Solar

Basic information about solar node can be found on its web page?. There is also documentation describing the whole project (in Slovenian). This page presents interaction of solar node with the nodewatcher? system used in wlan ljubljana network.

As it can be seen on node's nodewatcher page nodewatcher also collects data from the solar regulator powering the node. Node is using PL20 regulator from ​Plasmatronics which has serial port interface to interact with it. Connecting this to node's Linksys router? we can retrieve data from the regulator using open source interface we have developed. As nodewatcher uses simple way of communicating we can feed additional data to node's data feed which is collected by monitoring daemon and then displayed on the web interface.

We measure and collect battery and solar panel voltage and charge and load current. We also monitor in which state of charging the regulator is (from ​regulator's manual):

• Boost: In the boost stage all the charge current available is used to charge the battery. As the battery charges, its voltage rises. When the voltage reaches the boost maximum voltage and remains there for 3 minutes, the controller will automatically advance to the absorption stage.
• Equalize: Many battery manufacturers recommend that the battery bank be given an overcharge occasionally. The equalise state is designed to equalise the voltages and specific gravities of all the cells in the bank by bringing them all up to full charge and stirring up the electrolyte in the liquid cells by gassing to reduce stratification.
• Absorption: In absorption state the regulator tries to keep the battery voltage constant while the last part of the battery charging occurs. This prevents excessive gassing which occurs at high cell voltages. The regulator will keep the battery voltage at the absorption voltage until it has been at this voltage for the absorption time. If there is a cloudy period and there is insufficient charge current to keep the voltage up to the absorption voltage, then the absorption timer will stop and resume when the voltage comes back up to the absorption voltage. When the absorption time is finished, the regulator advances to the float state.
• Float: In the float state the battery has been fully charged. The charge current is now used to keep the battery voltage at a level which maintains full charge. This voltage should be below the gassing voltage to avoid excessive electrolyte loss. If charge is drawn from the battery, the regulator will allow charging to resume until the battery returns to float voltage.