Repair of the 1KW Photovoltaic System at Aoral

In early March 2014, it was reported that the 1 KW Photovoltaic System is unable to provide the 230Vac upply. The status indicator on the Charge Controller Phocos, 24Vdc 40A, shows load disconnect. Several attempts to reset the system and force the solar panels to charge the batteries were unsuccessful.

 

A Schematic of the 1KW Photovoltaic System is shown below.

After reaching PKH Aoral, I tried to troubleshoot the system. The voltage measurement across the battery of about 14Vdc instead of the usual 24Vdc. All the batteries were disconnected and the terminal voltage was measured again and each battery is about 7Vdc which means the batteries are all dead.

We drove down to Phnom Penh to buy 10 Deep Cycle Batteries costing about USD165 each. It took about a day journey to and fro Aoral.

 

I have replaced the Phocos Charge Controller with a Morningstar Prostar 30 Charge Controller. This controller has a built-in Multimeter which can display the Battery voltage, Solar Current and Load Current. I have replace all the 10 batteries and switched on the system. Within minutes the battery voltage dropped to low voltage, i.e. less than 23Vdc. I quickly switch off the system to prevent further discharging. Finally, I managed to locate the short circuit in the system. It is caused by the 24Vdc load wiring somewhere underground which powers the 24Vdc lamps. I completely removed the 24Vdc load from the system and reconnect the batteries again. This time the system seems to work fine without the fast discharge of the batteries but there is zero Solar Charging current. To troubleshoot the zero solar charging current, I climbed up the water tank where the solar panels are mounted and dismantle every solar panels connections to check the solar panel voltage under sunlight condition. The individual solar panel voltage are working fine with 18 Vdc and I reconnect them together to configure for 36 Vdc system and check the solar charging current. The charging current looks good and the fault might be due to bad electrical contacts in the solar connectors. Finally I switched on the inverter to check the output of the 230Vac. The system seems to be working fine.

A 3 day battery voltage measurements was done using a data logger with the results shown below. The batteries are behaving properly with solar charging and inverter load discharging.

In summary, a short circuit in the underground cable cause the 24Vdc load to drain completely the 10 batteries and cause them to die. The bad electrical connections on the solar panels connectors provided little charging current to the batteries. hence the multiple source of failures cause the system to be non operational for the past 1 month.

Question: Ever wondered how I manage to carry the battery?
Answer: It is a dummy battery, that is why it is so light!