Cambodian Cultural Exchange

We visited Chom Bok Primary School with the St Andrew's Youth Team for an early Easter Celebration.

A visit to the hot spring in Chom Bok.

At the PKH Aoral, there are interaction between the local students and us.



Benji, PKH Aoral Prince



Their local vegetable ferns.

For the hot weather at night, a cool wind from the computer fan helps alot to sleep at night!



A 80W Photovoltaic System with a 300W Inverter

We have installed a stand alone Photovoltaic System comprising of:
1. 80W Solar Panel
2. Charge Controller 12Vdc 5A
3. MCB Isolators for Solar, Battery and Inverter
4. 300W Inverter Morningstar Pure Sinewave
5. Deep Cycle Lead Acid Battery 12Vdc 100AH

The system is placed in the PKH Aoral office to provide power for the notebook computer and printer during the office hours.

Repair of School Bell for PKH Aoral

The School Bell timer in April 2014 stopped working after it was installed in October 2013. The electronic clock was not counting, hence it was replace with a mechanical 24 hr timer. The mechanical timer is easy to program and can set many different timing for the bell to ring.



Donation of Tools & Equipments to PKH Aoral

In early March 2014, we shipped by cargo tools and equipment to PKH Aoral for the purpose of training the Industrial Skill students.

Upon arrival at Aoral, we did a stock check on all the donated items shipped to PKH, Aoral.

In summary, almost all the items were accounted for except for 1 set of the technical drawing geometry set and 1 ruler under stationery items were missing. Also for the mechanical plumbing there was an extra PVC reducer among the items.

Teaching of English and technical Drawing to PKH Students at Aoral

In April 2014, we went to PKH Aoral to teach the students from Domestic Housekeeping and Industrial Skill Training basic English lessons and Technical Drawing skills.

The industrial skill training students were very keen to learn and were very appreciative of our help to them.

The English lessons for the Domestic Housekeeping students were given individual attention as they were slower in learning the English lessons.

Maintenance of the Solar Lamp Post

During this trip to PKH Aoral, we have to replace all the sealed lead acid batteries and change the micro-controller software for the solar charging algorithm for all the solar lamp posts.

Last October 2013, we have installed the 20 solar lamp posts and they were operating as planned until 4 months later when each of the batteries began to have reduced battery storage capacity, i.e. the lamps only light up 3 hours each night before switching off.

We suspected the battery charging algorithm was programmed wrongly as we have performed a hard charging of 14.9Vdc to desulphate the battery and also the charging was under high operating temperature (about 40 degrees Celcius).

We replace it with a new charging algorithm with the maximum charging voltage capped at 14.3Vdc and also provide a shade over the battery box to prevent direct sunlight heating up the battery inside the box.

We hope that the new algorithm and shading for the battery will improved the performance of the solar lamp post and will work with minimum maintenance for the next 2 years.

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!