Solar Energy for My Lab

Use a reclaimed electric car battery to store solar energy for my lab

Solar power using mainly standard and recycled components.
I use a reclaimed electric car battery to store solar energy.
For the moment my main work is developing a stepup converter that can handle several 100W, to charge the battery. It incudes an MPP tracker.

I describe my progress in a blog (in German) on my GitHub Repository.
A Raspi Pico plays an important role in the control of the stepup converter.

Project Elements

SolarPower-main.zip (ZIP)

Discussie (3 opmerking(en))

Mat Barley 1 jaar geleden

very interesting. But before I get deeper into it and then finally failing at the very beginning, my question: How to get a used car battery??

Antwoord

Jean-Claude Feltes 1 jaar geleden

Oh, that was not my decision. One morning our car refused to drive. The garage's verdict was that we had to change the battery. I insisted to get the old one and there I was, with a battery that wanted to be used somehow.
It took me quite a long time before I really started with the project, I knew that it would take very much time and effort. But also that I would learn a lot!

The first tests showed that the battery was not "dead", but could deliver some tenths of Amps without shivering.
I wondered if it had been a software problem, instead of a battery problem. I don't know.

My first concern was about a battery management system, you can see my work on this here:
https://github.com/jean-claudeF/BMS
There were some problems that I thought I would resolve later, so for the moment I go without BMS.
However I control the cell voltages irregularly, until now they were OK. I thought maybe the BMS was not absolutely necessary at the beginning, as the currents are low in comparison to the electric car. Later I will se...

There is surely much space for improvements. I wanted to have something working to start with, even if it is far from perfect.

Please note that all of this is work in progress and not a readymade solution!

Antwoord

Emil Almberg 1 jaar geleden

Why are you asking about car batteries?
It is the worst choice for storing energy for solar systems.
If you have them, it's a better deal to sell them as scrap (you get money for them), and buy new ones made for the purpose, either lead or lithium,

Antwoord

Deltor 1 jaar geleden

### EDITED. Comments that are against the rules will be edited or deleted. ###
Someone deleted my comment to that question/comment of "Emil Almberg".
My comment remains:

Waste++

Sell and scrapping almost new cells and buying new ones - that's ridiculous and brain-dead!

Antwoord

Deltor 1 jaar geleden

So, und jetzt hat also ein Kasper sein fettes EDITED reingeschissen, weil ihm mein Kommentar über diesen Idioten, der meinen _berechtigten_ Kommentar ungefragt still und (vermeintlich) heimlich gelöscht hatte, nicht passte.
Ich muss ja zugeben: das "Arschloch" war unangemessen, Arschlöcher sind schließlich unabdingbare, wertvolle Körperteile.
Dieser Idiot, der meinen Kommentar gelöscht hatte, ist weder wertvoll noch unabdingbar.
Ich hoffe, dass der Heini wenigstens mit einem kräftigen Tritt in sein wertvollstes Körperteil (Rectum) aus der Liste der Löschungsberechtigten rausgekantet wurde!

Dabei stellt sich mir die (Gretchen-)Frage:
Wie hält's eigentlich die Redaktion mit der Nachhaltigkeit?
Das kann ja wohl nicht angehen, dass sich heutzutage jemand wie dieser Emil Almberg die geistlose Blöße gibt und in solchen Foren seinen mentalen Stuhlgang zur vermehrten Verschwendung von Rohstoffen ungestraft zum Schlechten gibt.

Antwoord

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2 Opmerking(en)

Jean-Claude Feltes 1 jaar geleden

Everything I have is on Github:
https://github.com/jean-claudeF/SolarPower

For the moment the accent is on a stepup converter that is used to load a LiIon BMWi3 battery.
The circuit you see on the image is capable of handling 500W to the battery.

A blog in German on this development is also on Github:
https://github.com/jean-claudeF/SolarPower/blob/main/Stepup_solar_blog.pdf

Antwoord

Deltor 1 jaar geleden

Since you already abuse a MOSFET as a diode, have you ever thought of using the unused high-side driver part of the IR2101 to implement a synchronous converter?
Well, I think so! :-)
If you use an IR2104 instead of an IR2101 there is no need for further devices at all (*): simply connect the collector of your 54V emergency shutdown circuitry transistor to the SD input of the driver IC, tie the collector resistor to VCC instead the PWM signal and connect your PWM signal to the driver IC's IN input.
(*) OK, probably you may want to use a gate resistor for your high-side MOSFET. ;-)

Hah, forgot to mention: you will have to invert the phase of your PWM signal!!!

Sorry, I forgot another thing: the bootstrap diode and the related capacitor for the high side of course. ;-)

Regards!

Antwoord

Jean-Claude Feltes 1 jaar geleden

Yes, I thought about it.
But as there are so many things to think about on this project, I wanted to start with somethin simple and robust.
Thanks for your ideas, I will come back to them.
For the moment I am struggling with an uncertain WLAN / MQTT connection to homeassistant, that takes a lot of time!

Antwoord

Deltor 1 jaar geleden

The IRS2184 has higher output drive capability (1.4A source, 1.8A sink, minimum!) than the IR2104 and a bit shorter dead time (400ns), so the MOSFETs will switch faster and - probably - more efficiently.
But, be warned: the pinout is different!

Cheers!

Antwoord

Jean-Claude Feltes 1 jaar geleden

Oh yes, more driver current would reduce the switching losses.

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Murat TA1DB 1 jaar geleden

Hello Jean-Claude,

I translated your blog into English with help of google translate as attached.

I am very much interested in this topic; in addition to what you're doing I plan to work on a) a bi-directional inverter / converter for feeding power back to the grid when necessary and/or asked, b) a fast power outage sense circuit for fast power-line islanding in case of grid failures; I would welcome very much your comments in these details if any.

Regards,
Murat

Stepup_solar_blog_english.pdf (2456kb)

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Jean-Claude Feltes 1 jaar geleden

Thanks Murat!
I had a short look at the translation, it is "Google style", but probably you can read it.
If I were to start again, I would write it directly in English. But German comes a bit more fluently for me.

Please tell us more about your project as soon as you have something to show.

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Content Director, Elektor 1 jaar geleden

We'd like to know more about your solar project. Can you post some additional details here, such as a more in-depth description and perhaps some diagrams and/or schematic?

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