maintenance. The products developed and manufactured by Steca ensure extremely low costs due to their long service lives. Steca solar charge controllers and sine wave inverters are the best choice for a modern and professional power supply – all over the world.
General recommendations for the selection of the solar charge controller
The solar charge controller is the central component of an island system. It regulates the energy flow in the entire system and is decisive for its function and service life. A suitable solar charge controller must therefore be carefully selected. The cost share of the solar charge controller measured against the total costs of an island system is only 3 to 5 %. However, it is the most important component for the system. A high-quality and reliable solar charge controller of a higher price class pays for itself very quickly, as it contributes significantly to a long battery life and thus significantly reduces the overall costs of the system.
Selection of topology
Steca solar charge controllers are available as professional hybrid shunt controllers, as serial charge controllers or as MPP trackers. Depending on the requirements of the application, the appropriate topology should be selected. Switching charge controllers such as shunt and serial charge controllers can only be used for 12 V systems in conjunction with 36 cell solar modules. For 24 V or 48 V systems, two 36 cell (24 V) or two 72 cell (48 V) solar modules must be connected in series to form a string. Serial charge controllers are well suited for small applications and solar home systems. For larger applications and hybrid systems, shunt controllers are recommended as they have a lower power dissipation when charging. Due to their good electromagnetic compatibility, shunt controllers are also recommended for telecommunications applications. A solar charge controller with MPP tracking must be used if solar modules that are not made up of 36 or 72 cells are used. This includes most solar modules optimized for grid-connected systems and all thin-film modules. The lower the average annual temperature and the more important efficient charging is at low battery levels, the more advisable it is to use an MPP tracker, even if 36-cell standard modules are used.
Design of the solar charge controller
When designing switching charge controllers, the short-circuit current (Isc) of the solar modules is the decisive factor (under STC conditions). Steca generally recommends designing the solar charge controller generously. The nominal current of the solar charge controller should be approx. 20 % above the sum of the short-circuit current of all connected solar modules.
If the solar charge controller is used in an application in which people live with the system, it is important that it has a large LC display that shows the operating states via symbols. The solar charge controller should be equipped with an integrated energy meter to inform the user about the system and how it is used. For purely technical applications, such as night light systems, a solar charge controller with a simple LED display is sufficient.
Cables and construction
In order to ensure a long service life, it is important to use solid solar charge controllers and connect them to the battery via short, thick cables. The device should always be screwed directly above the battery to a non-combustible wall. It is important that there is enough free space around the solar charge controller so that it can be sufficiently cooled by the ambient air. In any case, the regulations in the operating instructions must be observed.
In applications with stand-alone inverters or in hybrid systems, it makes sense to use solar charge controllers with additional functions. A connection possibility to the stand-alone inverters for communication and coordination of the devices is a prerequisite for an effective inverter or hybrid system. Furthermore, special functions for energy management are of central importance for hybrid systems.