Manufacturing - solar
In mid-2005, we purchased a used single panel photovoltaic system to power lights on a remote ranch. The controller did not work, so Steve decided to make a more reliable one. He was designing a new line of electronics kits at that time, so the goal was to come up with a controller that could do the job of expensive ones at a much lower price. The prototype controller that he made became the Cielo Azul Charge Controller (CACC) described below. It has been working flawlessly for two years at Rancho Jixhil with a 70 watt Siemens panel and a 12 volt truck battery. The battery was a year old when we bought the system, so we do not expect it to last much longer.
When we gain a better understanding of the market in the region, we intend to manufacture the CACC in Comitán. We are not aware of any other electronic assembly work in the region, so it will be interesting to be ploughing this new ground.
Technical Description of the Cielo Azul Charge Controller (CACC)
The cost of batteries is about 50% of the life-cycle cost of a photovoltaic (PV) system. This is because batteries have a shorter lifetime than the PV panel and must be replaced periodically, the time depending upon their type and the care they receive. But their useful lifetime can be prematurely shortened if they are not charged correctly or discharged too far. Thus the need for a charge controller, like the CACC.
Charging involves controlling the flow of electricity from the PV panel/s in such a way as to charge the battery as rapidly as possible, avoid overcharging it, and keep it in a fully charged state. The CACC accomplishes this by means of a three-stage charging algorithm, which tracks the chemical reactions taking place in the battery by measuring its voltage and temperature.
First stage: Bulk Charge
When the charge of a battery is low there is a lot of material available for the reactions to occur. In this stage the CACC passes the maximum current available to the battery.
Second stage: Absorption Charge
With increasing charge, less chemical material is available for the reaction in the battery. If charging continued at the maximum rate, the battery could overcharge, causing heating and gassing of the electrolyte. To match the reaction, the CACC limits the average charging current by means of pulse width modulation, or PWM.
Third stage: Float Charge
Once the battery is fully charged, the CACC continues to charge at a minimal rate to compensate for the self discharge of the battery.
The CACC also protects the battery from discharging too far, which can cause irreversible damage to the battery. If the battery voltage falls to a predetermined level, the CACC electronically disconnects the load from the battery.
Other features of the CACC include: