Hi,
With solar panels, they can be safely shut off with no power output from the panels, without damaging the solar panels. So they do not require a diversion load.
With a wind system, if the battery gets full, then it can damage the wind machine if it is disconnected from the batteries and there is not another load on the wind machine, the machine will go over the rated speed, and damage itself. So a diversion load controller will put a load such as a 200 watt electric heater on the system to keep the wind machine from overspeeding.
With a solar system, you can install a diversion load system. This might include running a 12 volt electric element to warm hot water, or heat a compartment, or something else. Or run a bright light? However most solar systems just use a MPPT or PWM controller. This stands for Maximum Power Point Tracking or Pulse Width Modulation.
Pulse width modulation came first, it is basically a electronic way to turn on and off a relay, and they modulate the amperage by changing the time the charge from the solar panel is left on as the voltage reaches 13.5 volts. In other words, the width is full when the voltage is less than 13 volts, but as the voltage reaches 13.5, then the voltage is only left on for a fraction of a second at a time, as it reaches 13.6 volts then it is off more than on.
Maximum Power Point tracking does something else. A "12 volt" solar panel actually puts out 21.0 "Open Circuit" with no load on it. Under load, the panel can put out 18 volts X say 5 amps. This would be a total of 90 watts. The MPPT controller changes this to 6 or 6.5 amps then charges the 12 volt battery with more amperage than the solar panel is putting out. So the MPPT controller can put out more amperage if the battery is lower charge, so a depleted 12 volt battery that is at 11.7 volts will get even more amperage than a fully charged battery.
Personally I have a 50 amp MPPT controller, and 15 years ago it cost about $350. Now they are a little less expensive. If I would recommend one, it would be a pair of 10 or 20 amp PWM controllers. You can get them for only $20 now. A 100 to 120 watt 12 volt solar panel from this place.
SunElec.comI bought a 10 amp PWM controller from this website.
AliExpress.com Search for 10 amp PWM solar controller. Then search for "Price" lowest at the top, and it will give a huge list, with sale prices, starting with really low cost, say $8 for a lot of 100 ($800 for all of them) start looking for quantity of 1, and they should be about $15 with free shipping.
Fred.
