Being pretty new to this forum I've been going through previous threads looking for stuff of interest. A subject that caught my eye was MPPT and I think I have now read all previous threads relating to it, but they all seem to have peetered out.
I think "Dippy" mentioned starting thread to explain his experiments with MPPT, I look forward to seeing that.
"Adiman" seems to have a very good working unit. see...
http://www.picaxeforum.co.uk/showthread.php?t=9816&highlight=mppt post19
BB's Switchmode Charger thread was very informative, although this paragraph has me a bit puzzled...
I would like to have a go at a Picaxe based MPPT when I have collected enough information. I realise that an extra panel would give much more than a MPPT would but it wouldn't be as interesting a project. I did design a 20 amp 24v to 12v converter based on a switcher about 20 years ago.
I don't mind re-inventing the wheel or trying to improve or build on someone elses, so if there are any ideas out there maybe this thread can be the start
I think "Dippy" mentioned starting thread to explain his experiments with MPPT, I look forward to seeing that.
"Adiman" seems to have a very good working unit. see...
http://www.picaxeforum.co.uk/showthread.php?t=9816&highlight=mppt post19
BB's Switchmode Charger thread was very informative, although this paragraph has me a bit puzzled...
I would have thought that to adjust the duty cycle of the converter to get the best position on "the hill" curve for maximum power out would not have needed such a fine adjustment as less than 1%? Looking at the curve of my solar panels, I have 2 X 64 watt Unisolar on the roof of our motorhome, its very rounded and would have thought that a few % either way wouldn't make too much difference at the peak. I also thought that the curve would remain a similar shape but in a different position under different light conditions. If I've missed the point could you explain this to me please BB.I don't have the ACTUAL numbers to hand that came from my results but this example explains the problem.
Suppose that a duty of 30% makes the MPPT run at it's optimum. Let's say about 80% efficient.
A duty of 29% would hardly load the panel at all and efficiency would drop off dramatically. A duty of 31% would excessively load the panel again resulting in a MASSIVE drop in efficiency. Now let's say the battery gains a little charge and the optimum duty would be 30.01%. Running at 30% would only give about 50% efficiency and running at 31% would give only about 30% efficiency. The PICAXE is simply not capable of running at the required duty to give a better efficiency than just connecting the panel direct.
I would like to have a go at a Picaxe based MPPT when I have collected enough information. I realise that an extra panel would give much more than a MPPT would but it wouldn't be as interesting a project. I did design a 20 amp 24v to 12v converter based on a switcher about 20 years ago.
I don't mind re-inventing the wheel or trying to improve or build on someone elses, so if there are any ideas out there maybe this thread can be the start