# Solar power supply (MPPT)?

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#### froggy

##### Member level 5
mppt circuit

Does anyone have drawings for a solar panel power supply? I'm looking for a PSU that implements Maximum-Power-Point-Tracking (MPPT). I want to charge lead-acid cells.

/Froggy

#### froggy

##### Member level 5
mppt charger schematic

Thanks alot Hishamsaleh,
but what I specifically looking for is a schematic incorperating MPPT technique to maximize the power output from the panel(s). To my understanding, MPPT means that the voltage output from the panel is kept at the level where I*U peaks (Max watts), while at the same time providing the battery bank with a suitable voltage for charging without any significant conversion losses.

/Froggy

#### flatulent

mppt schematics

I once looked into this and found that these specialized circuits are never used on small solar stations because their efficiency being less than 100% eats up the gain from using the peak power from the solar array.

Commercial arrays are made (putting the right number of cells in series) to have the opitmum power output to a lead acid battery. The area you can improve things is to track the sun. The simplest part is to change the vertical angle of the array over the 12 months of the year to be square on to the sun. The hard part is changing the horizontal angle over the 12 hours of the day.

It is usually cheaper to buy more arrays than to make a horizontal servo system. Doing the vertical angle change by hand every month is worth the effort.

#### froggy

##### Member level 5
solar mppt

This is for a small application 25-200W (RV's, Boats etc).

I dont think what you say is correct, according to the specs on a few commersial products with MPPT, they claim the following:

Power Gain: 10-30% depending on battery status, and solarpanel output.
Efficency: >97%
Power consumption: <3mA @ 12V

#### electronrancher

simple mppt schematic

Here's an example of MPPT of a small solar cell. Andy Pang sells some hobby style solar cells if you need some.. http://home.ust.hk/~bcandyp/solar-kit.html

To understand MPPT, inspect how the Vout/Iout plots appear similar to bjt or mosfet - long saturation region followed by a dropoff to linear as the cell is loaded with heavier current. If you run a cell right at the edge of linear operation, that is MPPT.

Here is the example: I set up a small, panasonic 243318 under a lamp so it gave about 3v max with no load (Voc), and 1mA max output current short circuit (Isc).

Now sweep a load (50k pot) attached to the cell, and record Iout, Vout at several points. My graph appears similar to the normal saturation plot, but is pretty rough due to few points.. (sorry!) I estimated the linear region to be from about 2.92v to 0v, as my load sweeps from 300uA to 1mA.

I found MPPT at about 2v for this cell in this light. Take a look and let me know if you understand how to find it. The circuit to do so? Haha that is your puzzle! I say multiply Vcell * Iout, and sweep current from 0 to point of dropoff..

#### electronrancher

simple mppt charger schematic

actually, my plot severely underestimates the MPPT, but finds it at the right point (~2v). The approximation says 1.2mW, but the original measurements say up to 2mW for this tiny cell!

If I get a better load than a 50k, I will do a nice sweep but until then i think you get the picture.

#### Darth Murat

##### Newbie level 1
mppt and alternator

I am using mppt with fuel cells
can you give me equations for calculating the gain i have with a 5kW fuel cell

#### cyberrat

boost mppt schematic

Oh look!
another 1 word pointless post to try & increase post count!

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