Notes on Solar Panels
2 x 15 W solar panels bought at Rona on sale at $27. Included a 6A battery charger regulator.
For one panel, Typical performance in direct sunlight : 0.75 to 1.0 A into 12 V SLA battery when pointing directly at Sun. If the panel is inside, behind glass window in direct sunlight the current drops to 0.4 to 0.5 amperes. Under cloudy conditions: 0.15 to 0.20 A. In cloudy condition, the best orientation seems to be pointing straight up.
According to blogs, a 12 V nominal SLA (Sealed Lead Acid) battery reaches 12 V, open circuit, when about 1/2 charge is left. A full charge seems to take the voltage to 13 V. This value is probably determined by the charger controller. Immediately after charging the open-circuit voltage may be over 13 V but after a few minutes drops to around 12.6 V.
It’s possible to charge a 7 A⋅h SLA battery within a single sunny day if it starts at 12 V.
Note than an 1800 kW installation typically only reaches 1200 W maximum power in Vancouer BC. about 8000 kW.h per day on sunny days. (Enphase energy log) In Nov, Dec, Jan and Feb the output is quite low. In Mar through Oct performance is useful. Over all there’s about 4000 kW.h/day yearly avg
Double Panel Mount
Here’s a simple mount for both panels, connected in parallel. The azimuthal direction is always -180 degrees (due south). The elevation can be adjusted by moving the base farther or closer to the building wall. The sage will need to be trimmed in the near future to avoid cover the panels. The wires go into the garage where the charging station is.
The optimum elevation angle can be calculated using an on-line tool such as at Solar Calculator. The picture was taken on May 11 at about 16:00. You can see from the graph that the correct elevation angle should have been 40 degrees.
The “charging station” keeps the same crude motif as all other installations. I’ve rigged up a cheap ($10.80) digital voltmeter and a 1Ω resistor to provide a current monitor.
The following circuits can be used to monitor the current during charge and discharge using a simple digital panel meter. The author’s uniquely designed Battery Box combines both charging and discharging circuits as well as providing a watertight container for the battery.
Next: The Battery Box