MPPT on smaller panels

[chandana]

hi
i have recently conducted some experiments on  10W panel -12,7Ah battery system.it turned out that the MPPT  we were using did not improve the efficiency of the panel ,on the contrary the current flowing into the battery was lesser compared to system without MPPT at the same solar radiation level and battery voltage.we found that it was not adding any value to this panel battery system.
now my question is -Has anybody have any idea of "why the mppt failed to perform its intented task on 10W panel."..what could be the possible reason??...is there any problem with the algorithm or MPPTs simply do not work on smaller panels.....

[bob g]

nothing including mppt units is 100% efficient

some of the best are reported to be ~96 percent, so

with only 10watts of available power you likely are not making enough power to offset the overhead of the
mppt controller.

iirc you will need to have two things before they start to really come into their own,

1. you need much higher voltage than your battery, so if you have a 12volt battery you will need probably 40 or more volts
coming off the panels, and

2. you will need at least a couple hundred watts of panels catching sunlight

most mppt controllers work best on 24 and 48volt batteries with a few hundred watts of panels running between 40 or 50 volts up to
well over a hundred volts.  they need the differential to work with and they need enough watts in panels to have enough power to work with.

10 watts is just too anemic in my opinion

bob g

[ghurd]

What he said.

10W panel makes about 600ma?
And the MPPT controller uses 250ma?  500ma?  There just is not much power left to go to the battery.
With 20W of panel, the MPPT uses about the same power, so a much higher percentage of the additional solar power will go into the battery.

It is possible to get a decent gain with even a 40W 12V panel, but it is not likely to be economically sensible.
G-

[XeonPony]

Being I run an mppt set up I think I can say that  you need a higher voltage then the batteries as stated by the others, the peak for the one I use is 17V mp,  22V Voc, You need at least 30 to 60 watts befor you gain any advantage.

I run my system at 49V Voc, 32V Mp, and my aray is rated at 120W but actual wattage is average 75 to 90w (Wich is about expected for my area)

[Opera House]

I posted a while ago a small one using a 34063 that was used on a 6V 3W and a reject  12V 3W ( power point was about 8V) in series.  Together the best power point was about 21V 2.8W into a 12V battery.  I had added an extra transistor so it would turn off below the power point or above a certain battery voltage.  Pretty efficient 85% but major function was a regulator.  You don't really gain till the input voltage gets above 23V.