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How to modify buck converter? -> fixed MPP!

Vi s

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Dec 6, 2020
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Warm greetings

I have not much experience nor knowledge about electronics so that's why I need and ask for some guidance and help from those who do!

There are three common manual- or fixed mpp modules available for purchase. sd30crma, CN3767, BQ24650. Problem with those is they are quite expensive.

I was wondering if there is a simple way to modify the HW-613, an highly efficient (96%, 22w stable output with heatsink!) and super affordable (10 times+ cheaper than the mpp modules listed above!) buck converter,..
IMG_20210111_203553.jpgIMG_20210111_203609.jpg

.. so that it holds the input panel voltage at mpp 18v for a 22v panel (add somewhere a trim resistors? Where?)? I am looking for a easy hardware solution.

Does anyone happen to know how to do that and could you kindly explain me how to do it exactly? Which parts (value of resistors... ) do I need to get for this little hack?

Much much appreciate your help!
 
Last edited:
:)

Funny, I've been doing some research about it also.

My end results:
If you want cheap, get an PWM solar charge controller, their efficiency isn't so bad.

MPPT..
Jeah, buck converter usually use PWM, and MY biggest issue where the watts...

I don't have 1 x 18v solar panel for 1 12v battery..
Using the smaller PCB's seem tempting.
I would end up placing lots and lots in parallel and serial to accommidate my power needs.
Where each is a potential point of failure.

For a really small setup, yeah, sure.
For $6 you get pre-build PWM solar charge controller..
Not much $$ to gain but doable.
 
:)

Funny, I've been doing some research about it also.

My end results:
If you want cheap, get an PWM solar charge controller, their efficiency isn't so bad.

MPPT..
Jeah, buck converter usually use PWM, and MY biggest issue where the watts...

I don't have 1 x 18v solar panel for 1 12v battery..
Using the smaller PCB's seem tempting.
I would end up placing lots and lots in parallel and serial to accommidate my power needs.
Where each is a potential point of failure.

For a really small setup, yeah, sure.
For $6 you get pre-build PWM solar charge controller..
Not much $$ to gain but doable.
?

The author from the following thread https://diysolarforum.com/threads/soft-power-micropower-version-for-panels-21w.16473/ succeeded through the ingenious technique of current injection! Explained here in his github

Btw he also hijacked a 300w buck converter!

Further he mentioned if you need more than that better buy a commercial product.

I am ardently following and attempting to rebuild his soft power device with zero pre knowledge about arduino etc.. While following that path I was wondering if there is also an even easier way!? I mean on those above mentioned mpp scc's you can set the mpp via soldering a smd resistor or turning a trim resistor. So I thought maybe someone knows a hardware hack to set mpp on any buck converter!? ?
 
Those pwm chargers are no suitable option for me since I switched to lifepo4s and like to cycle between 10 to 90% at most. I actually already have such a pwm charger but they are pretty big and junky, I look for something small, to fit into my travel powerbox. Also my panel has only 20w so a 10A charger is overkill.

Your system (I read some of your posts previously) is a totally different ballgame!
?
 
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