The Solar Panel
My solar panel experiments continue. The sun isn’t quite up to it yet – just as well because this gives me more personal energy to get things done. Here it is on the left, my nice 250w panel which outputs maybe 36v. I’ve yet to work out an inexpensive yet solid frame for it but at least I can experiment with the kit I have to go with it.
The panel will feed out to a pair of “buck convertors” (not seen here) which are able to put out 15 amps each at anything from the input voltage down. Because the panel regulator I have is designed to handle 24v systems (with solar panels up to 40v) or 12v systems (with solar panels up to 26v) it is not keen on the idea of powering a 12v system using a 36v panel… so I thought of another way…
One of the buck convertors will output something in the region of 24v for the solar regulator which then not only charges the battery but also takes charge of the load, making sure it disconnects if the battery gets really flat.
The other buck convertor will supply 12v directly to my office for charging stuff. The battery will do the same and diodes will separate them so that in the event of full sunlight, I can draw power straight off the solar cell rather than feeding it through the regulator system. Should the sunlight drop the battery of course will take over – hence making sure I squeeze every single drop out of the solar panel.
What you see in the image above is one of two 12v deep discharge leisure batteries, the regulator, a 500w sine wave convertor (240v output) and my meter showing the state of the battery which is clearly no-where near fully charged. This was born out by my attempt to use my 500w milk 240v frother which failed miserably as the battery voltage dropped below 12v. The controller is an MPPT T20 which has a quite comprehensive display. Despite using decent copper speaker wire, I think I need a dramatic thickening of the wire to lower losses.
The large panel, able to output up to 250w was in fact outputting nearer 20w at the time due partly to the angle and mostly due to the clouds!!!
Update 01/05/2016: Now if you are reading this and wondering about the cable – you are right – it is WAY too thin even though it is actually quite heavy cable. Armed with plenty of sunshine today, I attached my 500w mains milk frother to the 500w sine wave converter and ran that straight off the battery. The fully charged battery dropped to 12.1v under load but when I checked the red/black connections on the investor – it was down to 10.9v – so under a metre of that cable dropped over a volt!!! Time to re-think cable thicknesses.