AN interesting thing happened in the electrical industry when we first had the Eskom power cuts... there was a rapid rise in the sale of portable generators and there was an even more rapid rise in self-appointed experts who claimed to know about diesel generators or claimed to sell them at best prices.
The joke was that the ‘experts' did not, for example, know anything about the following:
The difference between kilowatts and kilovars;
- Power factor;
- Line droop;
- Cross current compensation;
- Fault level; and
- Voltage regulation.
It mattered not - they sold the equipment and now there are many sad clients out there wishing they had bought generators from established suppliers rather than the Wongkong Happy Generator Company.
The kind of people who established themselves as new experts on generators are typically the same as the crew who claimed to be experts when computers first came along. Relying on massive public demand and, with limited actual knowledge of their product (but a long list of promises), they sold equipment that they didn't fully understand to people who were looking for bargains.
Now we have a similar situation with some ‘experts' in the solar panel industry.
I have a little solar panel that is made in South Africa by SunToy. It has written on it: ‘2V 500mA 1.0W'. This means that it produces a current of 500mA (or 0.5A) at a voltage of 2V.
Since 2 x 0,5 = 1, one can figure, without much thought, that the rating of 1.0W means 1W.
Now, it so happens that we have tested this little panel and it produces the power claimed. Great stuff. But, conversely, I have a solar panel outside the office that has the following ratings stamped on it: ‘Max P 68W, Volts at Pmax 16,5V, Current at Pmax 4.1A, Short circuit current 5,1A, Open circuit voltage 23.1V.'
All well and good. Now 16,5 x 4,1 is more or less 68W. However, this panel is sold as being rated at 60W (not 68W) and it's supposed to be good for charging 12V batteries. However, in extensive tests on two of the panels we have never got more than 3A out of any of the panels, even on the brightest day.
This may be because we were told we had to buy a regulator for each panel to prevent overcharging the battery. The regulators were rubbish - the one regulator packed up after a few days and the second one three weeks later. I took my concerns to the person who had supplied the equipment, let's call him Steve.
I copied him on emails but there was no response. The point is that the information given on the rating plate of 4.1A at 16,6V seems to imply that at 12V the current will be about 3A - which is what we got - but this is not 60W.
The panels were due to go to a bush camp in the Okavango and so it was a good thing that I tested them. One thing is for sure - I'm not buying anything from Steve again.
The matter of the regulator still puzzles me. Car batteries have regulators to prevent overcharging and so the technology is not new. Yet it is sold as being the next latest thing. As I remember, a regulator works like this: If voltage on battery rises above 14V, disconnect from charger. If it falls below 12V, connect to charger. It is not rocket science. Naturally, there are much smarter regulators using pulse width modulation (PWM) technology and they make your battery last longer. But, the downside is that, in South Africa, lightning and electronics are poor bedfellows.
My suggestion is that if you are going to buy some solar stuff: (a) get it from a reputable supplier, and (b) ask to see a similar installation that has worked for a number of years.
I can see that, like the generator business, the industry is filling up with fast operators, so do take care.