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Little solar powered battery and led.

Lziga55

Oct 2, 2023
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Hello, I'm Žiga, a student of electrical engineering. i decided to make a small off grid solar power plant with a 10w solar panel and 4 to 5 3000mAh li-ion batteries. I would use this as a power supply for a led strip with a consumption of up to 10W or 15W. so far I've done mostly arduino projects, such as the egg incubator. since I do not have much experience and knowledge about solar power plants, I am asking for your help in the implementation and composition of the project. I would probably use modules as that would be the cheapest and easiest. I mainly buy components from aliexpress. If you have any other ideas please let me know. But first, I should start by assembling the circuit. so far I've researched quite a few things about the operation, the bms for the battery, but I can't find out how to charge the batteries via solar cells. what module would you need for that...?!
please help and thank you
 

Externet

Aug 24, 2009
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Welcome.
'Little' means nothing; 10 to 15W may not be 'little' for many. 4 lithium cell if in series, can be around 12V to 16V depending on chemistry and the charge voltage should be not more than 14 / 16.8V for the group. BMS board should be used then, and the solar panel should be of a voltage that the BMS can manage. If li cells are in parallel for a parallel LED string, a solar panel should be of according voltage at full sun.

For charging a cell to 4.200V, a solar panel of 5V (10 cells) is fine connected with a silicon diode to drop the excess voltage. No charging management board added.
Solar panels are current sources, not voltage supplies. Their behavior is they present their voltage of around 0.5V per series cell as soon as some light hits them with no load. The open-circuit voltage is present with little change at varying light levels. When sunny, their voltage does not drop with a proper matched load, it is then capable to push current to a load with stable voltage.

(-)----------------(-)5V solar panel(+)-------------|>|---------------(+)Li cell(-)-----------------(-)

Feeding the LEDs is just taken from the cell above, not drawn.
 
Last edited:

Alec_t

Jul 7, 2015
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Welcome to maker.pro!
A 10W solar panel is never going to power a 15W LED strip, nor even a 10W one on a cloudy day.
You need a dedicated charger module to suit the cell chemistry and the number of cells making up a battery.
Is this a school/college assignment?
 

Lziga55

Oct 2, 2023
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Welcome to maker.pro!
A 10W solar panel is never going to power a 15W LED strip, nor even a 10W one on a cloudy day.
You need a dedicated charger module to suit the cell chemistry and the number of cells making up a battery.
Is this a school/college assignment?
Hi, so we have a small old house without electricity. It is on top of the hill and its always sunny there. I need light there like once a month so I tought that 10w solar panel and 50Wh battery would be enaugh. And 9W is 4 meters of my led strip so probably it will be enaugh.
Question. Dont i need some kind of over charging and discharrging protection.. I dont have any idea how to do it. I thought that i should bought 4s bms and connect batteries to it and than connect solar panel to it somehow but yes, I need constant voltage so I need something between that. Please correct me if I am wrong. And output probably is same as input voltage so i need regulator there too. Actualy this isnt school project, but maybe it will become school project ;) we need to make something in pairs or alone in school until january so maybe this will become school project or maybe it wont ;)

Thanks for help
 

Lziga55

Oct 2, 2023
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And I meant little electrarn as small. Sorry for my bad english.
 

Alec_t

Jul 7, 2015
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Dont i need some kind of over charging and discharrging protection.. I dont have any idea how to do it.
Buy a proper balanced charger. The BMS provides over-charging and over-discharging protection.
 

Lziga55

Oct 2, 2023
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Ok, if i use bms lets say 4s it needs 14 to 16 volts input for charging. How do i get constant voltage from solar panel?
 

Lziga55

Oct 2, 2023
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I have an idea but I dont know if it will work. Solar panel 12v -> dc to dc step up converter to 16v -> 4s bms

So if solar panel would produce more than 4v it would convert it to 16 v which would charge bms - bateries.
 

Martaine2005

May 12, 2015
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Hoora for Cricklewood electronics!. These great shops are dying by the dozen.

Martin
 

Bluejets

Oct 5, 2014
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So if solar panel would produce more than 4v it would convert it to 16 v which would charge bms - bateries.
Don't start out as a "free energy" geek.
One good rule to remember, surprised you haven't learnt it yet, energy out is equal to energy in , minus losses.
 

Lziga55

Oct 2, 2023
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Don't start out as a "free energy" geek.
One good rule to remember, surprised you haven't learnt it yet, energy out is equal to energy in , minus losses.
I know I just want to try and learn something. I just dont know if this what i said before would work. And I know that there are cheaper products available, but where is all the fun it buying stuff ;)
 

Alec_t

Jul 7, 2015
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but where is all the fun in buying stuff ;)
It's more fun than the fire or explosion which could result from messing about with a home-brew design if not built properly. Lithium batteries are dangerous if not charged and discharged correctly.
 

Lziga55

Oct 2, 2023
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It's more fun than the fire or explosion which could result from messing about with a home-brew design if not built properly. Lithium batteries are dangerous if not charged and discharged correctly.
That is why i will use bms
 

Lziga55

Oct 2, 2023
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Thanks!
What do you think about this module:
Just found this amazing item on AliExpress. Check it out! €1.84 12%OFF | TZT 3.7V 4.2V Charger 5V 6V 9V 12V Discharger Board DC DC Converter Boost Module For Diy Solar Mobile Power Charger Module
I want to try and build something or connect together ;) and i think that this would work!
 

Delta Prime

Jul 29, 2020
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and i think that this would work!
Prove to yourself that it will work do not think! Know!
I'm being the devil's advocate here! It will not work.
For the sake of your little house on the hill. there's no way around it he must do the math.
1693095146518.jpg
 
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